Question 1

Which of the following best describes the structure of biological membranes according to the fluid mosaic model proposed by Singer and Nicolson?

Accepted Answer

A fluid phospholipid bilayer with a mosaic of embedded proteins that can move laterally.

Question 2

Which component of the cell membrane is primarily responsible for its permeability barrier function?

Accepted Answer

Phospholipid bilayer

Question 3

Sterols such as cholesterol are important for membrane fluidity in animal cells. Which analogous compound is found in some bacterial membranes?

Accepted Answer

Hopanoids

Question 4

A cell is exposed to cold temperatures. Which modification would help maintain membrane fluidity?

Accepted Answer

Increase the proportion of unsaturated fatty acids in membrane lipids.

Question 5

Which equation best represents the relationship between the melting point ($$T_m) of a $$membrane and the number of double bonds ($$n) in $$its fatty acid chains?

Accepted Answer

$$T_m = T_0$ - k n$$

Question 6

Which of the following statements about membrane protein mobility is correct?

Accepted Answer

Most membrane proteins can move laterally within the membrane unless anchored.

Question 7

Which type of membrane protein is characterized by hydrophilic regions that remain on the membrane surface and are attached to polar head groups by ionic and hydrogen bonding?

Accepted Answer

Peripheral membrane proteins

Question 8

A mutation causes a cell to lack flippase enzymes. What is the most likely consequence?

Accepted Answer

Transverse diffusion of phospholipids will be severely reduced.

Question 9

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

Accepted Answer

Their cis double bonds create kinks, preventing tight packing.

Question 10

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

Accepted Answer

Serving as recognition markers for cell-cell communication.

Question 11

Which of the following membrane lipids is NOT commonly found in the membranes of most bacteria?

Accepted Answer

Cholesterol

Question 12

Which process is catalyzed by phospholipid translocators (flippases) in the cell membrane?

Accepted Answer

Transverse diffusion (flip-flop) of phospholipids between monolayers.

Question 13

Which of the following best describes the asymmetric distribution of lipids in biological membranes?

Accepted Answer

The two sides of the membrane are structurally and functionally dissimilar.

Question 14

Which membrane protein type is covalently linked to the membrane by lipid anchors embedded in the lipid bilayer?

Accepted Answer

Lipid-anchored proteins

Question 15

A patient is diagnosed with a genetic disorder affecting the carbohydrate side chains of glycoproteins. Which cellular process is most likely to be impaired?

Accepted Answer

Cell-cell recognition and communication

Question 16

Which of the following is a real-world consequence of decreased membrane fluidity in nerve cells?

Accepted Answer

Impaired function of ion channels and slower nerve impulse transmission

Question 17

Which of the following best describes the role of lipid rafts in cell membranes?

Accepted Answer

They are microdomains involved in cell signaling and protein interactions.

Question 18

Which of the following equations best describes the effect of fatty acid chain length ($$L) on $$the melting point ($$T_m) of $$membrane lipids?

Accepted Answer

$$T_m = T_0$ + k L$$

Question 19

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

Accepted Answer

Forming the permeability barrier

Ch 7 - Membranes: Structure, Function, and Chemistry

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