RBSE Solutions Class 9 Science Chapter 6 Structure of Living Organisms

Structure of Living Organisms

Structure of Living Organisms Textbook Questions Solved

Objective Type Questions

 

Question 1. Which organelle of the cell is known as Suicidal Bag?
(A) Mitochondria
(B) Lysosome
(C) Ribosome
(D) Golgi body
Answer: (B) Lysosome
In simple words: Lysosomes are like the recycling centers of a cell. They contain strong enzymes that can break down waste materials and old cell parts. If a cell is damaged beyond repair, lysosomes can break down the whole cell, which is why they are called "suicidal bags."

🎯 Exam Tip: Remember that lysosomes are key for cellular waste disposal and their enzymes are crucial for this function, leading to their common nickname.

 

Question 2. Which organelle of the cell is known as the powerhouse of the cell?
(A) Mitochondria
(B) Lysosome
(C) Ribosome
(D) Nucleus
Answer: (A) Mitochondria
In simple words: Mitochondria are responsible for creating most of the energy a cell needs to function. They make a special energy molecule called ATP, which acts like fuel for the cell's activities. That's why they are known as the "powerhouse."

🎯 Exam Tip: When asked about energy production in a cell, mitochondria should be your immediate answer, as they generate ATP through cellular respiration.

 

Question 3. Which scientist discovered the nucleus?
(A) Robert Brown
(B) Robert Hook
(C) Leuwen hock
(D) Schliden
Answer: (A) Robert Brown
In simple words: Robert Brown was the person who first saw and named the nucleus inside a cell. This discovery was important because the nucleus acts like the control center of the cell.

🎯 Exam Tip: It's important to remember key scientists and their discoveries, such as Robert Brown for the nucleus and Robert Hooke for 'cells'.

 

Question 4. In which phase of cell cycle, DNA is synthesised:
(A) G - I phase
(B) Anaphase
(C) M phase
(D) S-phase
Answer: (D) S-phase
In simple words: The cell cycle has different steps, and the S-phase is when the cell makes a copy of all its DNA. This copying is essential so that when the cell divides, each new cell gets a complete set of genetic information.

🎯 Exam Tip: The cell cycle involves interphase (G1, S, G2) and M phase. The S-phase (Synthesis phase) is specifically for DNA replication, ensuring genetic continuity.

Structure of Living Organisms Very Short Answer Type Questions

 

Question 6. Name the scientist who saw the living cell, for the first time?
Answer: Antonie van Leeuwenhoek was the first scientist to observe living cells. He used his own crafted single-lens microscopes to see tiny organisms. This observation marked a significant milestone in biology.
In simple words: Leeuwenhoek was the first scientist to see living cells using his microscope.

🎯 Exam Tip: Differentiate between Robert Hooke (who observed dead cork cells and coined 'cell') and Antonie van Leeuwenhoek (who observed living cells like bacteria and protozoa).

 

Question 7. Name any two unicellular organisms?
Answer: Two unicellular organisms are:
(a) Amoeba
(b) Chlamydomonas
These organisms are made up of only one cell, which performs all life functions.
In simple words: Amoeba and Chlamydomonas are two examples of living things that are made of just one cell.

🎯 Exam Tip: Unicellular organisms are simple life forms where a single cell handles all biological processes, unlike multicellular organisms.

 

Question 8. Name the largest cell of the human body?
Answer: The largest cell of the human body is the Neuron, also known as a nerve cell. These cells can be very long, extending from the spinal cord to the tips of the toes, helping to transmit signals over long distances.
In simple words: The neuron, or nerve cell, is the longest cell in the human body.

🎯 Exam Tip: While an ovum (egg cell) is the largest in volume, neurons are generally considered the longest in terms of length due to their axons.

 

Question 9. What is the function of the cell wall in a plant cell?
Answer: The cell wall in a plant cell has several key functions:
(a) It gives rigidity, structural strength, and a definite shape to the cell. This outer layer helps the plant stand upright and resist pressure.
(b) It helps in the transport of various substances across it, acting as a filter and providing protection.
In simple words: The cell wall makes plant cells strong and gives them a clear shape. It also helps things move in and out of the cell.

🎯 Exam Tip: Remember that the cell wall is unique to plant cells (and some other organisms) and provides essential structural support and protection, unlike animal cells which only have a cell membrane.

 

Question 10. On the basis of pigments, how many types of plastids are present in plants?
Answer: Based on the types of pigments they contain, plastids in plants are mainly of three types:
(i) Chromoplasts: These are colored plastids (other than green) that give color to flowers and fruits. For example, the red color in tomatoes.
(ii) Chloroplasts: These are green-colored plastids that contain chlorophyll and are responsible for photosynthesis.
(iii) Leucoplasts: These are colorless plastids that store food materials like starch, oils, and proteins.
In simple words: Plastids in plants come in three types based on color: chromoplasts for other colors, chloroplasts for green and making food, and leucoplasts for storing food and being colorless.

🎯 Exam Tip: Understand the primary function of each plastid type: chloroplasts for photosynthesis, chromoplasts for colors, and leucoplasts for storage. This functional diversity is vital for plant life.

 

Question 11. What is the function of the ribosome in a cell?
Answer: The main function of ribosomes in a cell is to synthesize proteins. These tiny organelles read genetic instructions and build proteins, which are vital for almost all cellular activities. Both ribosomes that are attached to the endoplasmic reticulum and those floating freely in the cytoplasm are involved in this protein production.
In simple words: Ribosomes in a cell are like tiny factories that make proteins. Proteins are very important for the cell to work.

🎯 Exam Tip: Always remember that ribosomes are the "protein factories" of the cell; this is their core and most critical role.

 

Question 12. What type of division takes place in somatic cells?
Answer: In somatic cells, which are all body cells except reproductive cells, mitosis-cell division takes place. Mitosis produces two identical daughter cells, maintaining the same number of chromosomes as the parent cell. This process is essential for growth and repair.
In simple words: Mitosis is the type of cell division that happens in normal body cells. It makes two new cells that are exactly like the first one.

🎯 Exam Tip: Distinguish between mitosis (for growth and repair in somatic cells, producing identical diploid cells) and meiosis (for sexual reproduction in germ cells, producing haploid cells with half chromosomes).

 

Question 13. Why meiosis division is known as a reductional division?
Answer: Meiosis division is known as reductional division because during the first division of meiosis, the chromosomal number in the daughter cells is reduced to half compared to the parent cell. This process produces two haploid cells from a single diploid cell, which is crucial for sexual reproduction to maintain the species' chromosome count. For example, humans have 46 chromosomes, and after meiosis, egg and sperm cells each have 23.
In simple words: Meiosis is called "reductional division" because it cuts the number of chromosomes in half. This is important for making reproductive cells like sperm and egg cells.

🎯 Exam Tip: The key characteristic of meiosis as reductional division is the halving of chromosome number, which is vital for preventing chromosome doubling in sexually reproducing organisms.

 

Question 14. In plants during cell division, cytoplasm is divided in which phase?
Answer: In plants during cell division, the division of the cytoplasm occurs after karyokinesis (nuclear division) in the cytokinesis phase of mitosis. This is the final step where the single parent cell physically splits into two separate daughter cells, each with its own cytoplasm and organelles.
In simple words: In plant cells, the cytoplasm divides during the cytokinesis phase, right after the nucleus has divided.

🎯 Exam Tip: Remember that cell division has two main parts: karyokinesis (nucleus division) and cytokinesis (cytoplasm division). They always happen in that order.

 

Question 15. Which type of substance is deposited on the cell wall of collenchyma tissue?
Answer: Cellulose and Pectin are the substances deposited on the cell wall of collenchyma tissue. These deposits are typically found at the corners of the cells, providing flexible support and strength to young plant parts, like stems and leaf stalks. This gives collenchyma its characteristic strong yet flexible nature.
In simple words: Cellulose and Pectin are the materials found on the cell walls of collenchyma tissue, making them strong and flexible.

🎯 Exam Tip: Note that lignin is absent in collenchyma, which allows it to provide flexible support, distinguishing it from sclerenchyma that has lignin for rigid support.

Structure of Living Organisms Short Answer Type Questions

 

Question 16. What are unicellular and multicellular organisms? Give example.
Answer: Unicellular organisms are living things made up of only one cell. This single cell performs all the necessary life functions, such as taking in food, breathing, and reproducing. An example is the Amoeba, a tiny organism found in water. Multicellular organisms, on the other hand, are composed of many cells that work together. These cells are specialized for different jobs, forming tissues, organs, and organ systems. Examples include a cat, a dog, and humans, where various cells cooperate to form a complete living being.
In simple words: Unicellular organisms have only one cell, like an Amoeba. Multicellular organisms have many cells working together, like a cat or a human.

🎯 Exam Tip: The key difference is the number of cells and the degree of specialization; unicellular organisms rely on one cell for everything, while multicellular organisms have cells performing specific tasks.

 

Question 17. Explain the cell theory?
Answer: Cell theory is a fundamental concept in biology that explains what cells are and their role in living organisms. It states that a cell is the smallest unit of structure and function in any living organism. German scientists M.J. Schleiden and Theodor Schwann first proposed this theory. Later, Rudolf Virchow expanded it by adding that all cells come from pre-existing cells. This idea helped us understand how life grows and reproduces. The modern version of cell theory summarizes these points clearly.
Thus the modern version of the cell theory summarized as follows:
1. All living things, whether plants or animals, are composed of cells and their products.
2. A cell is the smallest unit of structure and function, which arise from pre-existing cells, and its continuity is maintained through genetic material.
3. All cells are basically alike, found after chemical analysis and studying the functions of different components.

