Exercise – Chapter 5: The Fundamental Unit of Life
Question 1
Make a comparison and write down ways in which plant cells are different from animal cells.
Answer:
| Feature | Plant Cell | Animal Cell |
|---|---|---|
| Cell wall | Present | Absent |
| Plastids |
Present (chloroplasts, etc.) |
Absent |
| Vacuole | Large central vacuole | Small or absent |
| Shape |
Usually regular (rectangular) |
Usually irregular (rounded) |
| Mode of nutrition | Autotrophic | Heterotrophic |
Question 2
How is a prokaryotic cell different from a eukaryotic cell?
Answer:
| Prokaryotic Cell | Eukaryotic Cell |
|---|---|
| No true nucleus | True nucleus present |
| Nuclear membrane absent |
Nuclear membrane present |
| Single chromosome | More than one chromosome |
| Membrane-bound organelles absent |
Membrane-bound organelles present |
| Smaller in size | Larger in size |
Question 3
What would happen if the plasma membrane ruptures or breaks down?
Answer:
If the plasma membrane ruptures, the cell contents will leak out, and the entry and exit of substances cannot be controlled.
As a result, the cell will die.
Question 4
What would happen to the life of a cell if there was no Golgi apparatus?
Answer:
If the Golgi apparatus is absent:
-
Proteins and lipids will not be modified, packaged, or transported
-
Secretion from the cell will stop
As a result, the cell will not function properly and may die.
Question 5
Which organelle is known as the powerhouse of the cell? Why?
Answer:
Mitochondria are known as the powerhouse of the cell because they produce energy in the form of ATP, which is required for all cellular activities.
Question 6
Where do the lipids and proteins constituting the cell membrane get synthesised?
Answer:
-
Proteins are synthesised on ribosomes of rough endoplasmic reticulum (RER)
-
Lipids are synthesised in the smooth endoplasmic reticulum (SER)
Question 7
How does an Amoeba obtain its food?
Answer:
Amoeba obtains its food by endocytosis.
It surrounds the food particle with pseudopodia, forming a food vacuole, where digestion takes place.
Question 8
What is osmosis?
Answer:
Osmosis is the movement of water molecules through a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration.
Question 9
Potato Osmosis Experiment
(i) Explain why water gathers in the hollowed portion of B and C.
Answer:
Sugar (B) and salt (C) create a hypertonic solution inside the potato cup.
Water moves from the surrounding dilute solution into the cup by osmosis, so water gathers inside.
(ii) Why is potato A necessary for this experiment?
Answer:
Potato A acts as a control to show that osmosis does not occur without a solute inside the potato cup.
(iii) Explain why water does not gather in the hollowed portions of A and D.
Answer:
-
A: No solute is present, so no concentration difference exists.
-
D: Boiling destroys the living cells and the selectively permeable membrane, so osmosis does not occur.
Question 10
Which type of cell division is required for growth and repair of body and which type is involved in formation of gametes?
Answer:
-
Mitosis is required for growth and repair of the body
-
Meiosis is involved in the formation of gametes