Question 1

Which of the following best describes the overall chemical equation for photosynthesis in plants?

Accepted Answer

$CO_2 + 2H_2O + light\ energy \rightarrow CH_2O + O_2 + H_2O$

Question 2

Which structure within the chloroplast is the primary site for the light-dependent reactions of photosynthesis?

Accepted Answer

Thylakoid membrane

Question 3

What is the main function of chlorophyll a in photosynthesis?

Accepted Answer

To capture photons and transfer energy to the reaction center

Question 4

Which of the following statements about the energy of photons is correct?

Accepted Answer

Photons with shorter wavelengths have higher energy

Question 5

During the light reactions, what is the immediate fate of the electrons released from water splitting in Photosystem II?

Accepted Answer

They replenish the special pair of chlorophyll a molecules (P680)

Question 6

Which of the following best explains why leaves appear green to our eyes?

Accepted Answer

Chlorophyll reflects and transmits green light while absorbing other wavelengths

Question 7

What is the primary role of the proton gradient established across the thylakoid membrane during the light reactions?

Accepted Answer

To power ATP synthase for ATP production

Question 8

Which of the following is a correct comparison between chemiosmosis in mitochondria and chloroplasts?

Accepted Answer

Chloroplasts pump protons from the stroma into the thylakoid lumen, while mitochondria pump protons from the matrix into the intermembrane space

Question 9

Which pigment is primarily responsible for photoprotection in plants, and what wavelengths does it absorb?

Accepted Answer

Carotenoids; absorb 450-500 nm

Question 10

A plant is exposed to only green light (around 550 nm). What is the most likely effect on the rate of photosynthesis, and why?

Accepted Answer

The rate will decrease because green light is mostly reflected, not absorbed, by photosynthetic pigments

Question 11

Which of the following correctly matches the photosystem with its primary function in the light reactions?

Accepted Answer

Photosystem II: Splits water and releases O$_2$

Question 12

What is the correct sequence of events during the light-dependent reactions of photosynthesis?

Accepted Answer

Photon absorption by PSII, water splitting, electron transport chain, photon absorption by PSI, NADPH formation

Question 13

Which of the following best describes the redox changes that occur during photosynthesis?

Accepted Answer

H$_2$O is oxidized and CO$_2$ is reduced

Question 14

If a mutation prevented the formation of the proton gradient across the thylakoid membrane, which process would be directly affected?

Accepted Answer

Synthesis of ATP via ATP synthase

Question 15

Which of the following is a direct product of the light reactions that is used in the Calvin cycle?

Accepted Answer

NADPH

Question 16

What is the role of the primary electron acceptor in the reaction center of a photosystem?

Accepted Answer

It captures the excited electron from chlorophyll a, initiating electron flow

Question 17

Which of the following best explains why the light reactions are considered endergonic?

Accepted Answer

They require an input of light energy to drive the transfer of electrons from water to NADP$^+$

Question 18

A scientist isolates a mutant plant that cannot produce functional P680 chlorophyll. Which process would be directly impaired?

Accepted Answer

Splitting of water and initial electron flow in Photosystem II

Question 19

Which of the following statements about autotrophs and heterotrophs is correct?

Accepted Answer

Autotrophs synthesize organic molecules using light or chemical energy

Photosynthesis: Structure, Function, and Mechanisms

Study Guide - Practice Questions