Following are the concepts of the modern cell theory:
1. The body of each living being is composed of one or more cells and cell products.
2. The cell is the fundamental unit of all biochemical reactions.
3. A cell is also a hereditary unit because it contains genetic material in it.
4. New cells are formed from the division of pre-existing cells.
5. All organisms start life from a single cell.
6. All organisms function through the activities of cells.
In simple words: Cell theory says that all living things are made of cells, cells are the basic units of life, and new cells always come from old cells. It also highlights that cells are where all life activities happen and they carry genetic information.

🎯 Exam Tip: When explaining cell theory, ensure you include the three main tenets: all organisms are made of cells, cells are the basic unit of life, and all cells come from pre-existing cells.

 

Question 18. Explain the structure and function of Mitochondria?
Answer: Mitochondria are small, oval or rod-shaped organelles found in large numbers within cells. They are often called the "powerhouse of the cell" because they generate most of the cell's energy. A mitochondrion has two membranes: an outer membrane and a folded inner membrane, called cristae. These folds create more surface area for chemical reactions. Inside, it contains a jelly-like substance called the matrix.

A mitochondrion consists of:
1. an outer membrane
2. an inner membrane with folds called cristae
3. the matrix (internal fluid)

These structures help it perform its main functions:
1. It generates energy for various activities of the cell. Mitochondria take in nutrients and break them down to create energy.
2. Whenever the cell requires energy, ATP (adenosine triphosphate) molecules are broken down, releasing energy for the body to make chemical compounds and perform mechanical work. ATP is like the cell's energy currency.
3. Mitochondria have their own DNA and ribosomes; therefore, they can make some of their own proteins, making them semi-autonomous organelles.
In simple words: Mitochondria are little cell parts that make energy for the cell to do its work. They have two walls, with the inner one being folded. They even have their own special DNA and can make some of their own proteins.

🎯 Exam Tip: Emphasize the "powerhouse" analogy and connect it to ATP production. Mentioning their double membrane and independent DNA is crucial for a complete answer.

 

Question 19. Write the four difference between Animal and Plant cell?
Answer: Here are four key differences between animal and plant cells:

In simple words: Plant cells are bigger, square-shaped, have a strong cell wall, and have green plastids and a large storage sac called a vacuole. Animal cells are smaller, rounder, do not have a cell wall or plastids, and have small or no vacuoles.

🎯 Exam Tip: Focus on the most distinct features: cell wall and chloroplasts in plants, and centrioles in animals. Vacuole size and shape are also good distinguishing points.

 

Question 20. Why lysosomes are known as suicide bags?
Answer: Lysosomes are called "suicide bags" because they contain powerful hydrolytic enzymes that can digest and break down various organic materials, including damaged cell components and entire cells. If a cell is old, injured, or diseased, its lysosomes can burst and release these enzymes, leading to the self-digestion of the cell. This process is like a controlled self-destruction, which helps in removing unwanted or unhealthy cells, making way for new, healthy ones. This mechanism is crucial for cellular health and renewal.
In simple words: Lysosomes are called "suicide bags" because they hold strong chemicals that can break down the cell itself if it gets old or damaged. This helps clean out bad cells.

🎯 Exam Tip: The key to this answer is the presence of powerful digestive enzymes within lysosomes, which allow them to break down cellular components, including the cell itself.

 

Question 21. Describe the structure and function of the nucleus?
Answer: The nucleus is a large, spherical or oval-shaped organelle that acts as the control center of a eukaryotic cell. It was discovered by Robert Brown in 1831 and usually sits in the center of the cell. The nucleus is made up of several important parts: a nuclear membrane, nucleoplasm, chromatin material, and the nucleolus.

1. Nuclear membrane: This is a double-layered membrane that surrounds the nucleus. It has tiny holes called nuclear pores, which allow materials to move between the nucleus and the cytoplasm.

2. Nucleoplasm: This is a thick, jelly-like fluid inside the nucleus. It contains a network of fine threads called chromatin, which, during cell division, forms structures called chromosomes. The nucleoplasm also contains the nucleolus.

3. Chromosomes: These are thread-like structures made of specific proteins and deoxyribose nucleic acid (DNA). Genes, which control hereditary characters, are segments of DNA located on chromosomes. The number of chromosomes is constant for each species.

4. Nucleolus: This is a small, round body inside the nucleus, rich in RNA (ribonucleic acid). The nucleolus is important for making ribosomes, which are essential for protein synthesis.
The functions of the nucleus are as follows:

• The nucleus controls all the activities of the cell through its DNA molecules.
• It helps in cell division.
• Genes on chromosomes carry hereditary characters from one generation to another generation.
• The nucleolus helps in protein synthesis by forming ribosomes.

In simple words: The nucleus is the cell's main controller. It has a double wall (nuclear membrane) with holes. Inside, it has a jelly-like fluid (nucleoplasm) with DNA threads (chromatin) that become chromosomes. It also has a nucleolus, which helps make proteins. The nucleus stores all genetic information and directs cell activities.

🎯 Exam Tip: Focus on the nucleus as the 'brain' of the cell, emphasizing its role in storing genetic material (DNA in chromosomes) and controlling cell activities, including protein synthesis via the nucleolus.

 

Question 23. Explain the method of cytokinesis in plant and animal cell?
Answer: Cytokinesis is the final stage of cell division where the cytoplasm divides, forming two distinct daughter cells. This process happens differently in animal and plant cells after karyokinesis (nuclear division) is complete.

• In animal cells: Toward the end of telophase, a shallow groove called a cleavage furrow appears on the cell surface, precisely in the middle. This furrow gradually deepens and pinches the cell membrane inward, eventually dividing the cytoplasm and creating two daughter cells. This is like tightening a belt around a balloon.
• In plant cells: After karyokinesis, small membrane-bound sacs called vesicles gather in the middle of the cell, forming a row. These vesicles fuse to create a cell plate. This cell plate then grows outward until it reaches the existing cell walls, forming a new cell wall that completely divides the two daughter cells. This new cell wall provides structural integrity to the new plant cells.

The formation of cell wall divides the cell into two:
Plant Cell:

• No centriole present
• No aster forms
• Cell plate forms
• No furrowing of cytoplasm at cytokinesis
• Occurs mainly at meristems.

Animal Cell:

• Centrioles are present
• Asters are formed
• Cleavage furrow forms
• Furrowing of cytoplasm at cytokinesis
• Occurs throughout the body for growth and repair.

In simple words: In animal cells, the cell pinches in the middle to split into two. In plant cells, a new wall is built from the inside out to divide the cell.

🎯 Exam Tip: Clearly differentiate between the cleavage furrow method in animal cells and the cell plate formation method in plant cells. This is a common point of comparison.

 

Question 24. Explain the metaphase of the mitotic division with a diagram?
Answer: Metaphase is a crucial stage of mitotic division where all the chromosomes align themselves precisely at the center of the cell, forming a structure called the metaphase plate or equatorial plate. This plate is an imaginary plane equidistant from the two poles of the spindle.

During metaphase, each chromosome, consisting of two sister chromatids, is attached to spindle fibers at its centromere. The centromeres of the chromosomes lie along the equator, while the chromatids extend freely into the surrounding cytoplasm. This arrangement ensures that when the chromatids separate in the next phase, each new cell receives an identical set of chromosomes. This precise alignment is facilitated by the spindle fibers, which are made of microtubules. In animal cells and lower plants, centrioles and asters (astral mitosis) are present, which help organize the spindle fibers. Higher plants, however, have anastral mitosis, lacking centrioles and asters.

Metaphase is shorter than prophase but longer than anaphase, ensuring accurate chromosome distribution.


In simple words: In metaphase, all the chromosomes line up neatly in the middle of the cell, forming a line. They get ready to be pulled apart equally into new cells.

🎯 Exam Tip: The key event in metaphase is the alignment of chromosomes at the metaphase plate (equator), which is vital for equal distribution to daughter cells.

 

Question 25. Explain the Anaphasic Movement in cell division?
Answer: Anaphasic movement occurs during anaphase, a phase of cell division where the sister chromatids of each chromosome rapidly separate and move towards opposite poles of the cell. This movement begins when the centromere, which holds the sister chromatids together, splits into two. Each chromatid then becomes an individual daughter chromosome.

The force behind this movement comes from two main actions: the repulsion between the newly separated centromeres, and the contraction of the spindle fibers (microtubules) that are attached to them. As the spindle fibers shorten, they pull the daughter chromosomes to opposite ends of the cell. This ensures that each new cell formed after division receives a complete and identical set of genetic material.
In simple words: Anaphasic movement is when the two halves of each chromosome (sister chromatids) pull apart and move to opposite sides of the cell. This happens because the middle part splits and the pulling fibers get shorter.

🎯 Exam Tip: The defining characteristic of anaphase is the separation of sister chromatids and their movement to opposite poles. Emphasize the role of centromere splitting and spindle fiber contraction.

 

Question 27. Explain the structure and functions of Xylem?
Answer: Xylem is a complex permanent tissue in plants that plays a crucial role in transporting water and dissolved mineral salts from the roots up to the leaves. It also provides structural support to the plant.

