Question 1

Which of the following best describes the 'fluid' aspect of the fluid mosaic model of biological membranes?

Accepted Answer

The lateral and rotational movement of phospholipids within the bilayer.

Question 2

Which class of membrane lipids is most abundant in eukaryotic cell membranes?

Accepted Answer

Phospholipids

Question 3

A researcher observes that a membrane is more fluid at lower temperatures than expected. Which adaptation most likely explains this observation in a poikilothermic organism?

Accepted Answer

Increased proportion of unsaturated fatty acids due to desaturase activity

Question 4

Which of the following statements about cholesterol in animal cell membranes is TRUE?

Accepted Answer

Cholesterol acts as a fluidity buffer, preventing drastic changes in membrane fluidity.

Question 5

Which experimental evidence supports the idea that membrane proteins are mobile within the lipid bilayer?

Accepted Answer

The Frye and Edidin cell fusion experiment showing intermixing of fluorescently labeled proteins.

Question 6

Which enzyme is responsible for catalyzing the flip-flop movement of phospholipids between membrane leaflets?

Accepted Answer

Flippase

Question 7

A membrane protein is found to span the lipid bilayer multiple times, forming a pore. Which structural feature is most likely present in this protein?

Accepted Answer

Multiple transmembrane segments arranged as a beta barrel

Question 8

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

Accepted Answer

Their double bonds introduce kinks, preventing tight packing of fatty acid chains.

Question 9

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

Accepted Answer

Serving as antigens for cell recognition

Question 10

A patient is found to have a deficiency in omega-3 fatty acids. Which of the following is a likely consequence?

Accepted Answer

Impaired normal human development

Question 11

Which of the following best describes membrane asymmetry?

Accepted Answer

Unequal distribution of lipids and degree of fatty acid saturation between the two monolayers

Question 12

Which type of membrane protein is most easily removed from the membrane by changing pH or ionic strength?

Accepted Answer

Peripheral membrane proteins

Question 13

Which of the following is TRUE regarding the movement of phospholipids in the membrane?

Accepted Answer

Lateral diffusion and rotation within the monolayer are rapid and random.

Question 14

Which of the following best explains the role of cholesterol as a 'fluidity buffer' in animal cell membranes?

Accepted Answer

Cholesterol prevents drastic changes in membrane fluidity by both restricting movement at high temperatures and preventing tight packing at low temperatures.

Question 15

Which of the following is a consequence of increased cholesterol content in a membrane?

Accepted Answer

Decreased tendency of the membrane to gel upon cooling

Question 16

Which of the following is TRUE about glycoproteins in the plasma membrane?

Accepted Answer

They play a role in cell-cell recognition.

Question 17

A scientist is studying a membrane protein that is covalently attached to a fatty acid embedded in the bilayer. Which class of membrane protein does this describe?

Accepted Answer

Lipid-anchored protein

Question 18

Which of the following is a correct description of the structure of a phospholipid?

Accepted Answer

A glycerol backbone, two fatty acids, a phosphate group, and a charged head group

Question 19

Which of the following best explains why detergents can disrupt biological membranes?

Accepted Answer

Detergents are amphipathic molecules that form micelles, incorporating lipids and proteins and disrupting the bilayer.

Question 20

A mutation in the gene encoding scramblase would most directly affect which process in the cell?

Accepted Answer

Random transfer of phospholipids between membrane leaflets in the smooth ER

Cell Membranes: Structure, Composition, and Function

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