Question 1

Which statement best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

The membrane is a dynamic structure with proteins and lipids able to move laterally within the bilayer.

Question 2

A red blood cell placed in a hypertonic solution will:

Accepted Answer

Shrink as water leaves the cell by osmosis.

Question 3

Which of the following best explains why plant cells do not burst when placed in a hypotonic solution?

Accepted Answer

Plant cells have a rigid cell wall that resists osmotic pressure.

Question 4

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Energy production via photosynthesis.

Question 5

What is the main difference between passive and active transport across the plasma membrane?

Accepted Answer

Passive transport moves substances down their concentration gradient without energy input, while active transport moves substances against the gradient using energy.

Question 6

Which equation correctly represents the movement of water during osmosis?

Accepted Answer

$\Delta \Psi = \Psi_{s} + \Psi_{p}$

Question 7

A cell is placed in a solution with a lower solute concentration than its cytoplasm. What type of solution is this, and what will happen to the cell?

Accepted Answer

Hypotonic; the cell will gain water and may burst.

Question 8

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules through the membrane via carrier or channel proteins, down their concentration gradient, without energy input.

Question 9

The sodium-potassium pump moves ions across the plasma membrane. For each cycle, how many $\mathrm{Na^+}$ ions are moved out and how many $\mathrm{K^+}$ ions are moved in?

Accepted Answer

3 $\mathrm{Na^+}$ out, 2 $\mathrm{K^+}$ in

Question 10

Which of the following is a real-life example of receptor-mediated endocytosis?

Accepted Answer

Uptake of cholesterol via LDL receptors in human cells.

Question 11

Which of the following statements about cholesterol in the plasma membrane is correct?

Accepted Answer

Cholesterol increases membrane fluidity at high temperatures and decreases it at low temperatures.

Question 12

Which process is responsible for the secretion of neurotransmitters from nerve cells?

Accepted Answer

Exocytosis

Question 13

Which of the following best describes the role of aquaporins in the plasma membrane?

Accepted Answer

They facilitate the rapid passive movement of water across the membrane.

Question 14

Which of the following is true about integral membrane proteins?

Accepted Answer

They span the entire membrane and are involved in transport and signaling.

Question 15

A cell uses ATP to move $\mathrm{Na^+}$ ions out of the cell against their concentration gradient. This is an example of:

Accepted Answer

Active transport

Question 16

Which of the following best describes phagocytosis?

Accepted Answer

A cell engulfs large particles or microorganisms by forming a vesicle.

Question 17

Which term describes the ability of a biological membrane to allow some substances to pass while blocking others?

Accepted Answer

Selective permeability

Question 18

Which of the following is a consequence of placing a plant cell in a solution with a lower water potential than the cell's cytoplasm?

Accepted Answer

The cell undergoes plasmolysis.

Question 19

Which of the following best explains cotransport in biological membranes?

Accepted Answer

The movement of one substance down its gradient drives the active transport of another substance against its gradient.

Question 20

Which of the following is a correct description of exocytosis?

Accepted Answer

The process by which cells release large molecules by fusion of vesicles with the plasma membrane.

Cell Membrane Structure and Transport Mechanisms: Study Guide

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