Question 1

Which of the following best explains why phospholipids spontaneously form bilayers in water?

Accepted Answer

Phospholipids have both hydrophilic heads and hydrophobic tails, causing them to arrange with heads facing water and tails facing inward.

Question 2

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

Accepted Answer

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

Question 3

Which of the following molecules would most rapidly cross a pure phospholipid bilayer without the help of a transport protein?

Accepted Answer

O$_2$

Question 4

Which statement best describes the effect of cholesterol on membrane fluidity at moderate temperatures?

Accepted Answer

Cholesterol decreases membrane fluidity by packing phospholipids closer together.

Question 5

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

Accepted Answer

Unsaturated fatty acids have bent chains due to double bonds, preventing tight packing and increasing permeability.

Question 6

A researcher creates artificial membrane-bound vesicles (liposomes) and adds a small, nonpolar molecule to the solution. What is the most likely outcome?

Accepted Answer

The molecule will rapidly diffuse across the membrane into the vesicle.

Question 7

Which equation correctly represents the movement of water during osmosis across a semipermeable membrane?

Accepted Answer

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

Question 8

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

Accepted Answer

Synthesizing proteins for the cell

Question 9

A mutation causes a defect in a transmembrane carrier protein. Which process would be most directly affected?

Accepted Answer

Facilitated diffusion of specific molecules

Question 10

Which of the following best describes the sodium-potassium pump's role in cells?

Accepted Answer

It uses ATP to move sodium out and potassium into the cell against their concentration gradients.

Question 11

If a cell membrane is composed primarily of saturated fatty acids, what effect would this have on membrane permeability?

Accepted Answer

Membrane permeability would decrease due to tight packing.

Question 12

Which of the following statements about passive transport is correct?

Accepted Answer

Passive transport moves substances down their concentration gradient.

Question 13

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

Accepted Answer

There will be no net movement of water, and the cell will maintain its shape.

Question 14

Which of the following best describes the role of detergents in studying membrane proteins?

Accepted Answer

Detergents are amphipathic molecules that can isolate proteins from membranes by disrupting lipid bilayers.

Question 15

Which of the following would most likely increase the rate of facilitated diffusion across a membrane?

Accepted Answer

Increasing the number of carrier proteins in the membrane

Question 16

Which of the following is a correct statement about the movement of ions through ion channels?

Accepted Answer

Ion channels allow ions to move passively down their electrochemical gradient.

Question 17

Which of the following would decrease the permeability of a cell membrane to water?

Accepted Answer

Replacing unsaturated fatty acids with saturated fatty acids in the membrane

Question 18

A scientist observes that as temperature increases, the permeability of a cell membrane also increases. Which of the following best explains this observation?

Accepted Answer

Higher temperatures increase the kinetic energy of molecules, making it easier for them to cross the membrane.

Question 19

Which of the following is true about the selective permeability of cell membranes?

Accepted Answer

Small nonpolar molecules cross the membrane more easily than large or charged molecules.

Membrane Structure and Function: Lipids, Proteins, and Transport in Cells

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