AP Biology Practice Quiz: Photosynthesis

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

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

Question 1 of 16

According to the provided text, where within the chloroplast does the Calvin cycle take place?

A)In the thylakoid membranesB)Within the granaC)In the stromaD)Across the outer chloroplast membrane

All Questions (16)

According to the provided text, where within the chloroplast does the Calvin cycle take place?

A) In the thylakoid membranes

B) Within the grana

C) In the stroma

D) Across the outer chloroplast membrane

Correct Answer: C

The provided content explicitly states in point 4 that 'the Calvin cycle occurs in the stroma.'

What is the source of the electrons that replace those lost from photosystem II after they are excited by light energy?

A) The splitting of carbon dioxide

B) The splitting of water

C) Electrons recycled from photosystem I

D) NADPH from the Calvin cycle

Correct Answer: B

Point 7 of the content states, 'Water is split to replace electrons lost from photosystem II.'

What is the primary purpose of the ATP and NADPH produced during the light-dependent reactions?

A) To directly synthesize oxygen

B) To power the production of carbohydrates in the Calvin cycle

C) To establish a proton gradient across the thylakoid membrane

D) To absorb light energy in the chlorophyll molecules

Correct Answer: B

Point 5 states that ATP and NADPH 'power the production of organic molecules in the Calvin cycle,' and point 11 reiterates that this energy 'powers the production of carbohydrates from CO2 in the Calvin cycle.'

The synthesis of ATP via ATP synthase in the chloroplast is directly driven by which of the following?

A) The absorption of light by chlorophyll

B) The transfer of electrons to NADP+

C) The flow of protons down their electrochemical gradient

D) The splitting of water molecules

Correct Answer: C

Point 10 explains that 'The proton gradient drives the synthesis of ATP from ADP and inorganic phosphate via ATP synthase.'

In the electron transport chain associated with photosystem I, what is the final molecule to which electrons are transferred?

A) Water (H2O)

B) ATP synthase

C) Photosystem II

D) NADP+

Correct Answer: D

Point 6 specifies that 'In photosynthesis, electrons are transferred to NADP+ to form NADPH in photosystem I.'

Which of the following lists the necessary inputs for the overall process of photosynthesis as described in the text?

A) Carbohydrates and oxygen

B) Light energy, carbon dioxide, and water

C) ATP, NADPH, and oxygen

D) Chlorophyll, protons, and electrons

Correct Answer: B

Point 3 states, 'Photosynthesis uses light energy, carbon dioxide, and water to produce carbohydrates and oxygen...'

How are photosystems I and II functionally connected within the thylakoid membrane?

A) By the movement of ATP through ATP synthase

B) By the splitting of water molecules

C) By the transfer of electrons through an ETC

D) By the diffusion of CO2 into the stroma

Correct Answer: C

Point 8 clearly states that 'Photosystems I and II, embedded in the thylakoid membranes, are connected by the transfer of electrons through an ETC.'

The process by which a proton gradient is used to generate ATP during the light-dependent reactions is called:

A) The Calvin cycle

B) Electron excitation

C) Photophosphorylation

D) Carbon fixation

Correct Answer: C

Point 10 describes the synthesis of ATP using the proton gradient and explicitly names the process 'photophosphorylation.'

The light-dependent reactions of photosynthesis, including the actions of the photosystems and electron transport chains, occur specifically in which location?

A) The stroma

B) The cytoplasm of the cell

C) The thylakoid membranes

D) The mitochondrial matrix

Correct Answer: C

Point 4 states that 'the light-dependent reactions occur in the thylakoid membranes.' Points 8 and 9 further confirm that the photosystems and ETC are embedded in these membranes.

What is the immediate consequence of chlorophylls absorbing light energy?

A) ATP is synthesized from ADP

B) Water molecules are split

C) Electrons in the photosystems are excited

D) Carbon dioxide is converted to carbohydrates

Correct Answer: C

Point 7 describes the initial step: 'During photosynthesis, chlorophylls absorb light energy, exciting electrons in photosystems I and II.'

Which of the following best describes the primary function of the Calvin cycle?

A) To capture light energy and produce ATP and NADPH

B) To use ATP and NADPH to produce carbohydrates from CO2

C) To split water and release oxygen

D) To establish a proton gradient across the thylakoid membrane

Correct Answer: B

Point 11 summarizes the role of the Calvin cycle: 'The energy captured in ATP and NADPH from the light reactions powers the production of carbohydrates from CO2 in the Calvin cycle.'

The passage of electrons through the electron transport chain (ETC) between photosystem II and photosystem I leads directly to which of the following events?

A) The reduction of NADP+ to NADPH

B) The absorption of light by chlorophyll

C) The establishment of an electrochemical proton gradient

D) The fixation of carbon dioxide into organic molecules

Correct Answer: C

Point 9 states, 'As electrons pass through the ETC, an electrochemical proton gradient is established across the thylakoid membrane.' The reduction of NADP+ occurs after photosystem I.

Based on the provided information, in which type of organism did photosynthesis first evolve?

A) Eukaryotic algae

B) Land plants

C) Prokaryotic organisms

D) Mitochondrial ancestors

Correct Answer: C

Point 3 explicitly mentions that photosynthesis 'first evolved in prokaryotic organisms.'

A toxin is introduced that blocks the function of ATP synthase in the chloroplast. Which of the following processes would be most immediately and directly inhibited?

A) The absorption of light by photosystem II

B) The transfer of electrons along the electron transport chain

C) The synthesis of ATP from ADP and inorganic phosphate

D) The splitting of water to replace electrons

Correct Answer: C

Point 10 identifies ATP synthase as the enzyme that synthesizes ATP from ADP and inorganic phosphate. Inhibiting this enzyme would directly stop this specific process.

The structural organization of thylakoids into stacks (grana) within the chloroplast primarily serves to increase the efficiency of which process?

A) The synthesis of carbohydrates from CO2 in the stroma

B) The capture of light energy by the light-dependent reactions

C) The diffusion of water and carbon dioxide into the chloroplast

D) The evolution of photosynthesis in prokaryotic cells

Correct Answer: B

The text states that the light-dependent reactions occur in the thylakoid membranes (point 4), which contain the photosystems (point 8). The organization of these membranes into grana is a structural feature (point 1) that allows for more surface area to capture light and carry out these reactions efficiently.

Which statement best describes the relationship between the two main stages of photosynthesis?

A) The Calvin cycle produces water and light energy, which are used by the light-dependent reactions.

B) The light-dependent reactions and the Calvin cycle occur independently of each other.

C) The light-dependent reactions produce energy-carrying molecules that are used to power the Calvin cycle.

D) The Calvin cycle captures light energy, which is then converted to ATP and NADPH in the light-dependent reactions.

Correct Answer: C

Point 5 states that the light-dependent reactions produce ATP and NADPH, which 'power the production of organic molecules in the Calvin cycle.' Point 11 reinforces this by stating the energy from these molecules 'powers the production of carbohydrates from CO2 in the Calvin cycle.' This shows a direct dependency of the Calvin cycle on the products of the light reactions.