Q: Which equation best represents the rate of simple diffusion across a cell membrane?

$$J = P \times A \times (C_1$ - C_2$)$$

Question 1

Which of the following best describes the difference between osmolarity and tonicity?

Accepted Answer

Osmolarity is the total solute concentration (penetrating and non-penetrating), while tonicity describes the effect of non-penetrating solutes on cell volume.

Question 2

A red blood cell is placed in a solution containing 300 mOsm/L of urea (a penetrating solute) and 150 mOsm/L of NaCl (a non-penetrating solute). What will happen to the cell?

Accepted Answer

The cell will swell because urea will enter the cell, and water will follow.

Question 3

Which equation best represents the rate of simple diffusion across a cell membrane?

Accepted Answer

$$J = P 	imes A 	imes (C_1$ - C_2$)$$

Question 4

Which property of channel proteins determines their selectivity for specific ions?

Accepted Answer

The size of the pore and the charge of amino acids lining the pore.

Question 5

A patient is given a drug that blocks Na+/K+ ATPase activity. What is the most likely immediate effect on the cell?

Accepted Answer

The cell will lose its ability to maintain a sodium gradient, leading to depolarization.

Question 6

Which of the following is TRUE about facilitated diffusion?

Accepted Answer

It uses carrier or channel proteins to move molecules down their concentration gradient.

Question 7

Which type of vesicular transport is responsible for the uptake of extracellular fluid and is non-selective?

Accepted Answer

Pinocytosis

Question 8

A cell uses secondary active transport to import glucose. Which of the following best describes this process?

Accepted Answer

Glucose is moved against its concentration gradient using the energy stored in the Na+ gradient.

Question 9

Which of the following statements about carrier proteins is CORRECT?

Accepted Answer

Carrier proteins change conformation to transport molecules across the membrane.

Question 10

If a cell is exposed to a solution containing only penetrating solutes, what will happen to its volume?

Accepted Answer

The cell volume will not change because penetrating solutes equilibrate across the membrane.

Question 11

Which of the following is an example of primary active transport?

Accepted Answer

Na+/K+ ATPase pumping Na+ out and K+ in using ATP.

Question 12

Which of the following best explains why non-penetrating solutes determine tonicity?

Accepted Answer

Non-penetrating solutes cannot cross the membrane, so they cause water to move in or out of the cell.

Question 13

Which of the following is TRUE about saturation in carrier-mediated transport?

Accepted Answer

Transport rate reaches a maximum when all carriers are occupied.

Question 14

A cell is placed in a solution with a higher concentration of non-penetrating solutes than inside the cell. What is the expected outcome?

Accepted Answer

The cell will shrink.

Question 15

Which of the following is a feature of channel proteins but NOT carrier proteins?

Accepted Answer

They allow rapid movement of ions across the membrane.

Question 16

Which process requires ATP and is used to move large molecules out of the cell?

Accepted Answer

Exocytosis

Question 17

A competitive inhibitor is added to a solution containing a carrier protein and its substrate. What is the expected effect?

Accepted Answer

Transport rate will decrease due to competition for the binding site.

Question 18

Which of the following is TRUE about secondary active transport?

Accepted Answer

It uses the energy stored in an ion gradient to move another molecule against its gradient.

Question 19

Which equation best describes the saturation kinetics of carrier-mediated transport?

Accepted Answer

$$v = \frac{V_{max} 	imes [S]}{K_m + [S]}$$

Question 20

Which of the following is a characteristic of facilitated diffusion but NOT simple diffusion?

Accepted Answer

It requires a membrane protein for transport.

Cell Membrane Transport: Mechanisms and Principles

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