Question 1

Which of the following best explains why lipids are not considered polymers?

Accepted Answer

Lipids are made of long chains of hydrocarbons but lack a repeating subunit structure.

Question 2

A cell membrane is described as a 'fluid mosaic.' What does this mean?

Accepted Answer

The membrane is flexible, with components that move laterally and is made of multiple types of biomolecules.

Question 3

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

Accepted Answer

Small non-polar molecules such as $$O_2$$

Question 4

How does the degree of saturation in fatty acid tails affect membrane fluidity?

Accepted Answer

Unsaturated fatty acid tails with kinks increase membrane fluidity.

Question 5

What is the primary function of cholesterol in the plasma membrane?

Accepted Answer

Cholesterol stabilizes the membrane, making it less fluid at high temperatures and more fluid at low temperatures.

Question 6

Which equation best describes the movement of molecules during simple diffusion across a membrane?

Accepted Answer

$$J = -D \frac{dC}{dx}$$

Question 7

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

Accepted Answer

Water will enter the cell, causing it to swell and possibly burst.

Question 8

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules down their concentration gradient through a protein channel, without energy input.

Question 9

Which property of phospholipids is most responsible for the formation of bilayers in water?

Accepted Answer

Phospholipids are amphipathic, with hydrophilic heads and hydrophobic tails.

Question 10

Which of the following statements about membrane proteins is correct?

Accepted Answer

Integral membrane proteins can span the bilayer and change membrane permeability.

Question 11

A cell is placed in a solution where the solute concentration is higher outside than inside. What type of solution is this, and what will happen to the cell?

Accepted Answer

Hypertonic; the cell will shrink as water leaves.

Question 12

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

Accepted Answer

Allowing all substances to freely enter and leave the cell

Question 13

Which type of transport requires energy to move molecules against their concentration gradient?

Accepted Answer

Active transport

Question 14

What is the effect of increasing the length and saturation of fatty acid tails in a phospholipid bilayer?

Accepted Answer

It decreases membrane permeability.

Question 15

Which of the following best describes osmosis?

Accepted Answer

Movement of water molecules from low solute concentration to high solute concentration.

Question 16

Which of the following molecules would require a protein channel to cross the plasma membrane?

Accepted Answer

Sodium ion ($$Na^+)$$

Question 17

Which of the following is a correct statement about the permeability of the phospholipid bilayer?

Accepted Answer

Small non-polar molecules can diffuse freely through the bilayer.

Question 18

Which of the following best explains why butter is solid at room temperature while olive oil is liquid?

Accepted Answer

Butter contains short, saturated fatty acid chains, while olive oil contains short, unsaturated chains.

Question 19

Which of the following is true about aquaporins?

Accepted Answer

Aquaporins increase the rate of osmosis by allowing water to move rapidly across the membrane.

Biomolecules II: Lipids and Membranes – Structure, Properties, and Transport

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