Question 1

Which of the following best describes selective permeability in biological membranes?

Accepted Answer

The property of a membrane that allows certain molecules to cross more easily than others.

Question 2

In an artificial membrane experiment, which variable would most directly test the effect of phospholipid composition on membrane permeability?

Accepted Answer

Using different types of phospholipids to construct the membrane.

Question 3

A lipid bilayer with many unsaturated fatty acids will have ______ permeability compared to a bilayer with no unsaturated fatty acids.

Accepted Answer

Higher

Question 4

Which of the following factors would decrease the permeability of a lipid bilayer to small molecules?

Accepted Answer

Increasing the cholesterol content.

Question 5

Based on the experimental data shown, what is the relationship between temperature and membrane permeability to glycerol?

Accepted Answer

Membrane permeability to glycerol increases as temperature increases.

Question 6

If a cell is placed in a hypertonic solution, what will happen to the cell?

Accepted Answer

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

Question 7

Which of the following is a real-world example of a cell maintaining homeostasis in a hypotonic environment?

Accepted Answer

A Paramecium using contractile vacuoles to expel excess water.

Question 8

Which type of membrane transport requires energy input from the cell?

Accepted Answer

Active transport

Question 9

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

Accepted Answer

Passive transport moves molecules with their concentration gradient, while active transport moves them against the gradient using energy.

Question 10

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

Accepted Answer

$$\Delta \Psi = \Psi_{inside} - \Psi_{outside}$$

Question 11

A potassium channel in a cell membrane is highly selective. What property allows it to only permit potassium ions to pass?

Accepted Answer

The channel's size and charge distribution match those of potassium ions.

Question 12

Which of the following is true about facilitated diffusion?

Accepted Answer

It uses membrane proteins to move molecules down their concentration gradient.

Question 13

The sodium-potassium pump (Na+/K+-ATPase) moves sodium and potassium ions across the membrane. Which equation best describes the stoichiometry of this pump?

Accepted Answer

$$3 	ext{Na}^+_{out} : 2 	ext{K}^+_{in}$$ per ATP hydrolyzed

Question 14

Which of the following would most likely increase the rate of glucose transport into a cell via facilitated diffusion?

Accepted Answer

Increasing the number of GLUT transporters in the membrane.

Question 15

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

There will be no net change in cell volume.

Question 16

Tetrodotoxin, found in puffer fish, blocks sodium channels. What effect would this have on nerve cells?

Accepted Answer

It would prevent sodium ions from entering the cell, inhibiting action potentials.

Question 17

Which of the following best explains why cholesterol decreases membrane permeability?

Accepted Answer

Cholesterol fills spaces between phospholipids, making the membrane less flexible and less permeable.

Question 18

Which of the following is NOT a factor that affects membrane permeability?

Accepted Answer

Presence of ribosomes

Question 19

A cell uses the sodium-potassium pump to maintain a gradient. What is the energy source for this process?

Accepted Answer

ATP hydrolysis

Question 20

Which of the following statements about membrane channels and carrier proteins is correct?

Accepted Answer

Channels allow passive movement of molecules, while carriers can be involved in both passive and active transport.

Selective Permeability of Lipid Bilayers and Factors Affecting Membrane Transport

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