Question 1

Which of the following statements best describes the difference between simple diffusion and facilitated diffusion across a cell membrane?

Accepted Answer

Facilitated diffusion uses transport proteins to move solutes down their concentration gradient, while simple diffusion does not require proteins.

Question 2

A cell is placed in a hypotonic solution. What will happen to the cell, and why?

Accepted Answer

The cell will swell and may lyse because water moves into the cell toward higher solute concentration.

Question 3

Which equation describes the rate of carrier-mediated transport, and what does each variable represent?

Accepted Answer

$$v = V_{max} \frac{[S]}{K_m + [S]}$$ ; $$v is $$rate, $$V_{max} is $$maximum velocity, $$[S] is $$substrate concentration, $$K_m is $$substrate concentration at half $$V_{max}.$$

Question 4

Which of the following is a characteristic of active transport but NOT passive transport?

Accepted Answer

Intrinsic directionality and movement of solutes against their concentration gradient.

Question 5

A red blood cell is placed in a hypertonic solution. What is the expected outcome?

Accepted Answer

The cell will shrivel as water leaves the cell by osmosis.

Question 6

Which transport mechanism is responsible for the rapid passage of water molecules across cell membranes?

Accepted Answer

Aquaporins

Question 7

The Na+/K+ ATPase pump moves sodium and potassium ions across the plasma membrane. Which statement best describes its function?

Accepted Answer

It moves sodium ions out of the cell and potassium ions into the cell, using ATP hydrolysis.

Question 8

Which Nobel Prize-winning discovery is associated with the identification of water channels in cell membranes?

Accepted Answer

Discovery of aquaporins

Question 9

Which of the following best explains why glucose is rapidly taken up by animal cells even when its concentration is low outside the cell?

Accepted Answer

Glucose is phosphorylated upon entry, keeping its internal concentration low and favoring continued uptake.

Question 10

Which of the following is TRUE about the mechanism of the erythrocyte anion exchange protein?

Accepted Answer

It exchanges chloride and bicarbonate ions in a strict 1:1 ratio.

Question 11

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

Accepted Answer

They form hydrophilic pores that allow solutes to cross the membrane directly.

Question 12

Which type of transport protein is most likely to be inhibited by molecules structurally similar to its substrate?

Accepted Answer

Carrier proteins

Question 13

Which equation describes the rate of inward flux for simple diffusion?

Accepted Answer

$$v_{inward} = P \Delta[S]$$ ; $$P is $$permeability coefficient, $$\Delta[S] is $$concentration difference.

Question 14

Which of the following is a function of ion channels in animal cells?

Accepted Answer

Mediate muscle contraction and electrical signaling in nerve cells.

Question 15

Which of the following best describes the difference between symport and antiport mechanisms?

Accepted Answer

Symport moves two solutes in the same direction; antiport moves them in opposite directions.

Question 16

Which of the following is TRUE about ABC-type ATPases?

Accepted Answer

They are involved in multidrug resistance by exporting drugs from cells.

Question 17

Which of the following is a direct consequence of the Na+/K+ ATPase pump activity in animal cells?

Accepted Answer

High extracellular sodium concentration and high intracellular potassium concentration.

Question 18

Which of the following is a property of porins found in bacterial outer membranes?

Accepted Answer

They allow passage of solutes up to 600 Daltons and are less specific than ion channels.

Question 19

Which of the following best describes the role of the bacteriorhodopsin proton pump in Halobacterium?

Accepted Answer

It uses light energy to pump protons out of the cell, creating a gradient for ATP synthesis.

CH 8 - Transport Across Membranes: Overcoming the Permeability Barrier

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