AP Biology Practice Quiz: Cellular Respiration

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

Test your understanding with short quizzes. This quiz has 16 questions to check your progress.

Question 1 of 16

What are the key products generated from one molecule of glucose during the process of glycolysis?

A)CO2, ATP, and FADH2B)Pyruvate, ATP, and NADHC)Lactic acid, NAD+, and ATPD)Acetyl-CoA, CO2, and NADH

All Questions (16)

What are the key products generated from one molecule of glucose during the process of glycolysis?

A) CO2, ATP, and FADH2

B) Pyruvate, ATP, and NADH

C) Lactic acid, NAD+, and ATP

D) Acetyl-CoA, CO2, and NADH

Correct Answer: B

According to the provided content, 'Glycolysis is a biochemical pathway that releases energy from glucose to form ATP, NADH, and pyruvate.' The other options list products from different stages of respiration or fermentation.

In eukaryotic cells, where do the enzyme-catalyzed reactions of the Krebs cycle occur?

A) Outer mitochondrial membrane

B) Intermembrane space

C) Inner mitochondrial membrane

D) Mitochondrial matrix

Correct Answer: D

The provided content explicitly states, 'The Krebs cycle in the mitochondrial matrix releases CO2, synthesizes ATP, and transfers electrons to NAD+ and FAD.'

What is the primary function of the electron transport chain (ETC) in aerobic respiration?

A) To directly synthesize ATP from ADP and phosphate.

B) To break down pyruvate into CO2.

C) To establish a proton gradient across the inner mitochondrial membrane.

D) To produce alcohol or lactic acid in the absence of oxygen.

Correct Answer: C

The content specifies that the ETC 'transfers electrons... establishing a proton gradient across the inner mitochondrial membrane.' This gradient, in turn, 'drives ATP synthesis.' The ETC itself does not directly synthesize ATP.

Under anaerobic conditions, what is the main purpose of fermentation?

A) To produce a large amount of ATP.

B) To consume excess oxygen.

C) To allow glycolysis to continue.

D) To transport pyruvate into the mitochondrion.

Correct Answer: C

As stated in the provided text, 'Fermentation allows glycolysis to continue in the absence of oxygen.' It achieves this by regenerating the NAD+ needed for glycolysis to proceed, thus allowing for a small but continuous production of ATP.

Which molecules are responsible for transferring electrons from glycolysis and the Krebs cycle to the electron transport chain?

A) ATP and ADP

B) Pyruvate and CO2

C) NADH and FADH2

D) Oxygen and water

Correct Answer: C

The content clearly states, 'Electrons from glycolysis and the Krebs cycle are transferred by NADH and FADH2 to the ETC in the inner mitochondrial membrane.'

Following its formation during glycolysis in an aerobic eukaryotic cell, what is the next step for pyruvate?

A) It is converted to lactic acid in the cytoplasm.

B) It is immediately used by the electron transport chain.

C) It is transported to the mitochondrion for further oxidation.

D) It is broken back down into a 6-carbon sugar.

Correct Answer: C

According to the provided information, 'Pyruvate is transported to the mitochondrion, where its oxidation in the Krebs cycle releases electrons...'

The synthesis of ATP that is driven by the flow of protons through ATP synthase down a concentration gradient is known as:

A) Glycolysis

B) Substrate-level phosphorylation

C) Fermentation

D) Oxidative phosphorylation

Correct Answer: D

The content describes how a proton gradient across the inner mitochondrial membrane 'drives ATP synthesis (oxidative phosphorylation).'

In aerobic respiration, what is the terminal electron acceptor in the electron transport chain?

A) NAD+

B) Oxygen

C) Pyruvate

D) ATP synthase

Correct Answer: B

The provided text specifies that the ETC transfers electrons 'to a terminal electron acceptor (oxygen in aerobic respiration).'

How does the Krebs cycle contribute to the process of oxidative phosphorylation?

A) By directly pumping protons across the inner mitochondrial membrane.

B) By producing the pyruvate that enters the electron transport chain.

