Q: Which of the following transport processes requires energy input from ATP?

Active transport of sodium ions by the Na\textsuperscript{+}/K\textsuperscript{+} pump.

Q: A cell uses the Na\textsuperscript{+}/K\textsuperscript{+} pump to maintain its membrane potential. For each cycle, how many sodium and potassium ions are transported, and in which directions?

$$3 Na$$\textsuperscript{+}$$ out, 2$ K\textsuperscript{+} in$$

Question 1

Which of the following best explains why phospholipids spontaneously form bilayers in water?

Accepted Answer

Because the hydrophilic heads interact with water while the hydrophobic tails avoid water, minimizing free energy.

Question 2

A red blood cell is placed in a solution and swells until it bursts. Which of the following best describes the tonicity of the solution relative to the cell?

Accepted Answer

The solution is hypotonic to the cell.

Question 3

Which of the following statements about membrane carbohydrates is correct?

Accepted Answer

They are always attached to proteins or lipids on the extracellular side.

Question 4

Which of the following best describes the role of cholesterol in animal cell membranes?

Accepted Answer

It prevents solidification at low temperatures and excessive fluidity at high temperatures.

Question 5

A plant cell is placed in a solution with a lower water potential than its cytoplasm. What will happen to the cell?

Accepted Answer

It will become plasmolyzed as water leaves the cell.

Question 6

Which of the following transport processes requires energy input from ATP?

Accepted Answer

Active transport of sodium ions by the Na	extsuperscript{+}/K	extsuperscript{+} pump.

Question 7

Which of the following is a function of membrane proteins?

Accepted Answer

Cell–cell recognition and signal transduction.

Question 8

A mutation causes LDL receptors to be nonfunctional in a human cell. Which process is directly affected?

Accepted Answer

Receptor-mediated endocytosis of LDL particles.

Question 9

Which of the following best describes the movement of water during osmosis?

Accepted Answer

Water moves from areas of low solute concentration to high solute concentration.

Question 10

A cell uses the Na	extsuperscript{+}/K	extsuperscript{+} pump to maintain its membrane potential. For each cycle, how many sodium and potassium ions are transported, and in which directions?

Accepted Answer

$$3 Na$$	extsuperscript{+}$$ out, 2$ K	extsuperscript{+} in$$

Question 11

Which of the following molecules would most easily cross a pure phospholipid bilayer without the help of a protein?

Accepted Answer

O$$_2$$

Question 12

A patient is given an intravenous solution that is hypertonic relative to their red blood cells. What is the most likely outcome for the cells?

Accepted Answer

The cells will shrink as water leaves them.

Question 13

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It uses membrane proteins to move substances down their concentration gradient.

Question 14

A plant cell with a solute potential ($$\Psi_s) of$$ $$-0.7$$ MPa and a pressure potential ($$\Psi_p) of$$ $$0.5$$ MPa is placed in pure water ($$\Psi = 0). In $$which direction will water move?

Accepted Answer

Water will move into the cell.

Question 15

Which of the following best explains why carbohydrates are always found on the extracellular side of the plasma membrane?

Accepted Answer

They are added in the ER and Golgi and remain on the same side during vesicle fusion.

Question 16

Which of the following is an example of cotransport in human physiology?

Accepted Answer

Na	extsuperscript{+}/glucose transport in the intestines

Question 17

Which of the following scenarios illustrates the importance of membrane fluidity?

Accepted Answer

A nerve cell rapidly fuses vesicles with its plasma membrane to release neurotransmitters.

Question 18

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Synthesis of DNA

Question 19

A cell is placed in a solution and water moves into the cell until it becomes turgid. What can you conclude about the solution and the cell?

Accepted Answer

The solution is hypotonic to the cell.

Question 20

Which of the following best describes the difference between channel proteins and carrier proteins in facilitated diffusion?

Accepted Answer

Channel proteins provide a passageway for specific molecules, while carrier proteins change shape to move molecules across the membrane.

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