Question 1

Which of the following best describes the 'fluid mosaic model' of the cell membrane?

Accepted Answer

A flexible structure where proteins and lipids can move laterally within the bilayer.

Question 2

What property of phospholipids is primarily responsible for the formation of the bilayer structure in cell membranes?

Accepted Answer

Their amphipathic nature, having both hydrophilic heads and hydrophobic tails.

Question 3

A scientist cools a sample of cell membranes and observes that the membrane becomes less fluid and more rigid. Which change in phospholipid composition would help restore membrane fluidity at low temperatures?

Accepted Answer

Increasing the proportion of unsaturated fatty acids.

Question 4

Which of the following best explains why the cell membrane is described as 'selectively permeable'?

Accepted Answer

It allows some substances to cross more easily than others.

Question 5

A patient is exposed to a snake venom containing phospholipases. What is the most likely effect on their cell membranes?

Accepted Answer

The membranes become leaky, causing loss of cell contents.

Question 6

Which of the following is a function of recognition proteins in the cell membrane?

Accepted Answer

Identifying the cell to other cells and the immune system.

Question 7

Why do unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their double bonds introduce kinks, preventing tight packing.

Question 8

Which of the following molecules is most likely to diffuse directly through the phospholipid bilayer without the help of a transport protein?

Accepted Answer

A small nonpolar molecule such as $ \mathrm{O}_2 $ (oxygen).

Question 9

A vesicle from the Golgi apparatus fuses with the plasma membrane to release its contents outside the cell. Which property of the membrane allows this process to occur?

Accepted Answer

The fluidity and flexibility of the membrane.

Question 10

Which of the following best describes the arrangement of phospholipids in the cell membrane?

Accepted Answer

Hydrophilic heads face outward toward the aqueous environment, while hydrophobic tails face inward.

Question 11

A mutation causes a cell to produce membrane phospholipids with only saturated fatty acids. What is the most likely consequence for the cell at low temperatures?

Accepted Answer

The membrane will become too rigid and may crack.

Question 12

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

Accepted Answer

Storing genetic information.

Question 13

If a cell membrane lost its selective permeability, which of the following would most likely occur?

Accepted Answer

The cell would lose control over what enters and leaves, potentially leading to cell death.

Question 14

Which equation best represents the relationship between temperature and the kinetic energy of membrane molecules?

Accepted Answer

$ KE = \frac{3}{2} k_B T $

Question 15

Which of the following best explains why cholesterol is important in animal cell membranes?

Accepted Answer

It helps maintain membrane fluidity across temperature changes.

Question 16

A cell is placed in a solution containing a high concentration of a small, nonpolar molecule. Which process will most likely allow this molecule to enter the cell?

Accepted Answer

Simple diffusion through the phospholipid bilayer.

Question 17

Which of the following statements about the movement of proteins within the cell membrane is correct?

Accepted Answer

Proteins can move laterally within the lipid bilayer.

Question 18

Which of the following best describes the effect of temperature on membrane fluidity?

Accepted Answer

Increasing temperature increases membrane fluidity.

Question 19

Which of the following is a real-world example of the importance of membrane fluidity?

Accepted Answer

Red blood cells becoming rigid in cold temperatures, leading to impaired circulation.

Structure and Function of the Cell Membrane

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