Question 1

Which of the following best explains why cells are generally small in size?

Accepted Answer

Smaller cells have a higher surface area-to-volume ratio, allowing efficient exchange of materials with their environment.

Question 2

A spherical cell increases its diameter from 10 μm to 20 μm. By what factor does its surface area-to-volume ratio change?

Accepted Answer

It decreases by a factor of 2.

Question 3

Which of the following statements about the fluid mosaic model of the plasma membrane is correct?

Accepted Answer

Phospholipids and proteins can move laterally within the layer, contributing to membrane fluidity.

Question 4

Which of the following would most likely increase the fluidity of a cell membrane at low temperatures?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in phospholipids.

Question 5

A cell is placed in a hypertonic solution. What will most likely happen to the cell?

Accepted Answer

It will lose water and shrink.

Question 6

Which of the following molecules can most easily cross a pure phospholipid bilayer by simple diffusion?

Accepted Answer

Oxygen (O$_2$)

Question 7

Which type of membrane protein is primarily responsible for facilitated diffusion of ions across the plasma membrane?

Accepted Answer

Channel proteins

Question 8

A red blood cell is placed in pure water. Which of the following best describes what happens and why?

Accepted Answer

Water enters the cell by osmosis, causing it to swell and potentially lyse.

Question 9

Which of the following best describes active transport across a cell membrane?

Accepted Answer

Movement of substances against their concentration gradient using energy, often from ATP.

Question 10

The sodium-potassium pump (Na$^+$/K$^+$-ATPase) is an example of which type of membrane transport?

Accepted Answer

Primary active transport

Question 11

Which of the following best explains why polar molecules such as glucose require transport proteins to cross the plasma membrane?

Accepted Answer

The hydrophobic core of the lipid bilayer prevents polar molecules from diffusing through.

Question 12

Which of the following scenarios best illustrates the concept of cotransport (secondary active transport)?

Accepted Answer

The movement of glucose into a cell is coupled to the movement of sodium ions down their concentration gradient.

Question 13

Which of the following is a function of membrane carbohydrates?

Accepted Answer

Cell-cell recognition

Question 14

A plant cell is placed in a hypotonic solution. What is the most likely outcome?

Accepted Answer

The cell becomes turgid as water enters, but does not burst due to the cell wall.

Question 15

Which process involves the engulfment of large particles by the cell membrane to form an internal vesicle?

Accepted Answer

Phagocytosis

Question 16

Which of the following best describes the role of cholesterol in animal cell membranes?

Accepted Answer

It helps maintain membrane fluidity at different temperatures.

Question 17

A solution contains a higher concentration of solute than the cytoplasm of a cell. What term describes this solution relative to the cell?

Accepted Answer

Hypertonic

Question 18

Which of the following equations correctly represents the surface area-to-volume ratio for a cube-shaped cell with side length $l$?

Accepted Answer

$\frac{6l^2}{l^3}$

Question 19

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

Accepted Answer

Synthesis of DNA

Question 20

A cell is placed in a solution where the solute concentration is equal inside and outside the cell. What will happen to the movement of water?

Accepted Answer

Water will move in and out at equal rates, resulting in no net change in cell volume.

Cell Membranes: Structure, Function, and Transport Mechanisms

Study Guide - Practice Questions