1. Can you name the two organelles we have studied that contain their own genetic material?
- Mitochondria and chloroplasts contain their own genetic material (DNA). This allows them to synthesize some of their proteins independently.
2. If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen?
- If the cell’s organization is disrupted, it will lose its ability to perform essential functions like respiration, growth, and reproduction. Ultimately, the cell will die.
3. Why are lysosomes known as suicide bags?
- Lysosomes are called suicide bags because they contain digestive enzymes that can break down all types of biomolecules. If the lysosome bursts, these enzymes can digest the cell itself, leading to cell death.
4. Where are proteins synthesized inside the cell?
- Proteins are synthesized in the ribosomes, which can either be free-floating in the cytoplasm or attached to the rough endoplasmic reticulum (RER).
Exercises
1. Compare plant cells and animal cells.
| Feature | Plant Cell | Animal Cell |
| Cell wall | Present (made of cellulose) | Absent |
| Chloroplasts | Present (for photosynthesis) | Absent |
| Vacuole | Large central vacuole | Small or absent |
| Shape | Rectangular or box-like shape | Round or irregular shape |
| Centrioles | Absent | Present (involved in cell division) |
2. How is a prokaryotic cell different from a eukaryotic cell?
| Feature | Prokaryotic Cell | Eukaryotic Cell |
| Nucleus | No nucleus (nucleoid region present) | True nucleus with nuclear membrane |
| Organelles | No membrane-bound organelles | Membrane-bound organelles present |
| Size | Smaller (1-10 µm) | Larger (10-100 µm) |
| DNA | Circular DNA without histones | Linear DNA with histones |
| Examples | Bacteria, Archaea | Plants, Animals, Fungi, Protists |
3. What would happen if the plasma membrane ruptures or breaks down?
- If the plasma membrane breaks down, the contents of the cell would leak out, and the cell would lose its integrity, leading to cell death.
4. What would happen to the life of a cell if there was no Golgi apparatus?
- Without the Golgi apparatus, the cell would not be able to modify, package, and transport proteins and lipids. This would disrupt essential cellular processes, including secretion and lysosome formation.
5. Which organelle is known as the powerhouse of the cell? Why?
- The mitochondria is known as the powerhouse of the cell because it produces energy in the form of ATP (adenosine triphosphate) during cellular respiration.
6. Where do the lipids and proteins constituting the cell membrane get synthesized?
- Lipids are synthesized in the smooth endoplasmic reticulum (SER).
- Proteins are synthesized in the ribosomes, often attached to the rough endoplasmic reticulum (RER).
7. How does an Amoeba obtain its food?
- An Amoeba engulfs food particles through a process called phagocytosis, where it forms temporary projections called pseudopodia to surround and take in food into a food vacuole for digestion.
8. What is osmosis?
- Osmosis is the movement of water molecules through a semipermeable membrane from an area of higher water concentration to an area of lower water concentration.
9. Osmosis Experiment:
(i) Explain why water gathers in the hollowed portions of B and C.
- Water moves into cups B and C because the sugar and salt create a region of low water concentration (higher solute concentration), causing water to enter by osmosis.
(ii) Why is potato A necessary for this experiment?
- Potato A acts as a control to show that water does not move into a hollowed potato cup without solute.
(iii) Explain why water does not gather in the hollowed-out portions of A and D.
- In cup A, there is no solute, so no osmotic gradient exists to draw water in.
- In cup D, the potato is boiled, so its cell membranes are damaged, preventing osmosis.
10. Which type of cell division is required for the growth and repair of the body and which type is involved in the formation of gametes?
- Mitosis: Required for growth and repair as it produces identical cells.
- Meiosis: Involved in the formation of gametes, producing cells with half the chromosome number.