Structural elements of xylem:

• Tracheids: These are long, slender, dead cells with thick, lignified walls. They have large cavities and are responsible for water conduction and mechanical support. They can be annular, spiral, reticulate, scalariform, and pitted, depending on their wall thickenings.
• Vessels: These are broader and shorter than tracheids. They are composed of many cells joined end to end, forming continuous tubes. Their walls are also lignified and perforated, making them efficient water conduits.
• Xylem Fibers (Wood fibers): These are sclerenchyma fibers present in xylem. They are dead cells with thick walls, primarily providing mechanical strength to the plant.
• Xylem Parenchyma (Wood parenchyma): These are living parenchyma cells within the xylem. They have thinner walls compared to other xylem elements and are involved in storing food and helping with the sideways (lateral) conduction of sap or water.

Functions of each of the elements are:

• Water and minerals: Xylem conducts water and minerals vertically upwards from the roots to all parts of the plant.
• Support: The lignified walls of xylem elements provide mechanical support, helping the plant to stand upright.
• Storage: Xylem parenchyma stores food, and in some cases, also helps in lateral conduction of water.

In simple words: Xylem is a plant tissue that carries water and minerals from the roots up to the leaves. It also helps to keep the plant strong. It is made of different types of cells like tracheids, vessels, and fibers.

🎯 Exam Tip: Remember xylem's two main roles: water transport (from roots to leaves) and structural support. Distinguish between its dead (tracheids, vessels, fibers) and living (parenchyma) components.

 

Question 28. Draw a labelled diagram of a neuron.
Answer: Neurons, or nerve cells, are specialized cells that transmit electrical and chemical signals throughout the body. They are the fundamental units of the nervous system. A typical neuron consists of three main parts: a cell body (soma), dendrites, and an axon. The axon is often covered by a myelin sheath, which helps speed up signal transmission.

Diagram of a Neuron:

In simple words: A neuron is a special cell that sends messages. It has a main body with a nucleus, branch-like parts called dendrites that receive signals, and a long tail called an axon that sends signals.

🎯 Exam Tip: When drawing a neuron, ensure clear labels for the cell body (soma), nucleus, dendrites, axon, myelin sheath, Node of Ranvier, and axon terminals, as these are the key structural components.

 

Question 29. Describe the various muscles found in Animals?
Answer: Animal bodies contain different types of muscle tissues, which are responsible for movement and various internal functions. These muscles are made of elongated cells called muscle fibers and contain special proteins called contractile proteins that allow them to contract and relax. There are three main types of muscular tissues:

(a) Striated muscle (Skeletal/Voluntary muscle): These muscles are attached to bones and are responsible for movements we can control, like walking or lifting. Their cells are long, cylindrical, unbranched, and have multiple nuclei. Under a microscope, they show alternating light and dark bands (striations).

(b) Smooth muscle (Unstriated/Involuntary muscle): These muscles work automatically without our conscious control. They are found in internal organs like the stomach, intestines, and blood vessels, controlling functions such as digestion and blood flow. Their cells are long, spindle-shaped, have a single nucleus, and do not show any striations.

(c) Cardiac muscle: This specialized muscle tissue is found only in the heart. It is involuntary, meaning it works continuously without conscious effort, performing rhythmic contractions and relaxations throughout life to pump blood. Cardiac muscle cells are cylindrical, branched, and usually have one nucleus per cell.
In simple words: Animals have three kinds of muscles: striated muscles for movements we control (like arms), smooth muscles for automatic movements in organs (like digestion), and cardiac muscles only in the heart for pumping blood.

🎯 Exam Tip: Clearly differentiate the three muscle types based on location, control (voluntary/involuntary), and presence/absence of striations. Remember that cardiac muscle is unique to the heart.

 

Question 30. Explain the structure of Virus? Draw a labelled diagram of Bacteriophage.
Answer: Viruses are microscopic infectious agents that can only replicate inside the living cells of other organisms. They are not considered living organisms because they lack cellular machinery and depend entirely on a host cell for reproduction. Viruses generally consist of genetic material (DNA or RNA, but never both) enclosed within a protein coat called a capsid. This genetic material can be single-stranded or double-stranded.

Bacteriophages are a specific type of virus that infects bacteria. They typically have a complex structure, often described as tadpole-like, with a distinct head and tail. The head is usually hexagonal and contains the viral genetic material (often double-stranded DNA), tightly packed within the protein capsid. The tail is cylindrical and made of proteins, which helps the virus attach to and inject its genetic material into the bacterial host.

Diagram of a Bacteriophage:

In simple words: A virus is a tiny particle with DNA or RNA inside a protein coat. It needs to enter a living cell to make copies of itself. A bacteriophage is a type of virus that looks like a tiny spaceship, with a head and a tail, and it infects bacteria.

🎯 Exam Tip: Remember that viruses are non-cellular, parasitic, and consist of genetic material (DNA or RNA) inside a protein coat. A bacteriophage is a classic example due to its distinct head-and-tail structure.

Structure of Living Organisms Long Answer Type Questions

 

Question 31. Draw a labelled diagram of a plant cell? Explain the structure and function of the following organelles? (a) Chloroplast (b) Endoplasmic reticulum (c) Mitochondria (d) Nucleus
Answer: A plant cell is a fundamental unit of plant life, typically larger than an animal cell and characterized by the presence of a cell wall, plastids, and a large central vacuole. Unlike animal cells, plant cells lack centrosomes and centrioles. They have distinct organelles that perform specialized functions essential for plant growth and survival.

Plant cell:

Structure and functions of organelles:
(a) Chloroplast:
Structure: Chloroplasts are green, oval-shaped organelles in plant cells, enclosed by two membranes. Inside, they have a colorless fluid matrix called stroma and a system of internal membranes called thylakoids, which are stacked into structures called grana. Thylakoids contain chlorophyll and other pigments that capture light energy.
Function: Chloroplasts are the sites of photosynthesis. They trap solar energy using chlorophyll and convert it into chemical energy, producing food (sugars) for the plant. This is why they are often called the "kitchen of the cell."


(b) Endoplasmic reticulum (ER):
Structure: The ER is a vast network of interconnected membrane-bound channels or sacs that extend throughout the cytoplasm. It can be smooth (SER) or rough (RER). RER has ribosomes attached to its surface, giving it a bumpy appearance, while SER lacks ribosomes. Both types are important for different cell functions.
Functions:

• The ER acts as a circulatory system for the cell, helping in the quick transport of materials within the cell.
• It provides structural support, acting as a skeletal framework for the cell.
• RER is primarily involved in synthesizing and folding proteins, especially those destined for secretion or insertion into membranes.
• SER is involved in the synthesis of lipids (fats), steroids, and carbohydrates. It also plays a role in detoxifying drugs and poisons and forming visual pigments.

(c) Mitochondria:
Structure: Mitochondria are small, rod-shaped or spherical organelles, often called the "powerhouse" of the cell. They are enclosed by two membranes: a smooth outer membrane and a highly folded inner membrane called cristae. These folds increase the surface area for chemical reactions. The inner compartment is filled with a gel-like substance called the matrix.
Function: Mitochondria are the primary sites of cellular respiration. They break down food molecules to release energy, which is stored in ATP (adenosine triphosphate) molecules. This ATP is then used to power most of the cell's activities, from building new compounds to performing mechanical work.

(d) Nucleus:
Structure: The nucleus is a large, spherical or oval-shaped organelle, usually located in the center of the cell. It contains the cell's genetic material. It is surrounded by a double-layered nuclear membrane with pores. Inside, it has a jelly-like nucleoplasm, chromatin (DNA and proteins), and a nucleolus.
Function: The nucleus controls all cellular activities by regulating gene expression. It stores the cell's genetic information (DNA) in chromosomes and is responsible for passing hereditary traits from one generation to the next. The nucleolus within the nucleus is involved in ribosome synthesis, which is crucial for protein production.
In simple words: A plant cell has a strong wall, a large central vacuole, and green chloroplasts for making food. The endoplasmic reticulum helps move things and make proteins/fats. Mitochondria make energy for the cell. The nucleus controls the cell and holds its genetic information.

🎯 Exam Tip: For each organelle, remember its defining structural features (e.g., double membrane, folds, ribosomes) and its primary function. Emphasize how each part contributes to the cell's overall life processes.

 

Question 32. What is Mitosis? Explain the different phases of mitosis division with a labelled diagram.
Answer: Mitosis is a type of cell division. In this process, one cell divides into two new cells, called daughter cells. Each new cell gets the same number of chromosomes as the original parent cell. This ensures that genetic information is passed on correctly.
Phases of Mitosis:
(i) Interphase: This is the stage before mitosis starts. During interphase, the cell grows, and its DNA and chromosomes copy themselves. This preparing phase occurs between the end of one cell division and the start of the next.
(ii) Karyokinesis: This is the division of the cell's nucleus. It involves several main stages:
- Prophase: In this stage, the chromosomes become visible as thick, coiled threads. They also shorten and become thicker.
- Metaphase: The chromosomes line up in the very middle of the cell. This central area is called the equatorial or metaphase plate.
- Anaphase: This is the third stage of nucleus division. Each chromosome splits into two identical parts, called sister chromatids. These new daughter chromosomes then move towards opposite ends (poles) of the cell. This movement happens because of the spindle fibers pulling them apart.
- Telophase: After reaching the poles, the daughter chromosomes uncoil and become less visible. A new nuclear membrane forms around each set of chromosomes, creating two distinct daughter nuclei. The cell prepares for final division.
(iii) Cytokinesis: This is the final step, where the cytoplasm of the cell divides.
- In animal cells, a furrow forms in the middle of the cell, which deepens until the cell splits into two.
- In plant cells, small membrane-bound sacs form a line in the middle, fusing to create a cell plate. This plate then develops into a new cell wall, dividing the cell into two.
(Note: The labelled diagram is omitted as per the content processing rules for non-geometric/Venn figures.)
In simple words: Mitosis is how one cell makes two identical cells. It involves copying DNA and then carefully splitting the nucleus and the rest of the cell into two parts, going through steps like prophase, metaphase, anaphase, and telophase.

