Question 1

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

Accepted Answer

A double layer of lipids with proteins embedded and able to move laterally, creating a dynamic and heterogeneous structure.

Question 2

Which of the following factors would most likely increase the fluidity of a cell membrane at physiological temperature?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in membrane phospholipids.

Question 3

A researcher is studying a membrane protein that can only be extracted from the membrane by dissolving the lipid bilayer with detergent. This protein is most likely:

Accepted Answer

An integral membrane protein

Question 4

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

Accepted Answer

Cholesterol decreases membrane permeability to ions and small polar molecules.

Question 5

A mutation causes a cell to lack flippase enzymes. Which process would be most directly affected?

Accepted Answer

Transverse diffusion (flip-flop) of phospholipids between monolayers

Question 6

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

Accepted Answer

Their double bonds introduce kinks, preventing phospholipids from packing closely together.

Question 7

A cell is exposed to a sudden drop in temperature. Which adaptation would help maintain membrane fluidity?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in membrane phospholipids.

Question 8

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

Accepted Answer

Mediating cell-cell recognition and communication.

Question 9

A patient has a genetic disorder affecting the glycosylation of membrane proteins. Which of the following symptoms would most likely be observed?

Accepted Answer

Impaired cell-cell recognition and immune response.

Question 10

Which of the following best describes the orientation of membrane proteins in the lipid bilayer?

Accepted Answer

Membrane proteins are asymmetrically oriented and maintain a fixed orientation once inserted.

Question 11

Which of the following is a characteristic of peripheral membrane proteins?

Accepted Answer

They are bound to membrane surfaces through weak electrostatic interactions and hydrogen bonds.

Question 12

A scientist uses freeze-fracture electron microscopy to study a cell membrane. What would they most likely observe?

Accepted Answer

Particles corresponding to membrane proteins embedded within the lipid bilayer.

Question 13

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

Accepted Answer

Cholesterol increases membrane fluidity at low temperatures and decreases it at high temperatures.

Question 14

Which of the following is TRUE regarding the movement of phospholipids in biological membranes?

Accepted Answer

Lateral diffusion within a monolayer is rapid and common.

Question 15

Which of the following best describes the role of membrane proteins in signal transduction?

Accepted Answer

They serve as receptors that bind external chemical signals and initiate cellular responses.

Question 16

A red blood cell has the B blood group antigen. Which carbohydrate is present on the glycolipid of its plasma membrane?

Accepted Answer

Galactose (Gal)

Question 17

Which of the following equations correctly represents the relationship between the rate of facilitated diffusion ($$v$$), maximum rate ($$V_{max}$$), substrate concentration ($$[S]$$), and Michaelis constant ($$K_m) as $$shown in a Lineweaver-Burk plot?

Accepted Answer

$$\frac{1}{v} = \frac{K_m}{V_{max}} \cdot \frac{1}{[S]} + \frac{1}{V_{max}}$$

Question 18

Which of the following is a real-life example of the importance of membrane asymmetry?

Accepted Answer

The localization of most glycolipids to the outer leaflet of the plasma membrane for cell recognition.

Question 19

A cell is exposed to a toxin that disrupts hydrogen bonding and electrostatic interactions. Which class of membrane proteins would be most easily released from the membrane?

Accepted Answer

Peripheral membrane proteins

Question 20

Which of the following best explains why poikilothermic organisms (such as fish) alter the fatty acid composition of their membranes in response to temperature changes?

Accepted Answer

To maintain constant membrane fluidity despite changes in environmental temperature.

Cell Membranes: Structure, Function, and Chemistry

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