C) By generating the electron carriers NADH and FADH2.

D) By consuming CO2 to create a concentration gradient.

Correct Answer: C

The Krebs cycle's primary contribution to oxidative phosphorylation is indirect. It 'releases electrons to form NADH and FADH2,' which then 'are transferred by NADH and FADH2 to the ETC' to power the creation of the proton gradient.

Which statement best summarizes how eukaryotes capture energy from biological macromolecules?

A) Through a single-step reaction that converts glucose and oxygen directly into ATP.

B) Through a process that uses light energy to synthesize ATP.

C) Through a series of enzyme-catalyzed reactions that release energy to synthesize ATP.

D) Through an anaerobic pathway that primarily produces lactic acid.

Correct Answer: C

The content states, 'Aerobic respiration in eukaryotes involves a series of enzyme-catalyzed reactions that capture energy from macromolecules.' This is the most accurate and comprehensive description among the choices.

The proton gradient that drives ATP synthesis during oxidative phosphorylation is established across which specific mitochondrial structure?

A) The mitochondrial matrix

B) The outer mitochondrial membrane

C) The cytoplasm

D) The inner mitochondrial membrane

Correct Answer: D

The provided text repeatedly states that the electron transport chain establishes a proton gradient 'across the inner mitochondrial membrane.'

Which of the following sets of molecules are all released or synthesized during the Krebs cycle?

A) Glucose, O2, and ATP

B) Pyruvate, NADH, and FADH2

C) CO2, ATP, and NADH

D) Lactic acid, CO2, and ATP

Correct Answer: C

The content specifies that the Krebs cycle 'releases CO2, synthesizes ATP, and transfers electrons to NAD+ and FAD' (forming NADH and FADH2). Option C correctly lists CO2, ATP, and NADH as direct outputs.

The fact that cellular respiration and fermentation are characteristic of all known life forms is evidence that these processes...

A) evolved very recently in the history of life on Earth.

B) are the only ways organisms can obtain energy.

C) were present in an early common ancestor of all life.

D) require complex, multicellular organization to function.

Correct Answer: C

The provided text states that these processes 'are characteristic of all life forms.' Such a universally conserved core metabolic process strongly suggests it is ancient and was present in a last universal common ancestor before the major domains of life diverged.

A toxin creates pores in the inner mitochondrial membrane, allowing protons to pass through freely. Which of the following would be the most direct consequence?

A) The rate of glycolysis would immediately stop.

B) The proton gradient would be dissipated, halting ATP synthesis via oxidative phosphorylation.

C) The Krebs cycle would accelerate to produce more NADH and FADH2.

D) The cell would switch to fermentation, even in the presence of oxygen.

Correct Answer: B

The synthesis of ATP via oxidative phosphorylation is driven by the proton gradient. If protons can freely pass through the membrane, the gradient cannot be established or maintained. This would uncouple the electron transport chain from ATP synthesis, causing it to stop.

The transfer of electrons by NADH and FADH2 to the electron transport chain is a critical step that directly links which two major parts of cellular respiration?

A) Fermentation and the Krebs cycle

B) Glycolysis and Fermentation

C) Glycolysis/Krebs cycle and Oxidative Phosphorylation

D) Pyruvate oxidation and Glycolysis

Correct Answer: C

The content states that electrons from glycolysis and the Krebs cycle are transferred via NADH and FADH2 to the ETC. The ETC's function is to power oxidative phosphorylation. Therefore, these electron carriers link the initial energy-releasing pathways with the final ATP-synthesis pathway.

Which process is common to both aerobic cellular respiration and fermentation?

A) The Krebs Cycle

B) Glycolysis

C) Oxidative Phosphorylation

D) The Electron Transport Chain

Correct Answer: B

The content states that 'Fermentation allows glycolysis to continue in the absence of oxygen,' implying that glycolysis is the foundational pathway that occurs before fermentation. Glycolysis is also the first step in aerobic respiration. Therefore, it is common to both processes.