🎯 Exam Tip: When explaining mitosis, clearly define each phase and describe the key events happening with the chromosomes. Though the diagram is omitted here, always be prepared to draw and label it in an exam.

 

Question 33. Define Tissues? Describe the simple tissues found in plants with a diagram?
Answer: A tissue is a collection of similar cells that work together to perform a specific function and share a common origin. For example, blood, phloem, and muscles are all types of tissues in living organisms.
Simple Tissues in Plants:
Simple tissues in plants are made up of only one type of cell, and these cells are similar in their structure and function. There are three main types of simple tissues:
(i) Parenchyma: This is the simplest type of plant tissue. Parenchyma cells are generally unspecialized, have thin cell walls, and are loosely packed, leaving small spaces between them. These tissues help support the plant, store food, and allow gases to exchange.
(ii) Collenchyma: Collenchyma is a strong yet flexible tissue. Its cells are living and have thick walls, especially at their corners, due to deposits of cellulose and pectin. There are no spaces between collenchyma cells. They can be round, oval, or many-sided. Collenchyma provides structural support and flexibility to young plant parts.
(iii) Sclerenchyma: Sclerenchyma is a very strong tissue that helps to stiffen and protect the plant. Its cells are dead when mature and have very thick, rigid walls due to a waterproof substance called lignin. There are no intercellular spaces. Sclerenchyma cells come in two forms: long, narrow fibers and shorter, irregular cells called sclereids. This tissue acts as a mechanical support and protective layer.
(Note: The labelled diagrams for parenchyma, collenchyma, and sclerenchyma are omitted as per the content processing rules for non-geometric/Venn figures.)
In simple words: Tissues are groups of similar cells working together. In plants, simple tissues like parenchyma (for storage and support), collenchyma (for flexible support), and sclerenchyma (for strong protection) are each made of one type of cell.

🎯 Exam Tip: Clearly state the definition of a tissue and then elaborate on each type of simple plant tissue, highlighting their cell characteristics, functions, and presence in different plant parts. Remember that simple tissues are made of *one* type of cell.

 

Question 34. Describe the various tissues found in animals?
Answer: Multicellular animals have four main types of tissues that perform different jobs:
(i) Epithelial Tissue: This tissue forms protective coverings for the body, both on the outside (like skin) and lining internal cavities such as the mouth, stomach, and lungs. Epithelial cells are packed tightly together with very little space or material between them. They do not have their own blood supply but do have nerve supply. These cells are attached to other tissues by a basement membrane, made of collagen fibers. Epithelium can be a single layer of cells or multiple layers.
(ii) Connective Tissue: This tissue supports, binds, and packs different tissues and organs together throughout the animal body. It has a large amount of non-living material called matrix, in which cells are embedded. The matrix can be semi-fluid, rigid, or gelatinous. Connective tissue contains fibers like white collagen and yellow elastin, and it helps to ingests bacteria and produces proteins.
(iii) Muscular Tissue: Muscle tissues are made of long, specialized muscle cells called muscle fibers, which can contract. They help in various body movements and locomotion. There are three types of muscular tissues:
- Striated Muscles: Also known as voluntary or skeletal muscles, these are attached to bones and allow us to move parts of our body by conscious will. Their cells are long, cylindrical, unbranched, and have many nuclei. Under a microscope, they show alternating light and dark bands (striations). They are found in limbs, the body wall, face, and neck.
- Unstriated Muscles: Also called smooth or involuntary muscles, we cannot move these muscles by conscious will. They control actions like food movement in the digestive system, blood vessel contraction, and iris movements in the eye. Their cells are long, spindle-shaped, with pointed ends and a single nucleus. They do not show any striations.
- Cardiac Muscles: These are involuntary muscles found only in the heart. Their cells are branched, cylindrical, and have a single nucleus. Cardiac muscles contract and relax rhythmically throughout life to pump blood to all parts of the body.
(iv) Nervous Tissue: This tissue is highly specialized to respond to stimuli and quickly transmit signals throughout the body. The brain, spinal cord, and nerves are all made of nervous tissue, specifically nerve cells called neurons. Each neuron has three main parts: the cyton (cell body), dendrites (short, branched fibers that receive signals), and an axon (a long fiber that transmits signals away from the cell body).
In simple words: Animals have four main tissue types: epithelial (for covering), connective (for support and binding), muscular (for movement), and nervous (for sending signals). Each type has special cells and does a different job to keep the body working.

🎯 Exam Tip: For each animal tissue type, remember its primary function, key cell characteristics (shape, nucleus, presence of matrix/fibers), and examples of where it's found in the body. Using clear, distinct examples for each type helps in scoring well.

 

Question 35. Write a short note on: (a) Vascular bundles (b) Nervous tissue (c) Bacteriophage (d) Sclerenchyma
Answer:
(a) Vascular bundles: These are plant structures formed from procambium, which comes from the apical meristem. Each vascular bundle is made of xylem (which transports water) and phloem (which transports food). Vascular bundles can be of two types, depending on whether cambium is present:
1. Open Vascular bundle: These bundles have cambium located between the xylem and phloem, commonly found in dicotyledons.
2. Closed Vascular bundle: These bundles do not have cambium, typically found in monocotyledons.
Vascular bundles are essential for the transport system in plants, allowing water and nutrients to move efficiently.
(b) Nervous tissue: This tissue is highly specialized to receive stimuli and quickly transmit nerve impulses throughout the body. It forms the brain, spinal cord, and all nerves. The cells of nervous tissue are called neurons or nerve cells. Each neuron has three parts:
1. Cyton (Cell body): This is the main part of the nerve cell, containing a large central nucleus and cytoplasm, from which hair-like parts extend.
2. Dendrite: These are short, branched fibers of the neuron that receive nerve impulses from other cells.
3. Axon: This is a single, long fiber that carries nerve impulses away from the cell body to other neurons or effector organs.
This tissue allows for rapid communication and coordination in the body.
(c) Bacteriophage: Bacteriophages are a type of virus that infects bacteria. They are structurally similar to other viruses, made of protein and nucleic acid (DNA or RNA). Unlike other viruses, they specifically use bacteria as their host cells. A bacteriophage often has a tadpole-like shape, with a hexagonal head and a cylindrical tail. The head contains its tightly packed double-stranded DNA within a protein coat. The tail has a hexagonal spiked end plate and tail fibers, which help it attach to bacterial cells. These viruses play an important role in controlling bacterial populations in nature.
(Note: The labelled diagram of Bacteriophage is omitted as per the content processing rules for non-geometric/Venn figures.)
(d) Sclerenchyma: This is a strengthening and protective plant tissue. Its cells are dead at maturity and have very thick, rigid walls made hard by a chemical called lignin, which is waterproof. Sclerenchyma cells have no spaces between them. This tissue makes plant parts hard and stiff, like the husk of a coconut. It provides strength, allows plants to bear stress, and forms a protective covering around seeds and nuts, giving the plant body rigidity, flexibility, and elasticity.
In simple words: Vascular bundles move water and food in plants. Nervous tissue sends messages quickly through the body. Bacteriophages are viruses that infect bacteria. Sclerenchyma is a strong tissue that gives plants stiffness and protection.

🎯 Exam Tip: When writing short notes, define the term clearly, describe its key components or features, and briefly explain its function or significance. For biological structures, mention their location or typical form.

 

Structure Of Living Organisms Additional Questions Solved

Multiple Choice Questions (MCQs)

 

Question 1. The structureless fluid of cytoplasm is called as-
(a) Trophoplasm
(b) Protoplasm
(c) Hyaloplasm
(d) Metaplasm
Answer: (c) Hyaloplasm
In simple words: The clear, jelly-like liquid part of the cell's cytoplasm, which doesn't have any specific structures, is called hyaloplasm.

🎯 Exam Tip: Distinguish between cytoplasm (all contents inside the cell membrane, excluding the nucleus), protoplasm (all living parts of the cell, including cytoplasm and nucleus), and hyaloplasm (the fluid part of cytoplasm).

 

Question 2. The example of a Prokaryotic cell is -
(a) Blue-green algae.
(b) Fungi
(c) Chloroplast
(d) Animal
Answer: (a) Blue-green algae.
In simple words: Blue-green algae, also known as cyanobacteria, are simple cells that do not have a nucleus or other membrane-bound parts, which makes them prokaryotic.

🎯 Exam Tip: Remember that prokaryotic cells are simpler organisms (like bacteria and blue-green algae) without a true nucleus or membrane-bound organelles, unlike eukaryotic cells which have both.

 

Question 3. In which of the following DNA is found-
(a) Endoplasmic reticulum
(b) Ribosomes
(c) Chloroplast
(d) Golgi bodies
Answer: (c) Chloroplast
In simple words: DNA is mainly in the cell's nucleus, but small amounts are also found in mitochondria and chloroplasts, allowing them to make some of their own proteins.

🎯 Exam Tip: While the nucleus holds most of a cell's DNA, remember that chloroplasts and mitochondria also contain their own genetic material, which is a key characteristic of these organelles.

 

Question 5. The organelle related to Protein synthesis is-
(a) Chloroplus
(b) Centrosome
(c) Metaplast
(d) Ribosome
Answer: (d) Ribosome
In simple words: Ribosomes are like tiny factories in the cell that build all the proteins the cell needs to work properly.

