$$\text{Water moves from regions of low solute concentration to regions of high solute concentration}$$

$$3\ \text{Na}^{+}\ \text{out},\ 2\ \text{K}^{+}\ \text{in},\ \text{using}\ \text{ATP}$$

Question 1

Which of the following best describes the amphipathic nature of phospholipids in biological membranes?

Accepted Answer

Phospholipids have both a hydrophilic head and hydrophobic tails, allowing them to form bilayers in water.

Question 2

A cell is placed in a solution and begins to swell until it bursts. Which term best describes the solution relative to the cell’s interior?

Accepted Answer

Hypotonic

Question 3

Which of the following molecules would most rapidly cross a pure phospholipid bilayer without the aid of membrane proteins?

Accepted Answer

O$$_2$$

Question 4

What effect does increasing the number of double bonds in the fatty acid tails of phospholipids have on membrane permeability?

Accepted Answer

It increases membrane permeability by preventing close packing of tails.

Question 5

Which equation best represents the movement of water during osmosis across a selectively permeable membrane?

Accepted Answer

$$	ext{Water moves from regions of low solute concentration to regions of high solute concentration}$$

Question 6

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

Accepted Answer

Proteins are embedded within the lipid bilayer, creating a dynamic mosaic.

Question 7

A researcher adds cholesterol to a sample of artificial membranes. What is the most likely effect on membrane permeability?

Accepted Answer

Membrane permeability will decrease because cholesterol increases membrane density.

Question 8

Which of the following is a correct description of active transport across a membrane?

Accepted Answer

Active transport moves substances against their concentration gradient using ATP.

Question 9

The sodium-potassium pump (Na$$^{+}/K$^{+}-$$ATPase) uses ATP to move ions across the plasma membrane. Which equation best describes its action?

Accepted Answer

$$3\ 	ext{Na}^{+}\ 	ext{out},\ 2\ 	ext{K}^{+}\ 	ext{in},\ 	ext{using}\ 	ext{ATP}$$

Question 10

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Double bonds create kinks, preventing tight packing of tails.

Question 11

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

Accepted Answer

Water will move out of the cell, causing it to shrink.

Question 12

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

Accepted Answer

Forming the basic structure of the lipid bilayer

Question 13

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

Facilitated diffusion moves substances down their concentration gradient via transport proteins.

Question 14

Which of the following factors would decrease the permeability of a phospholipid bilayer?

Accepted Answer

Adding more cholesterol molecules to the membrane

Question 15

Which class of membrane proteins is primarily responsible for moving ions down their electrochemical gradient?

Accepted Answer

Channel proteins

Question 16

Which of the following best describes the process of diffusion?

Accepted Answer

Random movement of molecules resulting in net movement from high to low concentration

Question 17

Which of the following is a correct statement about the selective permeability of the plasma membrane?

Accepted Answer

Small nonpolar molecules cross the membrane rapidly.

Question 18

Which of the following is a correct description of the role of the GLUT-1 transporter?

Accepted Answer

GLUT-1 facilitates the passive diffusion of glucose down its concentration gradient.

Question 19

Which of the following statements about the movement of phospholipids within the bilayer is correct?

Accepted Answer

Phospholipids move laterally within the same layer of the bilayer.

The Structure and Function of Biological Membranes

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