Q: A cell uses the sodium-potassium pump to maintain ion gradients. Which equation best describes the stoichiometry of this pump?

$ 3 \text{Na}^+ \text{ out}, 2 \text{K}^+ \text{ in} $

Question 1

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

Accepted Answer

A dynamic structure with proteins floating in or on a fluid phospholipid bilayer.

Question 2

Which component of the plasma membrane is primarily responsible for its selective permeability?

Accepted Answer

Phospholipid bilayer

Question 3

A red blood cell is placed in a hypotonic solution. Which process will occur, and what is the likely outcome?

Accepted Answer

Osmosis; water will move into the cell, causing it to swell and possibly burst.

Question 4

Which of the following is an example of facilitated diffusion?

Accepted Answer

Glucose entering a muscle cell via a specific transport protein.

Question 5

Which equation best represents the net movement of water during osmosis?

Accepted Answer

$ \Psi = \Psi_s + \Psi_p $ where water moves from higher to lower water potential

Question 6

Which of the following statements about active transport is correct?

Accepted Answer

Active transport requires ATP to move substances against their concentration gradient.

Question 7

A cell uses the sodium-potassium pump to maintain ion gradients. Which equation best describes the stoichiometry of this pump?

Accepted Answer

$ 3 	ext{Na}^+ 	ext{ out}, 2 	ext{K}^+ 	ext{ in} $

Question 8

Which process allows a white blood cell to engulf a bacterium?

Accepted Answer

Phagocytosis

Question 9

Which of the following best explains why small nonpolar molecules can cross the plasma membrane easily?

Accepted Answer

They dissolve in the hydrophobic core of the phospholipid bilayer.

Question 10

A cell is placed in a solution with a higher solute concentration than the cytoplasm. What will happen to the cell?

Accepted Answer

Water will move out of the cell, causing it to shrink.

Question 11

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

Accepted Answer

Synthesizing phospholipids

Question 12

Which mechanism is used by cells to secrete large molecules, such as hormones, out of the cell?

Accepted Answer

Exocytosis

Question 13

Which of the following best describes the role of cholesterol in the plasma membrane?

Accepted Answer

It stabilizes membrane fluidity at different temperatures.

Question 14

A patient is given an intravenous solution that is hypertonic to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

The cells will shrink as water leaves the cells.

Question 15

Which of the following is true about receptor-mediated endocytosis?

Accepted Answer

It involves the selective uptake of specific molecules bound to receptors.

Question 16

Which of the following best explains why ions such as Na	extsuperscript{+} and K	extsuperscript{+} require transport proteins to cross the plasma membrane?

Accepted Answer

They are hydrophilic and cannot pass through the hydrophobic core.

Question 17

Which of the following scenarios best illustrates the concept of selective permeability?

Accepted Answer

A cell membrane allows glucose but not sodium ions to enter the cell.

Question 18

Which of the following equations correctly represents the energy requirement for active transport?

Accepted Answer

$ \Delta G > 0 $

Question 19

Which process is responsible for the uptake of liquid droplets by a cell?

Accepted Answer

Pinocytosis

Question 20

A cell is placed in an isotonic solution. Which of the following best describes the net movement of water?

Accepted Answer

There is no net movement of water.

Cell Membrane Structure and Transport Mechanisms

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