9 Class – The Fundamental Unit of Life
Exercises at the end of the lesson (Page 22)
1. Make a comparison: Plant cells vs Animal cells
Plant Cell
Animal Cell
i. Cell wall present
i. Cell wall absent
ii. Plastids present
ii. Plastids absent
iii. Large vacuole
iii. Small or no vacuole
iv. Fixed shape
iv. Irregular shape
2. How is a prokaryotic cell different from a eukaryotic cell?
Prokaryotic Cell
Eukaryotic Cell
i. Small size
i. Large size
ii. No true nucleus
ii. True nucleus present
iii. Single chromosome
iii. Multiple chromosomes
iv. No membrane-bound organelles
iv. Membrane-bound organelles present
3. What would happen if the plasma membrane ruptures or breaks down?
i. Substances move freely in and out.
ii. Controlled exchange stops.
iii. Protoplasm leaks out.
iv. The cell dies.
4. What would happen if there was no Golgi apparatus?
i. Proteins cannot be packed.
ii. Transport of materials stops.
iii. Cell formation is affected.
iv. Cell functions fail.
5. Which organelle is known as the powerhouse of the cell? Why?
i. Mitochondria is the powerhouse.
ii. It produces ATP.
iii. ATP provides energy for life activities.
6. Where are lipids and proteins of the cell membrane synthesised?
i. Lipids are synthesised in smooth ER.
ii. Proteins are synthesised in rough ER.
7. How does an Amoeba obtain its food?
i. By endocytosis.
ii. Food is engulfed using pseudopodia.
iii. A food vacuole is formed.
iv. Digestion occurs inside the vacuole.
8. What is osmosis?
i. Movement of water molecules.
ii. From higher to lower concentration.
iii. Through a semipermeable membrane.
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.
(i) Why does water gather in B and C?
i. Sugar and salt create concentration difference.
ii. Endosmosis occurs.
(ii) Why is potato A necessary?
i. It acts as a control.
ii. Shows no osmosis without solute.
(iii) Why no water in A and D?
i. A has no concentration difference.
ii. D has dead cells (boiled).
iii. No semipermeable membrane.
10. Which cell division is required for growth and for gamete formation?
i. Mitosis – growth and repair.
ii. Meiosis – formation of gametes.
Exercise – 5.1
1. Who discovered cells, and how?
i. Cells were discovered by Robert Hooke.
ii. He observed a thin slice of cork under a microscope in 1665.
iii. He saw small box-like structures like a honeycomb.
iv. These structures were named cells.
2. Why is the cell called the structural and functional unit of life?
i. All living organisms are made of cells.
ii. Cells perform basic life processes like respiration and excretion.
iii. In unicellular organisms, one cell performs all functions.
iv. Hence, cells are the structural and functional units of life.
Exercise – 5.2.1
3. How do substances like CO₂ and water move in and out of the cell? Discuss.
CO₂:
i. CO₂ moves by diffusion.
ii. It moves from higher concentration inside to lower concentration outside.
Water:
i. Water moves by osmosis.
ii. It passes through a selectively permeable membrane.
iii. It moves from higher water concentration to lower concentration.
4. Why is the plasma membrane called a selectively permeable membrane?
i. It allows only certain substances to pass through.
ii. It restricts the movement of some molecules.
iii. Hence, it is called selectively permeable.
Exercise – 5.2.2 to 5.2.4
5. Fill in the gaps illustrating differences between prokaryotic and eukaryotic cells.
Prokaryotic Cell
Eukaryotic Cell
i. Small size (1–10 µm)
i. Large size (5–100 µm)
ii. No nuclear membrane
ii. Nuclear membrane present
iii. Nucleoid region
iii. Well-defined nucleus
iv. Single chromosome
iv. More than one chromosome
v. No membrane-bound organelles
v. Membrane-bound organelles present
Exercise – 5.2.5
6. Can you name the two organelles that contain their own genetic material?
i. Mitochondria
ii. Plastids
7. If the organisation of a cell is destroyed, what will happen?
i. Lysosomes burst.
ii. Enzymes digest the cell.
iii. The cell dies.
8. Why are lysosomes known as suicide bags?
i. Lysosomes contain digestive enzymes.
ii. They digest damaged or dead cells.
iii. Hence, they are called suicide bags.
9. Where are proteins synthesised inside the cell?
i. Proteins are synthesised in ribosomes.
ii. Ribosomes are found on rough endoplasmic reticulum.
iii. Hence, ribosomes are called protein factories.