Cell structure, organelles, membrane transport, prokaryote vs eukaryote MCQs

Q1. Consider the chronology: I. Robert Hooke observed dead cork cells. II. Leeuwenhoek observed free living cells. III. Robert Brown discovered the nucleus. IV. Schleiden and Schwann proposed cell theory. V. Virchow stated Omnis cellula e cellula. Which option gives the correct chronological order?

• A.I → II → III → IV → V
• B.I → III → II → IV → V
• C.II → I → III → V → IV
• D.I → II → IV → III → V

Answer: A. I → II → III → IV → V

What this question tests: Hooke's observation of cork dates to 1665, Leeuwenhoek's living unicellular observations followed in the 1670s, Brown identified the nucleus in 1831, Schleiden and Schwann formulated the original cell theory in 1838-39, and Virchow's omnis-cellula extension came in 1855. Thus the historically correct sequence is I → II → III → IV → V. Thus the correct option is A) I → II → III → IV → V.

Q2. Which experiment best demonstrates osmosis using a simple kitchen setup?

• A.Filling a peeled hollow potato with sugar solution and placing it in water
• B.Heating sugar in a frying pan until it melts
• C.Dissolving common salt in water and tasting it
• D.Mixing two coloured liquids in a glass jar

Answer: A. Filling a peeled hollow potato with sugar solution and placing it in water

The idea this question leans on: The classical potato osmoscope uses a hollowed peeled potato filled with sugar solution dipped in water; water enters the potato through its semi-permeable cells into the sugar cavity, raising the level - a clear demonstration of osmosis. Melting sugar, tasting salt water and mixing coloured liquids do not illustrate osmosis through a semi-permeable membrane. Hence the answer is A) Filling a peeled hollow potato with sugar solution and placing it in water.

Q3. Which statement is INCORRECT regarding plasmolysis?

• A.Plasmolysis is irreversible regardless of the duration of exposure
• B.Plasmolysis occurs when a plant cell is placed in a hypertonic solution
• C.During plasmolysis, the protoplast shrinks from the cell wall
• D.Plasmolysis can be reversed by placing the cell in a hypotonic solution if it has not been irreversibly damaged

Answer: A. Plasmolysis is irreversible regardless of the duration of exposure

The principle at play: Plasmolysis is reversible by deplasmolysis if the cell is transferred to a hypotonic solution before damage occurs. It happens in hypertonic media, with the protoplast shrinking from the wall as water exits. Hence the false statement is that plasmolysis is always irreversible. Therefore the correct option is A) Plasmolysis is irreversible regardless of the duration of exposure.