Question 1

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

Accepted Answer

A flexible structure with proteins, lipids, and carbohydrates embedded in a phospholipid bilayer.

Question 2

Phospholipids in the plasma membrane are described as amphipathic. What does this mean?

Accepted Answer

They have both hydrophilic and hydrophobic regions.

Question 3

Which of the following molecules can most easily cross the lipid bilayer without the help of membrane proteins?

Accepted Answer

Small nonpolar molecules such as $O_2$.

Question 4

A red blood cell is placed in a hypertonic solution. What will happen to the cell?

Accepted Answer

It will shrink as water leaves the cell.

Question 5

Which of the following is a function of membrane proteins?

Accepted Answer

Facilitating communication and transport across the membrane.

Question 6

What is the main difference between passive transport and active transport across cell membranes?

Accepted Answer

Passive transport moves molecules down their concentration gradient, while active transport moves molecules against their concentration gradient using energy.

Question 7

Which equation best represents the movement of water during osmosis?

Accepted Answer

$\Delta \Psi = \Psi_s + \Psi_p$

Question 8

Facilitated diffusion differs from simple diffusion in that:

Accepted Answer

Facilitated diffusion uses membrane proteins to transport molecules down their concentration gradient.

Question 9

The sodium-potassium pump is an example of:

Accepted Answer

Active transport that moves $3 \ Na^+$ out and $2 \ K^+$ in per ATP hydrolyzed.

Question 10

Which factor increases membrane fluidity?

Accepted Answer

Increasing the proportion of unsaturated fatty acids.

Question 11

A plant cell placed in a hypotonic solution will:

Accepted Answer

Become turgid as water enters the cell.

Question 12

Which of the following best explains why ions cannot easily cross the lipid bilayer?

Accepted Answer

Ions are repelled by the hydrophobic core of the bilayer.

Question 13

Which type of membrane protein is most likely to function as a channel for ions?

Accepted Answer

Integral transmembrane protein.

Question 14

What is the role of glycoproteins in the plasma membrane?

Accepted Answer

They are involved in cell recognition and signaling.

Question 15

Which of the following best describes cotransport?

Accepted Answer

Movement of one molecule down its gradient coupled to the movement of another molecule against its gradient.

Question 16

A cell uses a proton pump to create a gradient. What is the main purpose of this gradient?

Accepted Answer

To drive the cotransport of other molecules such as sucrose.

Question 17

Which of the following is true about facilitated diffusion and active transport?

Accepted Answer

Facilitated diffusion moves molecules down their concentration gradient, while active transport moves molecules against their gradient.

Question 18

Which equation describes the electrochemical gradient for an ion across a membrane?

Accepted Answer

$\Delta \mu = RT \ln \left( \frac{[C]_	ext{in}}{[C]_	ext{out}} ight) + zF\Delta \Psi$

Question 19

Large molecules such as proteins and polysaccharides are transported across membranes by:

Accepted Answer

Endocytosis and exocytosis.

Question 20

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

Accepted Answer

Cholesterol helps maintain membrane fluidity at both high and low temperatures.

M6-Structure and Function of Cell Membranes: Study Guide

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