🎯 Exam Tip: Ribosomes are universally known as the "protein factories" of the cell. Connect their function directly to protein synthesis.

 

Question 6. The cell theory of Schleiden and Schwann stated that
(a) cells are fundamental structural units of plants and animals
(b) all cells have nuclei
(c) all cells have a nucleolus
(d) cells reproduce by mitosis and meiosis
Answer: (a) cells are fundamental structural units of plants and animals
In simple words: The cell theory, first proposed by Schleiden and Schwann, states that all living things are made of cells and that cells are the most basic units of life.

🎯 Exam Tip: Recall the two main points of the original cell theory: all living organisms are composed of cells, and the cell is the basic unit of life. Virchow later added that all cells arise from pre-existing cells.

 

Question 7. A plant cell can be distinguished from an animal cell.
(a) By the presence of centrosome
(b) By the presence of cell wall
(c) By the presence of plasma membrane
(d) By the presence of small vacuoles
Answer: (b) By the presence of cell wall
In simple words: The most obvious way to tell a plant cell from an animal cell is that plant cells have a rigid cell wall, which animal cells do not.

🎯 Exam Tip: Key differences between plant and animal cells include the presence of a cell wall, chloroplasts, and a large central vacuole in plant cells, which are absent in animal cells (except for small, temporary vacuoles).

 

Question 8. Which cell organelle is called 'Protein Factory' and 'cell engine'?
(a) Golgi body
(b) Centrosome
(c) Lysosome
(d) Ribosome
Answer: (d) Ribosome
In simple words: Ribosomes are tiny parts inside cells that build all the proteins, making them the "protein factories" and essential "engines" for cell functions.

🎯 Exam Tip: Be precise with the common names of organelles. Ribosomes are consistently referred to as the "protein factories" due to their role in protein synthesis.

 

Question 10. Which of the following is a direct division-
(a) Mitosis
(b) Meiosis
(c) Amitosis
(d) None of the options
Answer: (c) Amitosis
In simple words: Amitosis is a simple way cells divide, where the nucleus splits directly without the complex steps seen in mitosis or meiosis.

🎯 Exam Tip: Remember that Amitosis is a less complex form of cell division, often seen in simpler organisms or specialized cells, where the nucleus divides directly without forming chromosomes or a spindle apparatus.

 

Question 11. In which phase DNA is synthesised-
(a) Growth period II
(b) Growth period I
(c) Synthesis period
(d) Division period
Answer: (c) Synthesis period
In simple words: The "Synthesis period," or S phase, is when a cell makes a copy of all its DNA before it divides.

🎯 Exam Tip: The cell cycle has distinct phases: G1 (Growth 1), S (Synthesis), G2 (Growth 2), and M (Mitosis). Associate the 'S' phase with DNA synthesis (replication).

 

Question 12. A cell has 4 chromosomes. After meiotic cell divisions, the number of chromosomes in the daughter cell will be-
(a) 4
(b) 2
(c) 16
(d) 32
Answer: (b) 2
In simple words: Meiotic cell division halves the number of chromosomes, so a cell starting with 4 chromosomes will produce daughter cells each having 2 chromosomes.

🎯 Exam Tip: Meiosis is known as "reductional division" because it reduces the chromosome number by half in the resulting daughter cells, which is crucial for sexual reproduction.

 

Question 13. Synapsis occurs during-
(a) Amitosis
(b) Mitosis
(c) Meiosis
Answer: (c) Meiosis
In simple words: Synapsis, where homologous chromosomes pair up, is a special event that only happens during meiosis.

🎯 Exam Tip: Synapsis is a defining feature of prophase I in meiosis, essential for crossing over and genetic recombination. It does not occur in mitosis or amitosis.

 

Question 15. The points where two of the four chromatids cross each other are known as-
(a) Chiasmata
(b) Centromere
(c) Chromomeres
(d) Homotypic
Answer: (a) Chiasmata
In simple words: When chromatids exchange genetic material, the points where they cross over are called chiasmata.

🎯 Exam Tip: Chiasmata are visible evidence of crossing over, a process unique to meiosis that increases genetic diversity.

 

Question 16. If chromosomes are at middle part in a line, then which will be the stage of mitosis-
(a) Telophase
(b) Metaphase
(c) Prophase
(d) Anaphase
Answer: (b) Metaphase
In simple words: When chromosomes line up neatly in the center of the cell, like a meeting point, that stage is called metaphase during cell division.

🎯 Exam Tip: Metaphase is characterized by the alignment of chromosomes at the equatorial plate. This orderly arrangement is crucial for ensuring equal distribution of genetic material to daughter cells.

 

Question 17. The tissue is a group of cells-
(a) Similar in origin but dissimilar in structure and function.
(b) Similar in origin, structure, and function.
(c) Similar in origin and structure but dissimilar in function.
(d) Dissimilar in structure, origin and function.
Answer: (b) Similar in origin, structure, and function.
In simple words: Tissues are collections of cells that come from the same place, look similar, and work together to do the same job.

🎯 Exam Tip: A key definition in biology: tissues are formed by cells that are alike in their origin, structure, and specifically function together as a unit.

 

Question 18. The chief function of phloem is the conduction of-
(a) food
(b) water
(c) mineral salts
(d) all of the options
Answer: (a) food
In simple words: Phloem is a special plant tissue that moves the food (sugars) made during photosynthesis from the leaves to all other parts of the plant where it's needed for energy or storage.

🎯 Exam Tip: Differentiate clearly between xylem (transports water and minerals from roots to leaves) and phloem (transports food/sugars from leaves to other parts) when discussing plant vascular tissues.

Structure of Living Organisms Very Short Answer Type Questions

 

Question 1. Where are proteins synthesised inside the cell?
Answer: Proteins are made inside the cell in small parts called ribosomes. These ribosomes act like tiny factories, building proteins that the cell needs. Proteins are vital for almost all cell functions.
In simple words: Ribosomes in the cell make proteins.

🎯 Exam Tip: Remember that ribosomes are often called the "protein factories" of the cell, which is a key concept.

 

Question 2. List the constituents of the plasma membrane.
Answer: The plasma membrane is primarily made up of two main components: proteins and lipids. These parts work together to form a barrier around the cell, controlling what goes in and out. This structure allows the cell to maintain its internal environment.
In simple words: The plasma membrane is made of proteins and lipids.

🎯 Exam Tip: Visualise the plasma membrane as a fluid mosaic of lipids and proteins, which helps to remember its composition and function.

 

Question 3. Name two cell organelles that have their own genetic material.
Answer: Two cell organelles that have their own genetic material are mitochondria and plastids. These organelles are unique because they can produce some of their own proteins, showing their evolutionary history as endosymbionts. They are often called semi-autonomous organelles.
In simple words: Mitochondria and plastids have their own genetic material.

🎯 Exam Tip: Keep in mind that having their own genetic material makes mitochondria and plastids special, similar to how bacteria operate.

 

Question 6. Which cell organelle is rich in acid, hydrolases?
Answer: Lysosomes are cell organelles that are rich in acid hydrolases. These enzymes are very important for breaking down waste materials and cellular debris. Lysosomes act like the cell's recycling centers, helping to keep it clean and functional.
In simple words: Lysosomes are full of enzymes called acid hydrolases.

🎯 Exam Tip: Relate lysosomes to "suicide bags" of the cell, as their enzymes can digest the cell itself if released.

 

Question 7. Which structure of animal cells forms the asters of the spindle?
Answer: Centrioles are the structures in animal cells that form the asters of the spindle during cell division. Asters help organize the spindle fibers, which are crucial for separating chromosomes correctly. This process ensures that new cells receive the right number of chromosomes.
In simple words: Centrioles in animal cells make the asters of the spindle.

🎯 Exam Tip: Remember that plant cells do not have centrioles, so their spindle formation mechanism is different.

 

Question 8. Write the name of different plant parts in which chloroplast, chromoplast and leucoplasts are present.
Answer:
1. Chloroplast-Green leaves, green stems and other green parts.
2. Chromoplast-Flower (petals) and fruits.
3. Leucoplast-Storage parts; such as roots, seeds, tubers etc. Plastids differentiate based on their functions, influencing plant color and storage. Each type plays a specific role in the plant's life.
In simple words: Chloroplasts are in green parts, chromoplasts are in colorful parts like flowers and fruits, and leucoplasts are in storage parts like roots.

🎯 Exam Tip: Understand that these plastids are interconvertible, meaning a chloroplast can become a chromoplast (e.g., ripening fruit).

 

Question 9. In which stage of cell division, DNA contents get doubled?
Answer: The DNA content gets doubled during the Interphase stage of cell division. Specifically, this happens in the S (Synthesis) phase of interphase, where DNA replication occurs. This crucial step ensures that each new cell receives a complete set of genetic material.
In simple words: DNA doubles in the Interphase stage, before the cell splits.

🎯 Exam Tip: Remember that interphase is a period of intense cellular activity, including growth and DNA replication, not just a resting phase.

 

Question 10. Why Mitosis is significant?
Answer: Mitosis is significant because it produces identical cells. This process is essential for growth, repair of damaged tissues, and asexual reproduction in many organisms. Mitosis ensures that daughter cells have the exact same genetic information as the parent cell.
In simple words: Mitosis is important because it makes new cells that are exactly the same as the old ones, helping growth and repair.

🎯 Exam Tip: Distinguish mitosis (somatic cell division) from meiosis (gamete formation), remembering their different outcomes for chromosome numbers.

