Question 1

Which of the following best describes the structure of a phospholipid in the plasma membrane?

Accepted Answer

A molecule with a hydrophilic head and two hydrophobic fatty acid tails

Question 2

What is the primary function of phospholipids in the plasma membrane?

Accepted Answer

To form a selectively permeable barrier that separates the cell from its environment

Question 3

If all phospholipids in a plant cell membrane were saturated, what would most likely happen to the membrane in cold environments?

Accepted Answer

The membrane would become less fluid and more rigid, impairing function

Question 4

Why do unsaturated fatty acid tails in phospholipids help maintain membrane fluidity at low temperatures?

Accepted Answer

The kinks in unsaturated tails prevent tight packing of phospholipids

Question 5

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

Accepted Answer

Storing genetic information

Question 6

A channel protein in the plasma membrane is most likely to be involved in which process?

Accepted Answer

Facilitated diffusion of ions or water

Question 7

Which property of a protein allows it to function as a receptor in the plasma membrane?

Accepted Answer

Its specific three-dimensional shape allows binding to signaling molecules

Question 8

Which equation best represents the relationship between membrane fluidity (F), temperature (T), and the degree of unsaturation (U) of phospholipid tails?

Accepted Answer

$$F \propto T 	imes U$$

Question 9

A plant in a cold environment is found to have a high proportion of unsaturated phospholipids in its plasma membrane. What is the most likely advantage of this adaptation?

Accepted Answer

It maintains membrane fluidity, allowing proper function at low temperatures

Question 10

Which of the following best explains why integral membrane proteins can span the lipid bilayer?

Accepted Answer

They have hydrophobic regions that interact with the fatty acid tails of phospholipids

Question 11

A mutation causes a membrane protein to lose its specific shape. Which function is most likely to be affected?

Accepted Answer

Receptor-mediated signaling

Question 12

Which of the following scenarios best illustrates the role of a carrier protein in the plasma membrane?

Accepted Answer

Glucose is transported into a cell against its concentration gradient using ATP

Question 13

Which of the following statements about the plasma membrane is correct?

Accepted Answer

It is selectively permeable, allowing some substances to cross more easily than others

Question 14

Which of the following best describes the effect of cholesterol on membrane fluidity at low temperatures?

Accepted Answer

Cholesterol prevents the membrane from becoming too rigid by disrupting phospholipid packing

Question 15

Which of the following is a direct consequence of the amphipathic nature of phospholipids?

Accepted Answer

They spontaneously form bilayers in aqueous environments

Study Guide: Structure and Function of the Plasma Membrane

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