Biology Test Biology Cell Structure & Function 3 — Questions and Answers
Question 1: A cell placed in a hypertonic solution will most likely:
- Swell and potentially burst
- Shrink due to water loss by osmosis (Correct answer)
- Remain unchanged because concentration is equal
- Actively pump solutes outward
Correct answer: Shrink due to water loss by osmosis
In a hypertonic solution, the solute concentration outside is higher than inside the cell, so water moves out by osmosis, causing the cell to shrink (crenation in animal cells).
Question 2: Which of the following best describes the fluid mosaic model of the plasma membrane?
- A rigid lattice of proteins embedded in a solid lipid layer
- A dynamic phospholipid bilayer with mobile embedded proteins and cholesterol (Correct answer)
- A single layer of phospholipids with proteins only on the outer surface
- A carbohydrate matrix supported by a protein scaffold
Correct answer: A dynamic phospholipid bilayer with mobile embedded proteins and cholesterol
The fluid mosaic model describes the membrane as a flexible phospholipid bilayer in which proteins, cholesterol, and glycolipids can move laterally.
Question 3: What happens to a plant cell in a hypotonic solution?
- It lyses because it lacks a cell wall
- It becomes turgid as water enters but is restrained by the cell wall (Correct answer)
- It undergoes plasmolysis
- It loses chlorophyll
Correct answer: It becomes turgid as water enters but is restrained by the cell wall
Water enters the plant cell by osmosis, increasing internal pressure (turgor pressure), but the rigid cell wall prevents lysis, making the cell turgid.
Question 4: Which protein channel facilitates the passive transport of water across the cell membrane?
- Ion channels
- Aquaporins (Correct answer)
- ATP-binding cassette transporters
- Carrier proteins
Correct answer: Aquaporins
Aquaporins are specialized channel proteins that allow rapid, selective transport of water molecules across the plasma membrane without energy expenditure.
Question 5: During endocytosis, a cell engulfs a large solid particle by extending pseudopods around it. This specific process is called:
- Pinocytosis
- Exocytosis
- Phagocytosis (Correct answer)
- Receptor-mediated endocytosis
Correct answer: Phagocytosis
Phagocytosis ('cell eating') involves the engulfment of large particles or microorganisms by extending pseudopods that fuse to form a phagosome.
Question 6: The sodium-potassium pump maintains the resting membrane potential by:
- Moving 2 Na⁺ out and 3 K⁺ in per cycle
- Moving 3 Na⁺ out and 2 K⁺ in per cycle using ATP (Correct answer)
- Allowing Na⁺ and K⁺ to diffuse freely down concentration gradients
- Pumping Na⁺ and K⁺ in equal amounts in the same direction
Correct answer: Moving 3 Na⁺ out and 2 K⁺ in per cycle using ATP
The Na⁺/K⁺-ATPase uses one ATP to pump 3 sodium ions out of the cell and 2 potassium ions in, generating an electrochemical gradient.
Question 7: Gap junctions in animal cells primarily allow:
- Structural support between adjacent cells
- Direct cytoplasmic communication between neighboring cells (Correct answer)
- Passage of large proteins between cells
- Immune recognition of self vs. non-self
Correct answer: Direct cytoplasmic communication between neighboring cells
Gap junctions are channels formed by connexin proteins that connect the cytoplasm of adjacent cells, allowing ions and small molecules to pass directly between them.
Biology Test Biology Cell Structure & Function 3
A cell placed in a hypertonic solution will most likely: