Question 1

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

Accepted Answer

Unsaturated fatty acids have cis double bonds that introduce kinks, preventing tight packing of lipid tails.

Question 2

A patient is found to have a deficiency in essential fatty acids. Which of the following fatty acids must be obtained from the diet to prevent this deficiency?

Accepted Answer

Arachidonate

Question 3

Which of the following best describes the amphipathic nature of membrane lipids?

Accepted Answer

They contain both hydrophilic and hydrophobic regions.

Question 4

Which of the following is a function of cholesterol in the plasma membrane?

Accepted Answer

It modulates membrane fluidity by disrupting the packing of fatty acid tails.

Question 5

Which of the following best explains why the sodium-potassium pump (Na+/K+ ATPase) is classified as a primary active transporter?

Accepted Answer

It directly uses the energy from ATP hydrolysis to move ions against their concentration gradients.

Question 6

Which of the following membrane structures is best described as having a single polar surface and forming from wedge-shaped amphipathic molecules?

Accepted Answer

Micelle

Question 7

A mutation causes a membrane protein to have several charged amino acids within its transmembrane domain. What is the most likely effect on the protein's function?

Accepted Answer

The protein will be less stable in the membrane due to unfavorable interactions with the hydrophobic core.

Question 8

Which of the following best describes the difference between integral and peripheral membrane proteins?

Accepted Answer

Integral proteins span or are embedded in the membrane, while peripheral proteins associate loosely via electrostatic interactions.

Question 9

Which of the following equations correctly represents the Gibbs free energy change ($$\Delta G) $$for the passive transport of a solute across a membrane?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[C]_2}{[C]_1} \right)$$

Question 10

Which of the following best explains why water can slowly diffuse across the lipid bilayer despite being polar?

Accepted Answer

Water is small and uncharged, allowing limited diffusion through the hydrophobic core.

Question 11

Which of the following is a characteristic of lipid rafts in biological membranes?

Accepted Answer

They are enriched in cholesterol and glycosphingolipids and serve as platforms for cell signaling.

Question 12

A researcher is studying a membrane protein that can be removed from the membrane by high salt concentration without disrupting the bilayer. This protein is most likely:

Accepted Answer

A peripheral membrane protein

Question 13

Which of the following best describes the role of flippases in membrane dynamics?

Accepted Answer

They catalyze the movement of specific phospholipids from one leaflet of the bilayer to the other, often using ATP.

Question 14

Which of the following is true regarding the sodium-glucose linked transporter (SGLT) in intestinal epithelial cells?

Accepted Answer

It uses the sodium gradient established by the Na+/K+ ATPase to drive glucose uptake against its concentration gradient.

Question 15

Which of the following statements about membrane asymmetry is correct?

Accepted Answer

Certain lipids and proteins are preferentially localized to either the inner or outer leaflet of the bilayer.

Question 16

Which of the following best describes the function of glycolipids in the plasma membrane?

Accepted Answer

They play a role in cell-cell recognition and are found on the extracellular surface.

Question 17

Which of the following is a property of ion channels that distinguishes them from transporters?

Accepted Answer

Ion channels are not saturable and allow rapid movement of ions down their electrochemical gradient.

Question 18

Which of the following best explains why trans fatty acids are associated with increased cardiovascular disease risk?

Accepted Answer

Trans fatty acids resemble saturated fatty acids, allowing tight packing and raising LDL cholesterol.

Question 19

Which of the following best describes the process of facilitated diffusion?

Accepted Answer

It involves the movement of molecules down their concentration gradient via a specific carrier protein, without energy input.

Biological Membranes: Structure and Function – Biochemistry Study Guide

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