Q: Which of the following equations best represents the electrochemical gradient for an ion across a membrane?

$$ \Delta G = RT \ln \left( \frac{[C]_\text{in}}{[C]_\text{out}} \right) + zF\Delta \Psi $$

Question 1

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

Accepted Answer

A dynamic bilayer of amphipathic phospholipids with proteins and other molecules embedded and able to move laterally.

Question 2

What is the primary function of cholesterol in animal cell membranes at moderate temperatures (such as 37°C)?

Accepted Answer

It prevents the membrane from becoming too fluid by restraining phospholipid movement.

Question 3

A red blood cell is placed in a solution and swells until it bursts. Which of the following best describes the tonicity of the solution relative to the cell, and the direction of water movement?

Accepted Answer

The solution is hypotonic; water moves into the cell.

Question 4

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

Accepted Answer

Oxygen ($O_2$)

Question 5

Which statement correctly distinguishes between channel proteins and carrier proteins in facilitated diffusion?

Accepted Answer

Channel proteins provide a hydrophilic pathway for molecules to pass, while carrier proteins undergo conformational changes to transport molecules.

Question 6

A plant cell is placed in a hypertonic solution. What is the most likely outcome for the cell?

Accepted Answer

The cell will undergo plasmolysis as the plasma membrane pulls away from the cell wall.

Question 7

Which of the following best explains why membranes rich in unsaturated fatty acids remain more fluid at lower temperatures?

Accepted Answer

Unsaturated fatty acids have kinks in their tails, preventing tight packing.

Question 8

Which of the following is an example of active transport across a cell membrane?

Accepted Answer

Movement of $Na^+$ ions from low to high concentration using the sodium-potassium pump and ATP.

Question 9

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

The cell selectively takes in specific molecules that bind to receptors on the membrane, forming coated vesicles.

Question 10

Familial hypercholesterolemia is caused by a defect in which of the following processes?

Accepted Answer

Defective LDL receptor proteins impairing receptor-mediated endocytosis of cholesterol.

Question 11

Which of the following equations best represents the electrochemical gradient for an ion across a membrane?

Accepted Answer

$$ \Delta G = RT \ln \left( \frac{[C]_	ext{in}}{[C]_	ext{out}} ight) + zF\Delta \Psi $$

Question 12

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

Accepted Answer

Synthesizing phospholipids for the membrane.

Question 13

A glucose molecule is transported into an intestinal epithelial cell against its concentration gradient, coupled with the movement of $Na^+$ down its gradient. What type of transport is this?

Accepted Answer

Cotransport (secondary active transport)

Question 14

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the diffusion of free water molecules across a selectively permeable membrane toward higher solute concentration.

Question 15

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

Accepted Answer

Water enters the cell, and the cell wall prevents excessive expansion, resulting in turgor pressure.

Question 16

Which of the following is a property of integral membrane proteins?

Accepted Answer

They penetrate the hydrophobic core of the lipid bilayer.

Question 17

Which of the following best describes the role of membrane carbohydrates?

Accepted Answer

They function as markers for cell recognition and communication.

Question 18

Which of the following statements about bulk transport is correct?

Accepted Answer

Bulk transport requires vesicle formation and is used for large molecules such as proteins and polysaccharides.

Question 19

Which of the following best explains why the sodium-potassium pump is considered electrogenic?

Accepted Answer

It generates a net movement of positive charge out of the cell, creating a voltage difference across the membrane.

Question 20

Which of the following is true regarding the sidedness of membranes?

Accepted Answer

Membranes have distinct inside and outside faces with different compositions.

Ch. 7 Membrane Structure and Function (Chapter 7) – Study Notes

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