CBSE Class 9 Biology Fundamental Unit Of Life Worksheet Set A

Very Short Answer Type Question :

Exam Questions NCERT Class 9 Science Chapter 5 The Fundamental Unit of Life

Question. Who gave the cell theory? What does it state? Which organism is an exception of cell theory?
Answer : Two biologists; “Schleiden and Schwann” gave the “Cell theory” which expanded by “Rudolf Virchow”.Cell theory states that :
(i) All plants and animals are composed of cells.
(ii) Cell is the basic unit of life.
(iii) All cells arise from pre-existing cells. Viruses are the exceptions of cell theory.

Question. Do vacuoles store material? If so, name them.
Answer :Yes, vacuoles store some important substances required in life of the plant cell. These are amino acids, sugars, various organic acids and also some proteins.
Example : Amoeba, vacuoles also store food.

Question. How do substances like CO2 and water move in and out of the cell?
Answer : The substances like CO2 move in and out of a cell by diffusion from the region of high concentration to low concentration. Water also obey the law of diffusion.
The movement of water molecule through such a selective permeable membrane is called osmosis.

Question. How does fungi and bacteria can withstand much greater changes in the surrounding medium than animal cells?
Answer : The cell wall present in fungi and bacteria permits these cells to resist very dilute external medium without bursting. Water is taken up by osmosis.
Hence, cells swell and build the pressure against the cell wall. The wall exerts an equal pressure against the swollen cell. It is because of the cell wall, such cells can resist much greater changes in the surrounding medium than animal cells.

Question. Give difference between diffusion and osmosis.
Answer : Diffusion :
1. Diffusion can occur in any medium.
2. The diffusing molecules may be solids, liquids or gases.
3. Semipermeable membrane is not required.
4. An equilibrium in the free energy of diffusion molecules is achieved in the system.
Osmosis :
1. It occurs only in liquid medium.
2. It involves movement of solvent molecules only.
3. Semipermeable membrane is required.
4. Equilibrium in the free energy of solvent molecules is never achieved.

Question. What are the function of endoplasmic reticulum and lysosome.
Answer : (a) Functions of endoplasmic reticulum :
(i) It forms supporting skeletal framework of the cell.
(ii) ER provides a pathway for the distribution of nuclear material from one cell to the other.
(b) Functions of lysosomes :
(i) Lysosomes serve as intracellular digestive system. They destroy any foreign material which enters the cells such as bacteria and virus.
(ii) Lysosomes also remove the worn out and poorly working cellular organelles by digesting them to make way for their new replacements.

Question. Explain the functions of various cell organelles.
Answer : Functions of cell organelles :
(i) Endoplasmic Reticulum : It forms the supporting skeletal framework of the cell.
(ii) Ribosomes : It synthesises proteins.
(iii) Golgi Apparatus : It produces vacuoles which contain cellular secretion.
(iv) Lysosomes : It serves as intracellular digestive system as it digest the foreign materials which enter the cell.
(v) Mitochondria : These are the sites of cellular respirations.
(vi) Plastids : These are present only in plants and trap solar energy to manufacture food for plants.
(vii) Vacuoles : They help to maintain the osmotic pressure in a cell.
(viii) Peroxisomes : They carry-out some oxidative reactions.
(ix) Centrosome : It helps in cell division in the animal cell.

Question. Which cell organelle is known as the ‘suicidal bags’ of a cell? Why?
Answer :Lysosomes are known as suicidal bag of cell. During the disturbance in cellular metabolism, lysosome may burst and the enzymes digest their own cell. Hence, lysosome are called ‘suicide bags’ of a cell.

Question. What is nucleoid?
Answer : The nuclear region in some cells are poorly defined due to the absence of a nuclear membrane, it contains only nucleic acid. This undefined nuclear region with nucleic acid in it is called nucleoid.

Question. (i) Name the largest animal cell.
(ii) Name the smallest cell.
Answer : (i) An ostrich egg.
(ii) Pleuro pneumonia bacterium.

Question. What is osmosis?
Answer : The movement of water molecules through a selectively permeable membrane is called osmosis. This takes place from higher water concentration to lower water concentration.

Question. Name the cleaning organelle in the cell.
Ans : Lysosomes.

Question. What is the full form of DNA?
Ans : DNA (Deoxyribose Nucleic Acid).

Question. Name the cell organelle which helps in the formation of lysosome.
Ans : Golgi apparatus.

Question. Why are plasma membrane called selectively permeable membrane?
Ans : Plasma membrane allows to go in and out some materials to and from the cell. It also prevents movement of some other materials. So, it is called selectively permeable membrane.

Question. What are ribosomes? Where are ribosomes located in the cell? What is their function?
Ans : Ribosomes are spherical organelles present in the cell which are either freely distributed in the cytoplasm or may be attached to the endoplasmic reticulum. It has ribosomal RNA (Ribonucleic acid) and proteins. It helps in protein synthesis.

Question. What is a eukaryotic cell?
Ans : Eukaryotic cells are much larger and more complex than prokaryotic cells. Their complexity is reflected in their DNA content. These cells contain a membrane bound nucleus containing nucleolus. A eukaryotic cell contains many membrane bound cell organelles like the mitochondria, the endoplasmic reticulum and the Golgi bodies. These cells have more than one chromosome and the cell division is by meiotic mode.

