Q: Which equation best represents the action of the sodium-potassium pump?

$$3\ \text{Na}^+_{\text{in}} + 2\ \text{K}^+_{\text{out}} + \text{ATP} \rightarrow 3\ \text{Na}^+_{\text{out}} + 2\ \text{K}^+_{\text{in}} + \text{ADP} + \text{P}_i$$

Question 1

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

Accepted Answer

A dynamic bilayer of phospholipids with proteins embedded or attached, allowing lateral movement of components.

Question 2

Phospholipids are described as amphipathic molecules. What does 'amphipathic' mean in this context?

Accepted Answer

They contain both hydrophilic and hydrophobic regions.

Question 3

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membranes must be fluid to function properly, and cholesterol helps maintain fluidity at varying temperatures.

Question 4

At warm temperatures (such as 37°C), what is the effect of cholesterol on the plasma membrane?

Accepted Answer

It restrains the movement of phospholipids, reducing membrane fluidity.

Question 5

Which type of membrane protein penetrates the hydrophobic core of the lipid bilayer and often spans the entire membrane?

Accepted Answer

Transmembrane proteins

Question 6

Cell-surface carbohydrates play a crucial role in cell-cell recognition. Which of the following is a real-world example of this process?

Accepted Answer

HIV binding to immune cell-surface proteins CD4 and CCR5 to infect cells.

Question 7

Which of the following molecules can cross the plasma membrane most easily without the help of transport proteins?

Accepted Answer

Hydrophobic molecules

Question 8

Aquaporins are a type of channel protein. What is their primary function?

Accepted Answer

Facilitate the diffusion of water molecules across the membrane.

Question 9

Which of the following best describes facilitated diffusion?

Accepted Answer

Passive movement of molecules down their concentration gradient with the help of transport proteins.

Question 10

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

Accepted Answer

It will gain water and swell, possibly lysing.

Question 11

Which equation correctly represents the movement of water during osmosis?

Accepted Answer

Water moves from a region of lower solute concentration to higher solute concentration: $$	ext{Low solute} ightarrow 	ext{High solute}$$

Question 12

Which of the following is NOT a function carried out by membrane proteins?

Accepted Answer

DNA replication

Question 13

The sodium-potassium pump is an example of which type of transport?

Accepted Answer

Active transport

Question 14

Which equation best represents the action of the sodium-potassium pump?

Accepted Answer

$$3\ 	ext{Na}^+_{	ext{in}} + 2\ 	ext{K}^+_{	ext{out}} + 	ext{ATP} ightarrow 3\ 	ext{Na}^+_{	ext{out}} + 2\ 	ext{K}^+_{	ext{in}} + 	ext{ADP} + 	ext{P}_i$$

Question 15

Which of the following best describes the electrochemical gradient?

Accepted Answer

The combined effect of an ion's concentration gradient and the membrane potential.

Question 16

Which type of transport requires energy and moves substances against their concentration gradient?

Accepted Answer

Active transport

Question 17

Which process allows large molecules, such as proteins, to cross the plasma membrane in bulk via vesicles?

Accepted Answer

Bulk transport

Question 18

During receptor-mediated endocytosis, what triggers the formation of a vesicle?

Accepted Answer

Binding of specific solutes to receptors on the plasma membrane.

Question 19

Which of the following is a major electrogenic pump in plant, fungi, and bacterial cells?

Accepted Answer

Proton pump

Question 20

A cell is placed in a hypertonic solution. Predict what will happen to a plant cell and explain why.

Accepted Answer

It will become plasmolyzed because water leaves the cell.

Chapter 7: Membranes – Structure and Function

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