Question 1

Which of the following molecules is most likely to diffuse directly through a pure lipid bilayer without the aid of a transport protein?

Accepted Answer

O2

Question 2

A patient is diagnosed with a genetic defect that prevents the formation of aquaporins in kidney cells. Which process would be most directly affected?

Accepted Answer

Osmosis of water

Question 3

Which of the following best explains why the rate of facilitated diffusion plateaus at high solute concentrations, as shown in the provided graph?

Accepted Answer

All available transport proteins are saturated with solute.

Question 4

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It moves 3 Na+ out of the cell and 2 K+ into the cell per ATP hydrolyzed.

Question 5

A nerve cell is exposed to tetrodotoxin, which blocks voltage-gated Na+ channels. What is the most immediate effect on the action potential?

Accepted Answer

The action potential will fail to propagate along the axon.

Question 6

Which of the following best describes the driving force for the movement of Na+ into a neuron during the rising phase of an action potential?

Accepted Answer

The electrochemical gradient for Na+

Question 7

Which of the following is a key difference between channel proteins and transporter proteins in the cell membrane?

Accepted Answer

Channels allow rapid movement of ions without conformational change, while transporters undergo conformational changes to move solutes.

Question 8

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

Accepted Answer

Water will enter the cell by osmosis, driven by the solute concentration gradient.

Question 9

Which of the following best describes secondary active transport?

Accepted Answer

It couples the uphill transport of one solute to the downhill movement of another.

Question 10

The glucose-Na+ symporter in intestinal epithelial cells is an example of:

Accepted Answer

Symport secondary active transport

Question 11

Which of the following equations best represents the relationship between the rate of simple diffusion ($$v) $$and the solute concentration gradient ($$\Delta[S]$$)?

Accepted Answer

$$v = k \cdot \Delta[S]$$

Question 12

Which of the following best explains why facilitated diffusion of glucose through GluT transporters is saturable?

Accepted Answer

There are a limited number of transporter proteins, each with a maximum rate.

Question 13

Which of the following scenarios would most likely result in the fastest rate of ion movement across a membrane?

Accepted Answer

Movement of Na+ through a specific ion channel

Question 14

A cell is placed in a solution containing a high concentration of K+ and a low concentration of Na+. The membrane is only permeable to K+. What will happen to the membrane potential?

Accepted Answer

It will become more negative inside the cell.

Question 15

Which of the following is true regarding the selectivity of ion channels?

Accepted Answer

Ion channels have selectivity filters that allow only specific ions to pass.

Question 16

Which of the following best describes the function of the Na+/K+ pump in maintaining the resting membrane potential?

Accepted Answer

It creates and maintains a high concentration of Na+ outside and K+ inside the cell.

Question 17

Which of the following is a real-life example of a disease caused by a defect in a membrane transporter?

Accepted Answer

Cystic fibrosis, caused by a defective Cl- channel

Question 18

Which of the following statements about the movement of water across cell membranes is correct?

Accepted Answer

Water moves by osmosis, which is a type of passive transport.

Question 19

Which of the following best describes the role of the electrochemical gradient in the movement of ions across membranes?

Accepted Answer

It is the combined effect of the ion's concentration gradient and the membrane potential.

Transport Across Cell Membranes: Principles and Mechanisms

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