GSEB Class 9 Science Solutions Chapter 5 The Fundamental Unit of Life

In-Text Activities Solved

Activity 5.1
Answer:
(a) The onion skin is utilized as a thin piece to view the cells of an onion.
In simple words: The outer layer of an onion is used as a thin slice to see its cells.
(b) We notice many tightly packed units called cells that are neatly arranged. We can sketch the structures observed through the microscope onto an observation sheet. Yes, it resembles the diagram shown below.
In simple words: We see lots of cells packed closely together. We can draw what we see under the microscope, and it looks like the picture provided.

Exam Tip: When describing observations, ensure to mention the arrangement and typical appearance of the cells, and always refer to any provided diagrams.

Activity 5.2
Answer:
(a) Yes, all cells appear similar in their form and dimensions.
In simple words: Yes, all cells look quite alike in how they are shaped and how big they are.
(b) Yes, all cells share a similar structure.
In simple words: Yes, all cells have a similar internal layout.
(c) Yes, cells from various parts of a plant vary because cell type is determined by the task they carry out.
In simple words: Yes, plant cells differ depending on where they are and what job they do.
(d) The cell membrane, cell wall, cytoplasm, and nucleus are found in every cell.
In simple words: All cells contain a cell membrane, cell wall, cytoplasm, and a nucleus.

Exam Tip: Remember that while basic components are common, cell shape and size can adapt to specific functions within an organism.

Activity 5.3
Answer:
(a) The egg expands because water moves into it via osmosis (since the liquid inside the egg has a higher concentration).
In simple words: The egg gets bigger because water goes inside it through osmosis, as the liquid inside the egg is stronger.
(b) Water exits the egg mixture and moves into the salt mixture because the salt mixture is more concentrated (meaning the fluid outside the egg holds a higher concentration).
In simple words: Water leaves the egg and goes into the salt solution because the salt solution is stronger, meaning more concentrated.

Exam Tip: Always remember that water moves from an area of higher water concentration to an area of lower water concentration across a semi-permeable membrane.

Activity 5.4
Answer:
(a) Reason. Raisins or apricots get bigger as water enters them from outside because the water amount is lower inside the cell compared to the outer solution. So, water flows into the cell through endosmosis.
In simple words: Raisins or apricots swell up because water goes inside them from outside. This happens because there is less water inside the cells than in the outer solution, so water moves in by endosmosis.
(b) Reason. Raisins or apricots get smaller as water leaves them because the water level is higher inside the cell compared to the outer solution. Therefore, water moves out of the cell by exosmosis.
In simple words: Raisins or apricots shrink because water moves out of them. This is because there is more water inside their cells than outside, so water exits by exosmosis.

Exam Tip: Differentiate clearly between endosmosis (water entering) and exosmosis (water leaving) based on the concentration gradient.

Activity 5.5
Answer: A regular compound microscope utilizes light to show a larger picture of an object. Electron microscopes employ electrons to provide a highly magnified image of the object, offering greater detail than a compound microscope.
In simple words: A normal microscope uses light to make things look bigger. An electron microscope uses electrons to make things look much bigger and shows more details than a regular microscope.

Exam Tip: When comparing microscopes, highlight the key difference in their illumination source (light vs. electrons) and the resulting magnification and resolving power.

Activity 5.6
Answer:
(a) We notice the cell experiences plasmolysis, which is the shrinking of its protoplasm. This happens when water moves out of the cell because a more concentrated solution is present outside.
In simple words: The cell shrinks due to plasmolysis because its inside material pulls away. This happens when water leaves the cell because the liquid outside is stronger.
(b) No impact from a strong sugar or salt solution will be visible if the leaves are boiled for a few minutes. Plasmolysis will not happen because the cells die in boiling water. This shows that only living cells experience protoplasm shrinking or swelling as water moves in or out. This process does not occur after boiling leaves, as the plasma membrane loses its selective permeability.
In simple words: Boiling leaves means a strong sugar or salt solution won't affect them. Plasmolysis doesn't happen because the cells are dead. This proves only living cells change size when water moves, as boiled leaves lose their cell membrane's special ability.

Exam Tip: Remember that plasmolysis is a phenomenon specific to living cells because it depends on the integrity and selective permeability of the plasma membrane.

Activity 5.7
Answer:
(a) We see the cheek cells. Their shape is flat, polygonal, and has uneven edges. The picture of cheek cells is displayed below:
In simple words: We look at cheek cells. They are flat, many-sided, and have rough borders. A drawing of them is shown.
(b) Indeed, a dark, round or oval dot-like part called the nucleus is found near the middle of each cheek cell. Similar structures are also visible in onion cells, but not in the middle, because a big central vacuole fills the center of an onion cell, and the nucleus is located at its edge.
In simple words: Yes, a dark, round nucleus is in the center of each cheek cell. Onion cells also have a nucleus, but it's on the side because a large empty space (vacuole) takes up the middle.

Exam Tip: When observing cells, identify the nucleus, cytoplasm, and cell boundary. Note differences in nuclear position (central vs. peripheral) and cell shape across different cell types.

Gujarat Board Class 9 Science The Fundamental Unit of Life Textbook Questions and Answers

Question 1. Make a comparison and write down ways in which plant cells are different from animal cells.
Answer:
Plant Cell:

• A cell wall is present.
• Plastids are present.
• A large central vacuole is present.
• Centrioles are absent.

• A cell wall is absent.
• Plastids are absent.
• Vacuoles are either absent or are very small.
• Centrioles are present.

