Question 1

Which statement best describes the fluid mosaic model of cell membranes?

Accepted Answer

Cell membranes are dynamic structures where lipids and proteins move laterally within the bilayer.

Question 2

Which of the following factors increases membrane fluidity?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in phospholipids.

Question 3

A cell membrane contains cholesterol. What is the primary effect of cholesterol on membrane fluidity at moderate temperatures?

Accepted Answer

Cholesterol decreases membrane fluidity by stabilizing the membrane.

Question 4

Which equation best describes the rate of simple diffusion across a membrane?

Accepted Answer

$$J = D \frac{\Delta C}{\Delta x}$$

Question 5

Which type of membrane protein is most likely to function as a channel for facilitated diffusion?

Accepted Answer

Integral transmembrane protein

Question 6

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

Accepted Answer

It will swell and may burst due to water influx.

Question 7

Which of the following molecules can most easily diffuse through a cell membrane without the help of a transport protein?

Accepted Answer

Oxygen ($$O_2)$$

Question 8

What is the main function of glycoproteins in the cell membrane?

Accepted Answer

Cell recognition and signaling.

Question 9

Which of the following best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

Phospholipids have hydrophilic heads and hydrophobic tails, causing them to arrange with tails inward and heads outward.

Question 10

A mutation causes a membrane protein to lose its ability to bind to carbohydrates. Which function is most likely to be affected?

Accepted Answer

Cell-cell recognition.

Question 11

Which of the following statements about selective permeability is correct?

Accepted Answer

The cell membrane allows some substances to pass while blocking others.

Question 12

Which process does NOT require energy input from the cell?

Accepted Answer

Facilitated diffusion of glucose.

Question 13

A scientist measures the rate of facilitated diffusion of a solute and finds it plateaus at high concentrations. What is the most likely explanation?

Accepted Answer

All transport proteins are occupied, reaching $$V_{max}.$$

Question 14

Which of the following changes would DECREASE the fluidity of a cell membrane?

Accepted Answer

Increasing the proportion of saturated fatty acids.

Question 15

Which of the following is a real-world example of membrane protein function?

Accepted Answer

Insulin receptor facilitating glucose uptake in muscle cells.

Question 16

If a cell membrane is composed mainly of phospholipids with short, unsaturated fatty acid tails, what property will the membrane most likely exhibit?

Accepted Answer

High fluidity and increased permeability.

Question 17

Which of the following best describes the role of membrane proteins in selective permeability?

Accepted Answer

They act as channels or carriers for specific molecules.

Question 18

A patient with cystic fibrosis has a mutation in the CFTR protein, a membrane channel. What is the direct consequence of this mutation?

Accepted Answer

Defective chloride ion transport across epithelial cell membranes.

Question 19

Which of the following is true about the orientation of membranes in eukaryotic cells?

Accepted Answer

Membrane proteins can have different orientations depending on their function.

Question 20

Which of the following best explains why facilitated diffusion is necessary for glucose transport into most animal cells?

Accepted Answer

Glucose is a large, polar molecule that cannot cross the lipid bilayer without a transport protein.

Cell Membranes: Structure, Fluidity, and Permeability

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