 

Question 11. Why does chromosomal number reduce to half in Meiosis?
Answer: The chromosomal number reduces to half in meiosis because meiosis involves two rounds of cell division after only one round of DNA replication. This reduction is crucial for sexual reproduction, ensuring that when two gametes (sperm and egg) fuse, the resulting zygote has the correct, full set of chromosomes. This halving prevents the chromosome number from doubling in each generation.
In simple words: Meiosis makes the chromosome number half so that when a sperm and egg join, the baby gets the right number of chromosomes.

🎯 Exam Tip: Link the reductional division in meiosis directly to maintaining a constant species chromosome number across generations.

 

Question 13. What are constituents of phloem?
Answer: Phloem is a complex tissue made up of four types of elements:
• Sieve tube,
• Companion cells,
• Phloem fibers (bast fibers), and
• Phloem parenchyma. These components work together to transport sugars and nutrients produced during photosynthesis from leaves to other parts of the plant where they are needed for growth or storage.
In simple words: Phloem is made of sieve tubes, companion cells, phloem fibers, and phloem parenchyma.

🎯 Exam Tip: Remember that phloem transports food (sugars), while xylem transports water and minerals; this is a common point of confusion.

 

Question 14. Name the regions in which parenchyma tissue is present?
Answer: Parenchyma tissue is present in various regions of angiospermic plants. It is found in the cortex and pith of stems and roots, and also in the mesophyll of leaves. This tissue serves multiple functions, including storage, photosynthesis, and secretion, making it a versatile plant tissue.
In simple words: Parenchyma tissue is found in the soft parts of plants like the pith of stems, cortex of roots, and inside leaves.

🎯 Exam Tip: Note that parenchyma cells are usually living and thin-walled, distinguishing them from other plant tissues like sclerenchyma.

 

Question 15. What is the function of meristematic tissue?
Answer: Meristematic tissue functions to produce new cells, which then continue to differentiate and form specialized cells. This tissue is responsible for the growth of the plant, both in length and girth. It contains actively dividing cells that contribute to the plant's development throughout its life.
In simple words: Meristematic tissue makes new cells for plant growth and for forming different types of cells.

🎯 Exam Tip: Recognise meristematic tissue as the "growth tissue" found at growing tips (apical meristem) and sides (lateral meristem) of plants.

 

Question 16. Name any two simple and two complex permanent tissues in plants.
Answer:
Simple permanent tissues: Parenchyma and Collenchyma.
Complex permanent tissues: Xylem and Phloem. Simple tissues are made of one type of cell, while complex tissues are made of multiple cell types working together. Both types contribute to the plant's structural integrity and transport systems.
In simple words: Simple tissues are Parenchyma and Collenchyma. Complex tissues are Xylem and Phloem.

🎯 Exam Tip: Understand that "simple" refers to tissue made of only one cell type, and "complex" refers to tissue made of more than one cell type.

 

Question 17. Name the chief mechanical supporting tissue in plants.
Answer: Collenchyma is the chief mechanical supporting tissue in plants. It provides flexible support to plant organs that are still growing, such as young stems and leaf stalks. Its thick cell walls, especially at the corners, give it strength without limiting growth.
In simple words: Collenchyma is the main tissue that supports plants mechanically.

🎯 Exam Tip: Differentiate collenchyma (flexible support in young parts) from sclerenchyma (hard, rigid support in mature parts).

 

Question 19. Which of the following plant tissues do not possess living protoplasm at maturity?
Answer: Sclerenchyma is the plant tissue that does not possess living protoplasm at maturity. Its cells are dead and have very thick, lignified walls, which provide strength and rigidity to the plant. This tissue is important for structural support in mature plant parts.
In simple words: Sclerenchyma tissue in plants does not have living material inside its cells when it is fully grown.

🎯 Exam Tip: Remember that sclerenchyma's thick, dead cells are crucial for providing maximum mechanical support, like in seed coats and nut shells.

 

Question 20. Name the following:
• Multinucleate muscle fibre
• Spindle-shaped muscle fibre
Answer:
• Multinucleate muscle fibre: Skeletal muscle fibre
• Spindle-shaped muscle fibre: Smooth muscle fibre. These different forms reflect their specific functions and locations within the body, allowing for various types of movement and control.
In simple words: Muscle fibers with many nuclei are skeletal, and spindle-shaped ones are smooth muscle fibers.

🎯 Exam Tip: Associating the shape and number of nuclei with muscle types helps in distinguishing them visually and functionally.

Structure of Living Organisms Short Answer Type Questions

 

Question 1. Why is a cell called the structural and functional unit of life?
Answer: A cell is called the structural and functional unit of life because all living organisms are made of cells, making it the basic building block. Each cell also has the ability to perform all the necessary life functions, such as making new materials, removing waste, using oxygen for energy, and movement. The organelles inside the cell work together to make these functions possible, allowing the cell to live and operate independently. This means life processes are fundamentally organized at the cellular level.
In simple words: A cell is the basic building block of life and can do all the necessary jobs to stay alive, like making energy and removing waste.

🎯 Exam Tip: Highlight both "structural" (building block) and "functional" (performs life processes) aspects in your answer for completeness.

 

Question 2. Why is plasma membrane, called a selectively permeable membrane?
Answer: The plasma membrane is called a selectively permeable membrane because it allows only certain selected molecules to pass through it, while blocking others. This control is crucial for the cell to maintain its internal environment and communicate with its surroundings effectively. It works like a gatekeeper, letting in what is needed and keeping out harmful substances.
In simple words: The plasma membrane lets only some things pass through, so it's called selectively permeable.

🎯 Exam Tip: Explain that this selective nature is essential for cell survival and maintaining homeostasis (stable internal conditions).

 

Question 3. Which organelle is known as the powerhouse of the cell? Why.
Answer: The mitochondrion is known as the powerhouse of the cell. This is because it is where most of the energy needed for various life activities is released, in the form of ATP (adenosine triphosphate) molecules. ATP is like the cell's energy currency, which is then used to power activities such as photosynthesis, protein synthesis, and muscle contraction. Without mitochondria, cells would not have enough energy to function.
In simple words: Mitochondria are called the cell's powerhouse because they make ATP, which is the main energy source for the cell to do its work.

🎯 Exam Tip: Always mention ATP when explaining the "powerhouse" role, as it is the direct energy molecule produced by mitochondria.

 

Question 4. Why do plant cells possess largely sized vacuole?
Answer: Plant cells possess a large-sized vacuole because it plays a vital role in maintaining the cell's water balance and internal pressure. The vacuole also helps in:
(a) Storage- It stores sugars, amino acids, organic acids, salts and some proteins.
(b) Cellular wastes- They are dumped in the vacuole.
(c) Turgidity- The vacuole contains cell sap, which provides turgidity to the cells.
(d) Absorption of water- Vacuole contains an osmotic concentration, required for absorption of water. This large central vacuole is essential for supporting the plant structure and regulating cell growth.
In simple words: Plant cells have a big vacuole to store water, nutrients, and waste, and to keep the cell firm and help absorb water.

🎯 Exam Tip: Connect the large vacuole's function directly to turgor pressure, which is crucial for plant rigidity and upright growth.

 

Question 5. What are viruses? Why do they not show any characteristics of life?
Answer: Viruses are microscopic infectious agents that can only replicate inside the living cells of other organisms. They do not show characteristics of life on their own because, unlike cells, they lack a membrane-bound structure and cellular organelles to perform life functions independently. Viruses are completely inert outside a host cell and only become active when they enter a living body and use its cell machinery to reproduce. This makes them obligate intracellular parasites, existing on the boundary between living and non-living.
In simple words: Viruses don't show life characteristics outside a host because they lack cell parts and can only reproduce by taking over a living cell.

🎯 Exam Tip: Emphasise that viruses are not considered truly "living" because they cannot perform metabolic processes independently.

 

Question 6. Where are chromosomes located? What are they composed of? What is chromatin material and how does it change, just before the cell divides?
Answer: Chromosomes are located inside the nucleus of plant and animal cells. They are primarily composed of DNA (Deoxyribonucleic acid) and proteins, which together form chromatin material. Chromatin material is a tangled mass of thread-like structures found in the nucleus. Just before the cell divides, this chromatin material condenses and organizes itself into distinct, rod-like chromosomes. This packaging ensures that the genetic material can be accurately divided between the two new daughter cells. Chromosomes carry genetic information.
In simple words: Chromosomes are in the nucleus, made of DNA and protein. The tangled chromatin material turns into tight chromosomes before the cell divides.

🎯 Exam Tip: Remember that DNA contains the genetic instructions, and chromatin is the organised form of DNA and proteins within the nucleus.

 

Question 8. What are lysosomes, peroxisomes and centrosomes? Write their functions.
Answer:
Lysosomes: These are small, single-membrane-bound vesicular structures found in the cytoplasm of eukaryotic cells, except for mammalian red blood cells. They contain various enzymes and are formed by the Golgi apparatus.
Functions: Lysosomes are involved in the intracellular digestion of foreign food or microbes and also help in the breakdown of old or damaged cell parts, a process known as autolysis or self-digestion of cells after their death.
Peroxisomes: These organelles are found in photosynthetic plant cells, and in the liver and kidney cells of vertebrates. They contain two types of oxidative enzymes: oxidase and catalase, enclosed by a unit membrane.
Functions: Peroxisomes are involved in the removal of toxic substances through oxidative reactions. In plant cells, they also play a role in photorespiration.
Centrosome: A centrosome is a small microscopic organelle formed of two dark, colored granules called centrioles, surrounded by a transparent cytoplasmic area called centrosphere. It is usually located near the nucleus and is often referred to as the cell center. The centrosome helps in cell division.
In simple words: Lysosomes digest waste, peroxisomes remove toxins, and centrosomes help cells divide. They are all important cell parts.

