Question 1

Which of the following molecules would diffuse most rapidly across a protein-free, artificial lipid bilayer, as shown in the first image?

Accepted Answer

A small nonpolar molecule such as $$O_2$$

Question 2

Based on the second image, what is the primary function of membrane transport proteins in a cell membrane?

Accepted Answer

To provide selective passageways for specific molecules and ions across the membrane

Question 3

According to the third image, which of the following statements best explains why ions such as $$K^+$$ and $$Na^+$$ cannot diffuse freely across an artificial lipid bilayer?

Accepted Answer

Ions are charged and the hydrophobic core of the bilayer is impermeable to charged molecules

Question 4

Referencing the fourth image (ion concentration table), which of the following best describes the distribution of $$Na^+$$ and $$K^+$$ ions in a typical mammalian cell?

Accepted Answer

$$Na^+ is $$higher outside the cell, $$K^+ is $$higher inside the cell

Question 5

Which of the following best distinguishes a channel from a transporter, as shown in the fifth image?

Accepted Answer

A channel forms a hydrophilic pore for ions to pass through, while a transporter binds solutes and undergoes conformational changes

Question 6

Based on the sixth image, which of the following statements about passive and active transport is correct?

Accepted Answer

Passive transport moves molecules down their concentration gradient, while active transport moves molecules against their concentration gradient using energy

Question 7

A protozoan living in a hypotonic environment uses a contractile vacuole to expel water, as shown in the seventh image. What is the driving force for water entry into the cell?

Accepted Answer

Osmosis due to higher osmolarity of solutes inside the cell

Question 8

Which of the following best explains the role of aquaporins, as shown in the ninth and tenth images?

Accepted Answer

Aquaporins facilitate the rapid and selective passage of water molecules across the plasma membrane

Question 9

Which of the following is a correct statement about the Na$$^+/K$^+$$ ATPase pump, as shown in the sixteenth and seventeenth images?

Accepted Answer

It uses ATP hydrolysis to pump 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell

Question 10

A cell is placed in a solution with a higher concentration of glucose than inside the cell. Which type of transporter would be responsible for the passive movement of glucose into the cell, as shown in the thirteenth image?

Accepted Answer

A glucose uniport transporter

Question 11

Which of the following best describes the function of a symport, as shown in the nineteenth image?

Accepted Answer

It couples the transport of two solutes in the same direction across the membrane

Question 12

In the context of the gut epithelium (twentieth and twenty-first images), how do epithelial cells achieve the net uptake of glucose from the gut lumen?

Accepted Answer

By using a Na$$^+-$$glucose symport to actively transport glucose into the cell, even against its concentration gradient

Question 13

Which of the following statements about ion channels is correct, as shown in the twenty-third and twenty-fourth images?

Accepted Answer

Ion channels are selective for specific ions and can be gated by various stimuli

Question 14

The selectivity of a K$$^+$$ channel, as shown in the twenty-sixth and twenty-seventh images, is primarily due to which of the following?

Accepted Answer

The precise fit of the selectivity filter for dehydrated K$$^+$$ ions

Question 15

Which of the following best explains how the resting membrane potential is established in animal cells, as shown in the thirty-fourth and thirty-fifth images?

Accepted Answer

K$$^+$$ leak channels allow K$$^+ to $$move out of the cell, leaving behind unbalanced negative charges

Question 16

Patch-clamp recording, as shown in the thirty-sixth and thirty-seventh images, is used to:

Accepted Answer

Measure the electrical current passing through a single ion channel

Question 17

Which of the following types of ion channels would open in response to a change in membrane potential, as shown in the forty-first image?

Accepted Answer

Voltage-gated ion channel

Question 18

Mechanically-gated ion channels, as shown in the forty-third image, play a crucial role in which physiological process?

Accepted Answer

Hearing, by allowing ions to flow into auditory hair cells in response to sound vibrations

Membrane Transport Proteins and Ion Channels: Structure, Function, and Genetic Relevance

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