Question 1

Which of the following best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

A dynamic structure where proteins bob in a fluid phospholipid bilayer, with carbohydrates attached to the exterior.

Question 2

What is the primary function of cholesterol in animal cell membranes at moderate temperatures?

Accepted Answer

To restrain the movement of phospholipids, reducing membrane fluidity.

Question 3

A freshwater Paramecium lives in a hypotonic environment. Which adaptation allows it to survive?

Accepted Answer

A contractile vacuole that expels excess water.

Question 4

Which of the following molecules would most easily pass through a pure phospholipid bilayer without the help of a transport protein?

Accepted Answer

Oxygen ($$O_2)$$

Question 5

What is the main difference between channel proteins and carrier proteins in facilitated diffusion?

Accepted Answer

Channel proteins provide a hydrophilic tunnel, while carrier proteins change shape to move molecules.

Question 6

A red blood cell is placed in a solution and swells until it bursts. What can you conclude about the solution?

Accepted Answer

It is hypotonic to the cell.

Question 7

Which process requires energy input from ATP to move substances across the plasma membrane?

Accepted Answer

Active transport

Question 8

In the sodium-potassium pump, which of the following occurs?

Accepted Answer

$$3$$ $$Na^+$$ ions are pumped out and $$2$$ $$K^+$$ ions are pumped in, using ATP.

Question 9

Which of the following best explains why plant cells become turgid in a hypotonic solution?

Accepted Answer

Water enters the cell, and the cell wall exerts turgor pressure to prevent bursting.

Question 10

Which of the following is a function of membrane proteins?

Accepted Answer

Facilitating cell-cell recognition

Question 11

A patient with familial hypercholesterolemia has high blood cholesterol because:

Accepted Answer

Their cells lack LDL receptor proteins for receptor-mediated endocytosis.

Question 12

Which of the following statements about osmosis is correct?

Accepted Answer

Water moves from a region of lower solute concentration to higher solute concentration.

Question 13

Which of the following is an example of bulk transport?

Accepted Answer

Exocytosis of insulin from pancreatic cells

Question 14

Which adaptation would you expect to find in the cell membranes of fish living in extremely cold environments?

Accepted Answer

A high proportion of unsaturated fatty acids in membrane phospholipids

Question 15

Which of the following best describes cotransport?

Accepted Answer

The active transport of one solute directly coupled to the passive transport of another.

Question 16

Which of the following is true about the sidedness (asymmetry) of biological membranes?

Accepted Answer

The inside and outside faces of the membrane have distinct protein, lipid, and carbohydrate compositions.

Question 17

Which of the following is a real-life medical application of membrane protein function?

Accepted Answer

Blocking the CCR5 coreceptor to prevent HIV entry into immune cells.

Question 18

Which of the following best explains why glucose carrier proteins do not transport fructose?

Accepted Answer

Carrier proteins are specific to the shape of the molecule they transport.

Question 19

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

Accepted Answer

Synthesis of DNA

Question 20

A plant cell is placed in a hypertonic solution. What will happen to the cell?

Accepted Answer

It will undergo plasmolysis.

Membrane Structure and Function: Study Notes for General Biology

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