🎯 Exam Tip: Categorize these organelles by their primary role-lysosomes for digestion, peroxisomes for detoxification, and centrosomes for cell division in animals.

 

Question 9. Explain the structure and functions of Golgi apparatus?
Answer: The Golgi apparatus, also known as the Golgi body or Golgi complex, was first described by Camillo Golgi. It consists of smooth, flattened, membrane-bound sacs called cisternae, which are stacked together in parallel rows. The Golgi apparatus is often surrounded by small, dischargeable vesicles.
Functions:
• It acts as a secretory organelle of the cell.
• It packages materials synthesized in the cell and transports them.
• It is involved in the formation of lysosomes.
• In some cases, complex sugars are made from simple sugars in this organelle. This organelle is like the cell's post office, modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.

In simple words: The Golgi apparatus looks like stacked flattened sacs. It sorts, packages, and sends materials like proteins and lipids around the cell or out of it, and helps make lysosomes.

🎯 Exam Tip: Remember the Golgi apparatus's role in packaging and modification of proteins and lipids, similar to a cellular processing and shipping center.

 

Question 10. Explain cell division?
Answer: Cell division is a fundamental biological process by which a parent cell divides into two or more daughter cells. The German biologist Walter Flemming first observed this process. Cell division is crucial for growth, repair of tissues, and reproduction in living organisms. It ensures the continuity of life by passing genetic material from one generation of cells to the next. This allows a single cell to multiply and form complex organisms.
In simple words: Cell division is when one cell splits into new cells. It's how living things grow, fix themselves, and reproduce.

🎯 Exam Tip: Understand that cell division is essential for all life, driving development from a single cell to a complex organism and maintaining tissue health.

 

Question 11. In which phase, gene exchange between chromatids take place?
Answer: The exchange of genetic material between chromatids, known as crossing over, takes place during Prophase I of meiosis. In the beginning of Prophase I, chromosomes appear as long, thread-like structures with bead-like thickenings. Homologous chromosomes (one from each parent) pair up in a process called synapsis, forming bivalents. During this pairing, non-sister chromatids can exchange segments at points called chiasmata. This exchange creates new combinations of genes, leading to genetic variation in offspring. This process is vital for evolution.
In simple words: Genes are exchanged between chromatids during Prophase I of meiosis, creating new gene combinations.

🎯 Exam Tip: Crossing over in Prophase I is the primary mechanism for genetic recombination, ensuring diversity within a species.

 

Question 12. Describe Meiosis?
Answer: Meiosis is a special type of cell division that occurs during gamete (sex cell) formation, resulting in four daughter cells. Each daughter cell contains half the number of chromosomes compared to the parent cell. This process involves two successive divisions: Meiosis I (reductional division) and Meiosis II (equational division). Meiosis I reduces the chromosomal number by half, producing two haploid cells from a diploid parent cell. Meiosis II then separates the sister chromatids, similar to mitosis, resulting in four haploid cells. This reduction is essential to maintain the species' chromosome number after fertilization. Meiosis ensures genetic diversity through crossing over and independent assortment.
In simple words: Meiosis is a cell division that makes four new cells, each with half the chromosomes of the original cell. This is important for making sperm and egg cells.

🎯 Exam Tip: Remember that meiosis is a two-step process that ultimately produces four genetically unique haploid cells, crucial for sexual reproduction.

 

Question 13. Explain with a diagram, the objective of amitosis in bacteria?
Answer: The objective of amitosis in bacteria is to increase their population rapidly and propagate the species efficiently. In amitosis, the nuclear material, containing a circular chromosome, elongates. A constriction then develops in the middle portion of the chromosome. As this constriction deepens, the circular chromosome divides into two parts. This simple and direct division allows bacteria to multiply quickly under favorable conditions, which is crucial for their survival and colonization. (Note: No diagram was provided in the source for amitosis.)
In simple words: Amitosis helps bacteria multiply fast by simply dividing their nuclear material, leading to many new bacteria quickly.

🎯 Exam Tip: Understand that amitosis is a simpler, more direct form of cell division compared to mitosis or meiosis, often seen in prokaryotes.

 

Question 14. Define Centromere, Centriole, and Charismata?
Answer:
Centromere: A centromere is a constricted region on a chromosome, typically appearing as one or more indentations. It holds the two sister chromatids together and serves as the attachment point for spindle fibers during cell division. The centromere ensures proper segregation of chromosomes.
Centriole: A centriole is a cell organelle found in animal cells. It plays a key role in the formation of the spindle apparatus during nuclear division. Each animal cell usually has a pair of centrioles, which are positioned at right angles to each other.
Charismata: (Correction: The term is 'Chiasmata') Chiasmata are the regions on homologous chromatids where the exchange of genetic material (crossing over) takes place during meiosis. These are visible points of contact between non-sister chromatids where genetic recombination occurs. The formation of chiasmata is critical for increasing genetic diversity.
In simple words: A centromere joins chromosome parts. Centrioles help with cell division in animal cells. Chiasmata are spots where gene parts cross over on chromosomes.

🎯 Exam Tip: Pay attention to the roles of these structures specifically during cell division (mitosis and meiosis), as they are key players in accurate chromosome segregation.

 

Question 15. What are the functions of areolar tissue?
Answer: The main functions of areolar tissue are:
• These tissues fill the empty spaces inside the organs.
• It provides support, elasticity, and strength to the body parts.
• Areolar tissue connects different tissues together, for example, the skin with underlying parts, as well as blood vessels and nerve endings to other body parts.
• It helps in the repair of tissues and healing of wounds.
• It helps in fighting foreign antigens and toxins. This widely distributed tissue acts as a packing material, cushioning organs and facilitating their movement.
In simple words: Areolar tissue fills space, supports organs, connects tissues, helps repair wounds, and fights germs.

🎯 Exam Tip: Remember areolar tissue as a "packaging" tissue that provides both support and flexibility, allowing organs to move slightly without damage.

 

Question 16. How are simple tissues different from complex tissues, in plants?
Answer: Simple tissues in plants are made up of only one type of cells, all of which look similar and perform the same function. Examples include parenchyma, collenchyma, and sclerenchyma. On the other hand, complex tissues are made up of more than one type of cells, which work together to perform a specialized function. Xylem and phloem are examples of complex tissues. Simple tissues primarily offer protection and support, while complex tissues are responsible for conducting water, minerals, and nutrients from roots to leaves and other parts of the plant. This division of labor allows for efficient functioning in plants.
In simple words: Simple tissues have one type of cell, like parenchyma. Complex tissues have many cell types working together, like xylem and phloem.

🎯 Exam Tip: The key difference lies in the number of cell types: one for simple tissues and multiple for complex tissues, each serving specific plant needs.

 

Question 18. How do cardiac muscles resemble both striated and smooth muscle fibres?
Answer: Cardiac muscles show similarities with both striated and smooth muscle fibers. They resemble striated muscles because they are cylindrical in shape, are highly vascular (have rich blood supply), and exhibit alternate dark and light bands. They resemble smooth muscles because their cells are smaller, typically uni-nucleated (have a single nucleus), and are involuntary, meaning their contractions are not under conscious control. This unique blend of features allows the heart to pump blood rhythmically and tirelessly. This combination allows for powerful, rhythmic, and unconscious contractions.
In simple words: Cardiac muscles look like striated muscles (stripes, cylinder shape) but act like smooth muscles (one nucleus, involuntary movement).

🎯 Exam Tip: Focus on the "involuntary" aspect for smooth and cardiac muscles, which is a major functional similarity, while structural similarities vary.

 

Question 19. What are mast cells? What is their function?
Answer: Mast cells are oval-shaped cells found in areolar connective tissue. They contain dense granules within their cytoplasm. These cells secrete several important substances, including heparin and histamine, which are crucial for inflammatory and allergic responses. They also contribute to the matrix of connective tissue. Mast cells act as a first line of defense against pathogens and play a role in wound healing.
In simple words: Mast cells are oval cells in connective tissue that release chemicals like heparin and histamine, important for reactions like allergies and inflammation.

🎯 Exam Tip: Remember that mast cells are key players in allergic reactions and inflammation due to the chemicals they release.

 

Question 20. Describe blood as connective tissue.
Answer: Blood is considered a fluid connective tissue because it connects all parts of the body by transporting substances. Unlike other connective tissues with solid matrices, blood has a fluid matrix called blood plasma, in which various cells move. Blood plasma is a straw-colored, slightly alkaline fluid that contains blood corpuscles (red blood cells, white blood cells) and blood platelets. Blood circulates within vessels, delivering oxygen, nutrients, hormones, and removing waste products. Its unique fluid nature allows it to perform its connective and transport functions throughout the body. It is vital for life as it links every body part.
In simple words: Blood is a fluid connective tissue because it flows everywhere, connecting all body parts and carrying things like oxygen and nutrients in its liquid part called plasma.

🎯 Exam Tip: Emphasise blood's fluid matrix (plasma) and its transport function as key characteristics that classify it as a connective tissue.

Structure of Living Organisms Long Answer Type Questions

 

Question 1. Name the three major functional regions of cells. Briefly mention the component of each and explain the function of each. Draw a labelled diagram of a plant cell.
Answer: All cells, despite varying in shape, size, and activities, have three major functional regions: the plasma membrane, the nucleus, and the cytoplasm. These regions work together to carry out all cellular processes. A plant cell diagram is shown below:

Functions of Plasma Membrane:
• It gives a definite shape to the cell.
• It separates the contents of a cell from its surrounding medium.
• It provides a mechanical barrier for the protection of the internal contents of the cell.
• It is a selectively permeable membrane.
• It regulates the movement of ions, in and out of the cell. The plasma membrane is crucial for maintaining the cell's integrity and regulating its interactions with the environment.