Exam Tip: Clearly list distinguishing features for both plant and animal cells, focusing on the presence or absence of key organelles like the cell wall, plastids, and a large central vacuole.

Question 2. How is a prokaryotic cell different from a eukaryotic cell?
Answer:
Prokaryotes:

• These organisms' cells do not have a clearly defined nuclear membrane.
• They do not have membrane-bound cell organelles.
• Their size is generally small (1-10 pm).
• They possess a single chromosome.

• These organisms' cells have a clearly defined nuclear membrane.
• They have membrane-bound cell organelles.
• Their size is generally large (5-100 pm).
• They have more than one chromosome.

Exam Tip: When comparing prokaryotic and eukaryotic cells, highlight the presence or absence of a true nucleus, membrane-bound organelles, and differences in size and chromosome number.

Question 3. What would happen if the plasma membrane ruptures or breaks down?
Answer: The plasma membrane controls the movement of materials both into and out of the cell. Thus, if this membrane breaks or tears, the control over substances would be impacted. The cell's contents would leak out, and the cell would eventually die.
In simple words: If the plasma membrane breaks, the cell can no longer control what goes in and out. The cell's insides would spill out, and the cell would die.

Exam Tip: Emphasize the plasma membrane's role in selective permeability and maintaining cell integrity; its rupture leads to loss of control and cell death.

Question 4. What would happen to the life of a cell if there was no Golgi apparatus?
Answer: If there was no Golgi apparatus, then the following processes carried out by it would get affected:

• The storage, modification, and packaging of products in vesicles.
• The packaging and dispatch of the material synthesized near the ER to various targets inside and outside the cell.
• The formation of lysosomes.
• The creation of the cell plate during cell division.

Exam Tip: Focus on the Golgi apparatus's functions in processing, packaging, and transporting materials, as well as its role in lysosome and cell plate formation.

Question 5. Which organelle is known as the powerhouse of the cell? Why?
Answer: Mitochondria are known as the cell's powerhouse because they store the energy produced by cells during breathing. Energy is kept in mitochondria as adenosine triphosphate (ATP), which is released when the cell requires it.
In simple words: Mitochondria are called the cell's powerhouses because they hold the energy made during cell breathing. This energy is stored as ATP and used when the cell needs power.

Exam Tip: Always associate mitochondria with energy production and storage (ATP) through cellular respiration, explaining why it earns the "powerhouse" title.

Question 6. Where do the lipids and proteins constituting the cell membrane synthesised?
Answer: The lipids that form the cell membrane are created by the smooth endoplasmic reticulum (SER). The proteins are made by ribosomes, which are connected to the rough endoplasmic reticulum (RER).
In simple words: The smooth ER makes cell membrane lipids, while ribosomes attached to the rough ER make the proteins for the cell membrane.

Exam Tip: Distinguish between the roles of SER (lipid synthesis) and RER (protein synthesis, via ribosomes) in forming the cell membrane components.

Question 7. How does Amoeba obtain its food?
Answer: The Amoeba consumes food using finger-like extensions called pseudopodia through a process known as endocytosis. Pseudopodia assist in surrounding the food, which then gets enclosed in a food vacuole. Inside this food vacuole, the complex food bits are broken into simpler materials and spread into the Amoeba's cytoplasm. Any leftover undigested food is expelled from the cell by exocytosis.
In simple words: Amoeba eats by using its fake feet, called pseudopodia, to grab food through a process called endocytosis. The food goes into a food bubble, gets broken down, and then spreads into the cell. Waste food is pushed out by exocytosis.

Exam Tip: When explaining Amoeba feeding, use the key terms "pseudopodia," "endocytosis" (for engulfment), "food vacuole" (for digestion), and "exocytosis" (for waste removal).

Question 8. What is osmosis?
Answer: Osmosis is the process where water moves from an area of high water concentration to an area of low water concentration, passing through a semi-permeable membrane.
In simple words: Osmosis is when water flows from a place with lots of water to a place with less water, going through a special skin (membrane).

Exam Tip: Define osmosis precisely, including the movement of water, the concentration gradient, and the role of a semi-permeable membrane.

Question 9. Carry out the following osmosis experiment:
Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water.
Now,
(a) Keep cup A empty
(b) Put one teaspoon sugar in cup B
(c) Put one teaspoon salt in cup C
(d) Put one teaspoon sugar in the boiled potato cup D.
Keep these for two hours. Then observe the four potato cups and answer the following:
(i) Explain why water gathers in the hollowed portion of B and C.
(ii) Why is potato A necessary for this experiment?
(iii) Explain why water does not gather in the hollowed out portions of A and D.
Answer:
(i) Water collects in the empty part of cups B and C because the water level is higher in the trough than in the hollow sections of B and C. The potato cells' plasma membrane functions as a semi-permeable membrane, letting water move in through osmosis.
In simple words: Water fills cups B and C because there's more water in the outer tray than in the cups. The potato skin acts like a filter, letting water enter by osmosis.
(ii) Potato A serves as a control for the experiment, allowing us to understand the changes that happen during the test.
In simple words: Potato A is a comparison cup in the experiment. It helps us see what changes actually occurred during the test.
(iii) Water does not collect in cup A because it is unfilled, so osmosis cannot happen. In cup D, the cell membrane's semi-permeable property is lost after boiling, preventing the process of osmosis.
In simple words: Water doesn't gather in cup A because it's empty, so osmosis doesn't occur. In cup D, boiling made the cell membrane lose its special filtering ability, so osmosis also doesn't happen.

Exam Tip: For experiment-based questions, describe observations, link them to scientific principles (like osmosis and semi-permeability), and explain the role of controls in validating results.