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AP Biology Practice Quiz: Mechanisms of Transport

Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026

Test your understanding with short quizzes. This quiz has 7 questions to check your progress.

Question 1 of 7

Which of the following processes is explicitly described as requiring metabolic energy to move ions and molecules across a cell membrane?

All Questions (7)

Which of the following processes is explicitly described as requiring metabolic energy to move ions and molecules across a cell membrane?

A) Passive Diffusion

B) Osmosis

C) Active Transport

D) Facilitated Diffusion

Correct Answer: C

The provided text directly states that 'Metabolic energy (e.g., from ATP) is required for the active transport of molecules and ions across the membrane.' The other options are forms of passive transport that do not require metabolic energy.

According to the text, what is the direct energy source that powers membrane proteins like the Na+/K+ pump?

A) The electrochemical gradient

B) Sunlight

C) Kinetic energy of molecules

D) Metabolic energy from ATP

Correct Answer: D

The content specifies that 'Metabolic energy (e.g., from ATP) is required for the active transport...via membrane proteins like the Na+/K+ pump.' This identifies ATP as the direct energy source.

What is a primary function of active transport, as described in the provided information?

A) To allow molecules to move randomly across the membrane

B) To establish and maintain electrochemical gradients

C) To achieve equilibrium of ions on both sides of the membrane

D) To facilitate the movement of water into the cell

Correct Answer: B

The text states that active transport 'establishes and maintains electrochemical gradients.' This process moves substances against their natural flow, creating a potential energy difference across the membrane.

A cell is observed to have a high concentration of potassium ions inside and a high concentration of sodium ions outside. Based on the text, which specific mechanism is responsible for maintaining this state?

A) Simple diffusion through the lipid bilayer

B) The action of the Na+/K+ pump

C) The process of osmosis

D) Passive ion channels

Correct Answer: B

The text provides the Na+/K+ pump as a specific example of a membrane protein that uses active transport to establish and maintain electrochemical gradients, which includes the differential concentrations of sodium and potassium ions across the membrane.

The movement of ions and molecules across a membrane via active transport is directly carried out by which of the following cellular components?

A) The phospholipid bilayer itself

B) Free-floating ribosomes in the cytoplasm

C) Membrane proteins

D) Cholesterol molecules

Correct Answer: C

The content explicitly mentions that active transport functions 'via membrane proteins like the Na+/K+ pump,' indicating that these proteins are the direct facilitators of this process.

If a metabolic poison that specifically inhibits the production of ATP were introduced to a cell, which of the following transport processes would be most immediately and directly affected?

A) The movement of oxygen across the membrane

B) The movement of water through aquaporins

C) The maintenance of an electrochemical gradient by the Na+/K+ pump

D) The diffusion of small, nonpolar molecules through the lipid bilayer

Correct Answer: C

The text links ATP directly to active transport and the function of the Na+/K+ pump. Without ATP, the pump cannot function, and the cell would be unable to maintain its electrochemical gradient. The other options describe forms of passive transport which do not require ATP.

Active transport is fundamentally different from passive transport because it moves molecules...

A) only into the cell, never out of it.

B) with the help of proteins, whereas passive transport does not.

C) against an electrochemical gradient.

D) at a much faster rate than passive transport.

Correct Answer: C

The text explains that active transport uses energy to 'establish and maintain electrochemical gradients.' This implies moving substances from a lower concentration to a higher concentration, or against their electrochemical gradient, which is the key distinction from passive transport.