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

$$6 \mathrm{CO}_2 + 6 \mathrm{H}_2\mathrm{O} + \text{Energy} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6 \mathrm{O}_2$$

Question 1

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

Accepted Answer

$$6 \mathrm{CO}_2 + 6 \mathrm{H}_2\mathrm{O} + 	ext{Energy} ightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6 \mathrm{O}_2$$

Question 2

Which molecule is reduced during the process of photosynthesis?

Accepted Answer

$$\mathrm{CO}_2$$

Question 3

What is the main function of the light reactions in photosynthesis?

Accepted Answer

To convert light energy into chemical energy in the form of ATP and NADPH

Question 4

Which structure within the chloroplast contains the components necessary for the light reactions?

Accepted Answer

Thylakoid membrane

Question 5

Why do leaves appear green to our eyes?

Accepted Answer

Chlorophyll absorbs red and blue light but reflects green light

Question 6

Which of the following statements about the absorption spectrum of chlorophyll is correct?

Accepted Answer

Chlorophyll a and b absorb light most efficiently in the blue and red regions of the spectrum

Question 7

What is the primary role of the photosystem II (PSII) in the linear electron flow of photosynthesis?

Accepted Answer

To capture light energy and use it to extract electrons from water, producing $$\mathrm{O}_2$$

Question 8

During the light reactions, what is the immediate fate of the electrons that are excited in photosystem II?

Accepted Answer

They are transferred to the primary electron acceptor and then to the electron transport chain

Question 9

How is ATP produced during the light reactions of photosynthesis?

Accepted Answer

By chemiosmosis, as protons flow through ATP synthase in the thylakoid membrane

Question 10

Which of the following best explains why both photosystem II and photosystem I are required for the production of NADPH?

Accepted Answer

The energy from both photosystems is needed to fully energize an electron so it can reduce NADP$$^+$$

Question 11

A plant is exposed to only green light. What would you expect to happen to its rate of photosynthesis and why?

Accepted Answer

The rate of photosynthesis would decrease because chlorophyll reflects green light and does not absorb it efficiently

Question 12

Which of the following is NOT a possible fate of the energy absorbed by a pigment molecule in a plant?

Accepted Answer

The energy is used to synthesize glucose directly

Question 13

What is the main function of carotenoids in the photosynthetic apparatus?

Accepted Answer

They act as accessory pigments, broadening the spectrum of light that can be used for photosynthesis

Question 14

Which of the following best describes the role of the cytochrome complex in the light reactions?

Accepted Answer

It helps pump protons into the thylakoid lumen, contributing to the proton gradient used for ATP synthesis

Question 15

A mutation prevents the formation of the thylakoid membrane in a plant cell. Which process would be directly affected?

Accepted Answer

The light reactions, because the electron transport chain and ATP synthase are located in the thylakoid membrane

Question 16

Which of the following statements about the Calvin cycle is correct?

Accepted Answer

It uses ATP and NADPH produced in the light reactions to reduce $$\mathrm{CO}_2 to $$sugar

Question 17

Why is the splitting of water important in the light reactions of photosynthesis?

Accepted Answer

It provides electrons to replace those lost by P680 in photosystem II and releases $$\mathrm{O}_2 as a $$byproduct

Question 18

Which of the following best explains why having both chlorophyll a and chlorophyll b is advantageous for plants?

Accepted Answer

They absorb slightly different wavelengths, maximizing the amount of light energy captured

Question 19

A scientist isolates chlorophyll from a plant and exposes it to light in a test tube. The chlorophyll fluoresces. What is the best explanation for this observation?

Accepted Answer

The chlorophyll is not properly organized within a photosystem, so the energy is released as fluorescence

Photosynthesis: Metabolic Pathways and Light Reactions (Chapter 10.1–10.5)

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