Question. Explain the structure and function of Golgi bodies.
Ans : Structures : Golgi bodies consist of a system of membrane-bound vesicles arranged in stacks parallel to each other called cisterns. These membranes have connections with the membrane of endoplasmic reticulum (ER).
Functions :
(i) The material synthesized near the ER is packaged and dispatched to various targets inside and outside the cell through Golgi apparatus.
(ii) It also stores, modifies and helps in the packaging of products in vesicles.
(iii) In some cases, complex sugars may be made from simple sugars in it.
(iv) It also helps in the formation of lysosomes.

Question. What are the types of cell on the basis of type oforganization? 
Ans : (i) Prokaryotic cells : Cells which have less developed nucleus and without nuclear membrane and nucleolus. These are primitive and incomplete cells. E.g. bacteria.
(ii) Eukaryotic cells : Cells which have well developednucleus with nuclear membrane and nucleolus. E.g. plants and animals.

Question. What is lacking in a virus which makes it dependant on a living cell to multiply?
Ans : Viruses look selectively permeable process membrane and cell organelles. Thus, they lack a basic structural organization to perform various life processes effectively and in their own way. After entering in a living cell, a virus utilizes its own genetic material and machinery of host cell to multiply.

Question. What would happen if when we put an animal cell into a solution of sugar or salt in water?
Ans : The following three things could happen : (i) If the solution surrounding the cell is very dilute than cytoplasm, the water will move into the cell, i.e., the cell will gain water.
(ii) If the solution has exactly similar water concentration as that of cytoplasm of cell, there will be no net movement of water across the cell membrane, i.e., no gain or loss of water from the cell.
(iii) If the medium (solution) has a lower concentration of water than the cell, i.e., the solution is concentrated, the cell will lose water by osmosis. How do all cells look alike in terms of shape and size?
Ans : Cells vary in shapes and sizes according to the fusion. Generally, cells are spherical but they may be long and branched as in nerve cell, Kidney shaped as guard cell in plant’s leaves, discoid as RBC, spindle shaped as muscle cell, etc. Size of cell varies from 0.2 mm to 18 cm in diameter. Some are microscopic while some are visible with naked eyes.
For example :
(i) Size of a typical cell in a multicellular organism ranges from 20-30 mn.
(ii) The largest cell is ostrich egg (15 cm in diameter with shell and 8 cm in diameter without shell).
(iii) The longest cell is nerve cell (up to 1 m. or more) and red blood cells are the smallest cell in our body.
(iv) Smallest cells so far known are PPLOs, e.g. mycoplasma (0.1 mm in diameter).

Question. Who gave the cell theory? What does it state? Which organism is an exception of cell theory?
Ans : Two biologists; “Schleiden and Schwann” gave the “Cell theory” which expanded by “Rudolf Virchow”.Cell theory states that :
(i) All plants and animals are composed of cells.
(ii) Cell is the basic unit of life.
(iii) All cells arise from pre-existing cells. Viruses are the exceptions of cell theory.

Question. Do vacuoles store material? If so, name them.
Ans : Yes, vacuoles store some important substances required in life of the plant cell. These are amino acids, sugars, various organic acids and also some proteins.
Example : Amoeba, vacuoles also store food.

Question. How do substances like CO2 and water move in and out of the cell?
Ans : The substances like CO2 move in and out of a cell by diffusion from the region of high concentration to low concentration. Water also obey the law of diffusion.
The movement of water molecule through such a selective permeable membrane is called osmosis.

Question. How does fungi and bacteria can withstand much greater changes in the surrounding medium than animal cells?
Ans : The cell wall present in fungi and bacteria permits these cells to resist very dilute external medium without bursting. Water is taken up by osmosis.
Hence, cells swell and build the pressure against the cell wall. The wall exerts an equal pressure against the swollen cell. It is because of the cell wall, such cells can resist much greater changes in the surrounding medium than animal cells.

Question. Give difference between diffusion and osmosis.
Ans :
Diffusion :
1. Diffusion can occur in any medium.
2. The diffusing molecules may be solids, liquids or gases.
3. Semipermeable membrane is not required.
4. An equilibrium in the free energy of diffusion molecules is achieved in the system.
Osmosis :
1. It occurs only in liquid medium.
2. It involves movement of solvent molecules only.
3. Semipermeable membrane is required.
4. Equilibrium in the free energy of solvent molecules is never achieved.

Question. What are the function of endoplasmic reticulum and lysosome.
Ans :
(a) Functions of endoplasmic reticulum :
(i) It forms supporting skeletal framework of the cell.
(ii) ER provides a pathway for the distribution of nuclear material from one cell to the other.
(b) Functions of lysosomes :
(i) Lysosomes serve as intracellular digestive system. They destroy any foreign material which enters the cells such as bacteria and virus.
(ii) Lysosomes also remove the worn out and poorly working cellular organelles by digesting them to make way for their new replacements.