Nucleus: Robert Brown discovered the nucleus in 1831. It is the largest, most prominent organelle in the cell, typically spherical or oval and located centrally. The nucleus controls all cellular activities and carries genetic information.
• Nuclear membrane: This is a double-layered membrane that encloses the nucleus and separates it from the cytoplasm. It contains nuclear pores, which allow the transfer of materials between the nucleus and the cytoplasm. This selective transport is vital for cell function.
• Nucleoplasm: This is a thick, jelly-like semi-fluid found inside the nucleus. It contains chromatin material and nucleolus suspended within it. The nucleoplasm provides a medium for nuclear activities.
• Chromatin material: It consists of a long, coiled network of thread-like structures made of deoxyribonucleic acid (DNA). DNA is responsible for storing and transmitting hereditary information from one generation to the next. Before cell division, chromatin condenses into compact rod-like chromosomes.
• Nucleolus: This is a more or less round structure found inside the nucleus. It contains RNA (ribonucleic acid) and proteins, which are important for protein synthesis in the cytoplasm. The nucleolus plays a key role in ribosome formation.
Functions of Nucleus:
• The nucleus controls all the metabolic activities of the cell through its DNA molecules.
• It regulates the cell cycle.
• It is concerned with the transmission of hereditary traits from the parent to offsprings.
• The main function of the nuclear reticulum is participation in cell-division.
• Genes are located in a linear fashion in chromosomes. Genes control and carry hereditary characters from one generation to another.
• Nucleolus assists in protein synthesis. Formation of ribosomes takes place in the nucleolus.
Cytoplasm: It is the fluid content of the cell, located between the plasma membrane and the nuclear envelope. It contains various cell organelles, each performing different functions. Many metabolic reactions occur here.
In simple words: Cells have three main parts: the plasma membrane (outer boundary), the nucleus (control center with DNA), and the cytoplasm (jelly-like fluid with organelles). Each part has specific jobs to keep the cell working, and the plant cell diagram shows these parts.

🎯 Exam Tip: When describing cell parts, always mention both structure and function. For the plant cell diagram, ensure all key organelles like cell wall, chloroplast, and vacuole are clearly labeled.

 

Question 2. Draw a labelled diagram of an animal cell. Describe the structure and give the name of four cell organelles.
Answer: An animal cell diagram is shown below:

(1) Mitochondria: These are small, rod-shaped organelles. Each mitochondrion is surrounded by a double membrane. The outer membrane is smooth, while the inner membrane forms numerous finger-like folds called cristae, which project into the internal matrix. The matrix is filled with semi-liquid fluid and contains many enzymes that control and regulate energy release during food molecule oxidation in respiration. This organelle is the site of respiration and is often called the "powerhouse" of the cell because it generates energy in the form of ATP. This energy is essential for various cellular activities.

(2) Ribosomes: Ribosomes are small, dense, rounded, and granular particles made of RNA and proteins. They can be found either free in the cytoplasm or attached to the membrane of the endoplasmic reticulum. Their main function is to synthesize proteins. Ribosomes are crucial for translating genetic information into functional protein molecules, which are vital for all cellular processes.

(3) Lysosomes: Lysosomes are spherical, sac-like structures, each bounded by a single membrane. They are filled with dense liquid containing various enzymes that help in the digestion of food molecules. Lysosomes control the digestion of cells, help digest dead cells and disintegrate cells. They are more numerous in white blood corpuscles, allowing them to digest microbes and bacteria effectively. They are often called the "suicide bags" of the cell.

(4) Endoplasmic reticulum: The endoplasmic reticulum (ER) is an irregular network of interconnected channels, visible only with an electron microscope. These organelles are present in eukaryotic cells but absent in prokaryotic cells and mammalian red blood cells. The ER is of two types:
• Smooth endoplasmic reticulum: This type lacks ribosomes on its outer surface. It is mainly found in cells that synthesize and store carbohydrates, fats, steroid hormones, and other non-protein products.
• Rough endoplasmic reticulum: This type has ribosomes firmly attached to its outer surface. The rough ER is involved in protein synthesis and modification. The ER acts as a transport system and helps in membrane biogenesis.
In simple words: An animal cell has a nucleus, mitochondria (for energy), ribosomes (for proteins), lysosomes (for waste), and an endoplasmic reticulum (for making and moving things). These parts work together for the cell to live and grow.

🎯 Exam Tip: For diagrams, ensure clear labels and appropriate magnification. When describing organelles, always include their key structural features and primary functions.

 

Question. Give briefly the difference between plant and animal cell
Answer:

The fundamental differences reflect their distinct lifestyles and functional requirements, such as photosynthesis in plants and motility in animals.
In simple words: Plant cells have a strong cell wall, big vacuoles, and chloroplasts (for food), while animal cells don't have a cell wall or chloroplasts, have small vacuoles, and are flexible.

🎯 Exam Tip: When comparing, always highlight key structural differences like the cell wall, chloroplasts, and vacuole size, as these are primary distinctions between plant and animal cells.

 

Question 4. Describe meiosis. Draw labelled diagram of any two phases.
Answer: Meiosis is a specific type of cell division vital for sexual reproduction. During meiosis, a cell undergoes two divisions, resulting in four daughter cells, each with half the number of chromosomes of the parent cell. This reduction is crucial because when gametes (sperm and egg) fuse during fertilization, the original number of chromosomes is restored in the zygote. If the chromosome number didn't halve, each generation would have double the chromosomes, which is not sustainable. The first meiotic division (Meiosis I) reduces the chromosome count, while the second (Meiosis II) is similar to mitosis, maintaining the halved number. The whole process ensures genetic variation in offspring.

🎯 Exam Tip: Remember to clearly label each part of your diagram, especially the chromosomes, poles, and the cell boundaries, for full marks.

 

Question 5. Meiosis in tabular form?
Answer: Meiosis is a cell division process that creates gametes (sperm and egg cells) with half the usual number of chromosomes. It involves two main divisions. The table below compares the key features of Meiosis I and Meiosis II, highlighting how genetic material is shuffled and reduced over two stages. It is crucial for sexual reproduction and maintaining the correct chromosome number across generations.

In simple words: Meiosis I halves the chromosome number and mixes up genes, while Meiosis II then separates the chromatids, making four unique cells, each with half the original chromosomes.

🎯 Exam Tip: When comparing Meiosis I and Meiosis II, focus on the key differences like chromosome number reduction, genetic exchange, and what separates in each stage.

 

Question 6. Compare and contrast the different types of animal tissues
Answer: Animal tissues are groups of cells that work together to perform specific functions. There are four main types: Epithelial, Connective, Muscular, and Nervous. Each type has a unique structure suited to its role, allowing for the complex organization and functioning of an animal body. Understanding these differences is key to knowing how different body parts are built and what they do.

In simple words: Animal tissues are like building blocks; epithelial tissues cover and line, connective tissues hold things together, muscular tissues help us move, and nervous tissues send messages throughout the body.

🎯 Exam Tip: When comparing tissues, focus on how their structure (cell arrangement, matrix) directly relates to their function in the body. This will help you distinguish between them.

 

Question 7. In brief, state what happens when.
(a) Dry apricots are left for some time in pure water and later transferred to the sugar solution.
(b) A red blood cell is kept in concentrated saline solution?
(c) Rheo leaves are boiled in water first and then a drop of sugar syrup is put on it?
(d) The plasma -membrane of a cell breaks down?
(e) Golgi apparatus is removed from the cell?
Answer:
(a) When dry apricots are put in pure water, they absorb water and swell up due to a process called endosmosis (water moving into the cell). After this, if they are moved to a concentrated sugar solution, they will lose water and shrink due to exosmosis (water moving out of the cell). This shows how cells react to different water concentrations around them.
(b) If a red blood cell is placed in a concentrated saline solution, it will lose water due to exosmosis. This causes the cell to shrink because the water inside moves out to balance the higher salt concentration outside. The cell becomes shrivelled, which is not good for its function.
(c) If Rheo leaves are boiled, their cells, especially the plasma membrane, are killed. When sugar syrup is then applied, plasmolysis (shrinking of the protoplasm) will not happen. This is because only living cells can perform osmosis and absorb or lose water; dead cells cannot. The cell membrane must be alive and intact for osmosis to occur.
(d) If the plasma membrane of a cell breaks down, the cell will not be able to control what goes in and out. This means it will lose its internal contents and cannot maintain its shape or function, leading to the cell's death. The plasma membrane is essential for keeping the cell alive and organized.
(e) If the Golgi apparatus is removed from a cell, several vital processes will stop. The cell won't be able to package and transport proteins and lipids, which are made in other parts of the cell. It also won't be able to form new membranes or lysosomes. This means the cell would struggle to send materials to the right places, process waste, or protect itself, eventually leading to its dysfunction.
In simple words: If you put dry apricots in water, they swell, but in sugar water, they shrink. Red blood cells shrink in salty water. Boiling Rheo leaves kills them, so they won't react to sugar syrup. If a cell's skin (plasma membrane) breaks, it dies. If the cell's packaging system (Golgi apparatus) is removed, it can't send things where they need to go and would stop working properly.

🎯 Exam Tip: For "what happens when" questions, identify the core biological process (like osmosis, cell death, or organelle function) affected by the change and explain the consequence clearly.