Cell — The Building Block of Life — Practice

Question 1

Who first observed and named 'cells', and in what material?

Accepted Answer

Robert Hooke, in 1665, observed boxes in a thin slice of cork and named them cells.

✦ Answer: Robert Hooke, in cork.

Question 2

Convert 50 µm into millimetres.

Accepted Answer

Step 1 — 1 mm = 1000 µm.

Step 2 — 50 µm = 50/1000 mm = 0.05 mm.

✦ Answer: 0.05 mm.

Question 3

Which organelle is called the powerhouse of the cell and why?

Accepted Answer

Mitochondria — they release energy as ATP during cellular respiration.

✦ Answer: Mitochondria (release ATP).

Question 4

A raisin is soaked in plain water and swells up. Explain why, using the term osmosis.

Accepted Answer

Step 1 — The raisin's cell sap is more concentrated than the surrounding plain water (hypotonic outside).

Step 2 — Water moves by osmosis from the dilute outside into the concentrated cell sap across the selectively permeable membrane.

Step 3 — The cells take in water and the raisin swells.

✦ Answer: water enters the raisin by osmosis (dilute → concentrated).

Question 5

Give two differences between a prokaryotic and a eukaryotic cell.

Accepted Answer

1) Prokaryotic cells have no true (membrane-bound) nucleus — only a nucleoid; eukaryotic cells have a true nucleus.

2) Prokaryotic cells lack membrane-bound organelles (mitochondria, ER); eukaryotic cells have them.

✦ Answer: nucleus and membrane-bound organelles.

Question 6

List three structures present in a plant cell but absent in an animal cell.

Accepted Answer

Cell wall (cellulose), plastids (e.g. chloroplasts), and a large central vacuole.

✦ Answer: cell wall, plastids, large central vacuole.

Question 7

A plant cell is placed in a strong salt solution. State what happens and what it proves.

Accepted Answer

Step 1 — The outside is hypertonic (more concentrated) than the cell sap.

Step 2 — Water leaves the cell by osmosis; the cytoplasm and membrane shrink and pull away from the cell wall — this is plasmolysis.

Step 3 — Only a living cell can plasmolyse, so the experiment proves the cell was alive.

✦ Answer: it plasmolyses; this proves the cell was living.

Question 8

Match the job to the organelle: (i) packaging and dispatch, (ii) protein synthesis, (iii) intracellular digestion.

Accepted Answer

(i) Golgi apparatus — modifies, packages and dispatches materials.

(ii) Ribosomes — synthesise proteins.

(iii) Lysosomes — contain digestive enzymes; the 'suicide bags'.

✦ Answer: Golgi, ribosomes, lysosomes.

Practice — Cell — The Building Block of Life