Free Animal and Plant Cell MCQs with Answers

11. Plasmolysis is said to occur when

• A. a plant cell takes in water and becomes turgid
• B. the protoplast of a plant cell shrinks away from the cell wall in a concentrated solution
• C. the cell wall dissolves completely
• D. the nucleus divides into two

Explanation: In a solution of lower water potential than the cell sap, water leaves the vacuole, the protoplast contracts and pulls away from the wall, and the cell becomes flaccid and then plasmolysed. Because the wall is fully permeable, the external solution simply fills the space between it and the shrunken protoplast. The process can be reversed if the cell is returned to water soon enough.

12. The primary cell wall of a plant cell is composed mainly of

• A. cellulose
• B. chitin
• C. peptidoglycan
• D. lignin

Explanation: Cellulose microfibrils, polymers of beta glucose, give the plant wall its strength, while chitin builds fungal walls and peptidoglycan bacterial ones. Lignin is a secondary strengthening chemical laid down later in woody tissue, not the primary wall material.

13. The middle lamella, which cements neighbouring plant cells together, is composed mainly of

• A. cellulose
• B. pectin
• C. lignin
• D. suberin

Explanation: The middle lamella is a shared pectin-rich layer formed first during cell division, gluing adjacent walls together. Cellulose makes up the wall itself on each side of it, and suberin is the waterproofing of cork, not the cementing layer.

14. As a cell grows larger, its surface area to volume ratio

• A. increases steadily
• B. remains constant
• C. decreases
• D. first falls and then rises again

Explanation: Volume grows with the cube of the radius while surface area grows only with the square, so a larger cell has proportionally less membrane through which to feed its cytoplasm. This falling ratio is one of the main reasons cells divide instead of growing indefinitely.

15. The engulfing of solid food particles by a cell through infolding of its membrane is called

• A. pinocytosis
• B. osmosis
• C. facilitated diffusion
• D. phagocytosis

Explanation: Phagocytosis, literally cell eating, wraps the membrane around a particle to form a vacuole, as white blood cells do to bacteria. Pinocytosis is the drinking of fluid droplets, and both are forms of endocytosis that need membrane, unlike diffusion.

16. Pinocytosis differs from phagocytosis in that pinocytosis

• A. engulfs large solid particles
• B. occurs without any membrane
• C. takes in dissolved substances in tiny droplets of fluid
• D. occurs only in plant cells

Explanation: Pinocytosis brings in small vesicles of extracellular fluid with dissolved solutes, while phagocytosis handles solid particles. Both require the plasma membrane to fold inward, and both occur in animal cells, so neither of those features separates them.

17. Exocytosis is the process by which a cell

• A. releases materials in vesicles that fuse with the plasma membrane
• B. takes in fluid droplets from its surroundings
• C. pumps ions against their concentration gradient
• D. divides its cytoplasm during cell division

Explanation: Secretory vesicles from the Golgi move to the surface and merge with the membrane, discharging their contents outside, which is how enzymes, hormones and neurotransmitters leave the cell. The reverse process is endocytosis, and ion pumping is active transport.

18. A solution in which a red blood cell shrinks and becomes wrinkled is described as

• A. isotonic
• B. hypotonic
• C. pure water
• D. hypertonic

Explanation: In a hypertonic solution the external solute concentration is higher, so water leaves the cell by osmosis and it crenates. In a hypotonic solution the same cell would swell and burst, while isotonic saline keeps it unchanged.

19. Facilitated diffusion differs from simple diffusion in that it

• A. requires energy from ATP
• B. uses specific carrier or channel proteins in the membrane
• C. moves substances against their concentration gradient
• D. occurs only through the lipid portion of the membrane

Explanation: Facilitated diffusion still follows the concentration gradient and costs no energy, but polar molecules and ions pass through specific protein channels or carriers. Needing ATP or moving against the gradient would make it active transport, a common trap in the comparison.

20. A prokaryotic cell contains all of the following EXCEPT

• A. cytoplasm
• B. a nuclear envelope
• C. ribosomes
• D. a plasma membrane

Explanation: The defining absence in a prokaryote is a membrane-bound nucleus; its DNA lies free in the nucleoid. It still has cytoplasm, 70S ribosomes and a plasma membrane, since those are requirements of every living cell.