Question. Explain the functions of various cell organelles.
Ans : Functions of cell organelles :
(i) Endoplasmic Reticulum : It forms the supporting skeletal framework of the cell.
(ii) Ribosomes : It synthesises proteins.
(iii) Golgi Apparatus : It produces vacuoles which contain cellular secretion.
(iv) Lysosomes : It serves as intracellular digestive system as it digest the foreign materials which enter the cell.
(v) Mitochondria : These are the sites of cellular respirations.
(vi) Plastids : These are present only in plants and trap solar energy to manufacture food for plants.
(vii) Vacuoles : They help to maintain the osmotic pressure in a cell.
(viii) Peroxisomes : They carry-out some oxidative reactions.
(ix) Centrosome : It helps in cell division in the animal cell.

Question. Which cell organelle is known as the ‘suicidal bags’ of a cell? Why?
Ans : Lysosomes are known as suicidal bag of cell. During the disturbance in cellular metabolism, lysosome may burst and the enzymes digest their own cell. Hence, lysosome are called ‘suicide bags’ of a cell.

Question. What is nucleoid?
Ans : The nuclear region in some cells are poorly defined due to the absence of a nuclear membrane, it contains only nucleic acid. This undefined nuclear region with nucleic acid in it is called nucleoid.

Question. (i) Name the largest animal cell.
(ii) Name the smallest cell.
Ans : (i) An ostrich egg.
(ii) Pleuro pneumonia bacterium.

Question. What is osmosis?
Ans : The movement of water molecules through a selectively permeable membrane is called osmosis. This takes place from higher water concentration to lower water concentration.

Question. Explain the following terms :
(a) Plasma membrane,
(b) Cytoplasm,
(c) Nucleus.
Ans : (a) Plasma membrane : It is a thin membrane which controls the passage of materials in and out of the cell. It is also called selectively permeable membrane. It makes the outer oundary of the cell and is made up of protein.
(b) Cytoplasm : It is transparent jelly-like thick substance present in the cell. It makes the ground of the cell in which all the cell organelles are suspended.
(c) Nucleus : It is a double-layered membrane structure which contains chromosomes required for the inheritance of characteristics from one generation to the other.

Question. What is lacking in a virus which makes it dependant on a living cell to multiply?
Ans : Viruses do not have a basic structural organization to perform various life processes in their own as they look selectively permeable process membrane. After
entering in a living cell, a virus utilizes its own genetic material and machinery of host cell to multiply.

Question. Expand the term ATP. What is use of ATP?
Ans : ATP stands for Adenosine Tri-phosphate Application : ATP molecules are rich in chemical energy. The body cells use this energy for synthesis of new chemical compounds, and for mechanical work done by cells.

Question. What is the function of nucleus in a cell?
Ans : The nucleus plays a very important role in the reproduction of cells. It also helps the single cell to divide and form two new daughter cells. It also helps in an important role in determining how cell will develop.

Question. Name various cell organelles.
Ans : The cell organelles are : Endoplasmic Reticulum, Ribosomes, Golgi apparatus, Lysosomes, Mitochondria, Plastids, Vacuoles, Peroxisomes and Centrosome.

Question. (a) Name the organelle which provides turgidity and rigidity to the plant cell. Name any two substances which are present in it.
(b) How are they useful in unicellular organisms?
Ans : (a) Plant cells have big vacuoles that provide them turgidity and rigidity. Plant vacuoles store amino acids, sugars, various organic acids and some proteins.
(b) In unicellular organism they can serve the following works :
(i) Forming food vacuoles : In single celled organisms like amoeba, the food vacuole contains the food items that the amoeba has engulfed. After that the food items are digested by the enzymes.
(ii) Removal of excess water and wastes : In some unicellular organisms, vacuoles play important roles in egesting excess water and some wastes from the cell.

Question. What is membrane biogenesis?
Ans : The endoplasmic reticulum helps in the manufacture of proteins and fat molecules or lipids which are important for the cell function. These proteins and lipids helps in the building of the cell membrane. This process is known as membrane biogenesis.

Question. All cells come from pre-existing cells. Justify?
Ans : All organisms around are made up of one or more cells. There are single cells organism called unicellular like amoeba whereas some single body are made up of many cells called multicellular organism. Cells divide to produce cells of their own kind. Hence, all cells come from pre-existing cells.

Question. What are chromosomes? What are they made of?
Ans : The compact rod-like bodies inside the nucleus are called chromosomes. These are seen at the time of cell division. They are made up of deoxyribonucleic acid or DNA and proteins.

Question. What is the cell wall composed of ?
Ans : The cell wall is composed of cellulose.

Question. Name two cells with cell wall.
Ans : Onion cell (plant cell) and fungi are two cells with cell wall.

Question. Which organelle makes the digestive enzyme of lysosome?
Ans : Rough endoplasmic reticulum makes the digestive enzyme of lysosomes.

Question. Name the cell organelle which helps in the transporta tion of material.
Ans : Endoplasmic reticulum.

Question. Name the smallest cell and the longest cell in human body.
Ans : The smallest cell is the red blood cell or sperm cell in male. The longest cell is the nerve cell.

in and out of the cell.