Q: Which equation correctly represents the movement of sodium ions ($$\mathrm{Na^+}) $$against their concentration gradient via the sodium-potassium pump?

$$3\ \mathrm{Na^+}_{\text{in}} + 2\ \mathrm{K^+}_{\text{out}} + \mathrm{ATP} \rightarrow 3\ \mathrm{Na^+}_{\text{out}} + 2\ \mathrm{K^+}_{\text{in}} + \mathrm{ADP} + \mathrm{P_i}$$

Q: In the context of membrane transport, which equation best represents the movement of water across a semipermeable membrane due to osmosis?

$$\Delta \Psi = \Psi_{\text{inside}} - \Psi_{\text{outside}}$$

Question 1

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

Accepted Answer

They create a selectively permeable bilayer, allowing certain molecules to pass while blocking others.

Question 2

A cell is placed in a solution with a higher concentration of solutes than inside the cell. What process will most likely occur, and what is the expected outcome for the cell?

Accepted Answer

Osmosis will cause water to leave the cell, resulting in cell shrinkage (crenation).

Question 3

Which equation correctly represents the movement of sodium ions ($$\mathrm{Na^+}) $$against their concentration gradient via the sodium-potassium pump?

Accepted Answer

$$3\ \mathrm{Na^+}_{	ext{in}} + 2\ \mathrm{K^+}_{	ext{out}} + \mathrm{ATP} ightarrow 3\ \mathrm{Na^+}_{	ext{out}} + 2\ \mathrm{K^+}_{	ext{in}} + \mathrm{ADP} + \mathrm{P_i}$$

Question 4

Which of the following best explains why steroid hormones can easily cross the plasma membrane?

Accepted Answer

Steroid hormones are nonpolar and lipid-soluble, allowing them to diffuse through the hydrophobic core of the membrane.

Question 5

A neuron releases dopamine into the synaptic cleft. Which type of membrane transport is primarily responsible for clearing excess dopamine from the synapse?

Accepted Answer

Facilitated diffusion through dopamine transporter proteins (DATs)

Question 6

Which of the following scenarios best illustrates passive transport?

Accepted Answer

Glucose moving into a cell via a channel protein down its concentration gradient

Question 7

A patient is given a drug that blocks dopamine transporter proteins (DATs). What is the most likely effect on dopamine signaling in the brain?

Accepted Answer

Dopamine will accumulate in the synaptic cleft, leading to prolonged and amplified neuronal signaling.

Question 8

Which of the following best describes the difference between facilitated diffusion and active transport?

Accepted Answer

Facilitated diffusion moves molecules down their concentration gradient without energy, while active transport moves molecules against their gradient using ATP.

Question 9

In the context of membrane transport, which equation best represents the movement of water across a semipermeable membrane due to osmosis?

Accepted Answer

$$\Delta \Psi = \Psi_{	ext{inside}} - \Psi_{	ext{outside}}$$

Question 10

A cancer cell is able to pump out chemotherapy drugs, making it resistant to treatment. Which type of membrane transport is most likely responsible for this resistance?

Accepted Answer

Active transport using ATP-powered efflux pumps

Question 11

Which of the following statements about cholesterol in the plasma membrane is correct?

Accepted Answer

Cholesterol stabilizes membrane fluidity by preventing extremes of rigidity and fluidity.

Question 12

A red blood cell is placed in pure water. What will happen to the cell, and which transport process is responsible?

Accepted Answer

The cell will swell and may burst due to osmosis of water into the cell.

Question 13

Which of the following best explains why glucose requires a transporter protein to enter most cells?

Accepted Answer

Glucose is a large, polar molecule that cannot cross the hydrophobic core of the membrane without assistance.

Question 14

Which of the following is a real-world example of bulk transport across the plasma membrane?

Accepted Answer

White blood cells engulfing bacteria via endocytosis

Question 15

A cell uses ATP to move potassium ions ($$\mathrm{K^+}) $$into the cell against their concentration gradient. Which type of transport is this?

Accepted Answer

Active transport

Question 16

Which of the following best describes the effect of chronic cocaine use on dopamine signaling in the brain?

Accepted Answer

It downregulates dopamine receptors, making natural rewards less satisfying.

Question 17

Which of the following is a consequence of dopamine transporter (DAT) inhibition in the synaptic cleft?

Accepted Answer

Increased dopamine concentration and prolonged neuronal signaling

Question 18

Which of the following best explains why polar, charged molecules cannot easily cross the plasma membrane?

Accepted Answer

The hydrophobic core of the lipid bilayer repels polar and charged molecules.

Question 19

Which of the following is the correct sequence for normal dopamine transmission in the synaptic cleft?

Accepted Answer

Release, binding to postsynaptic receptors, reuptake by DATs, termination

Membrane Transport, Lipids, and Drug Addiction: Study Notes for General Biology

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