$$6CO_2 + 6H_2O + \text{light energy} \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 1

Which molecule acts as a high-energy electron shuttle during the light reactions of photosynthesis?

Accepted Answer

NADPH

Question 2

During the light reactions of photosynthesis, what is the primary role of water?

Accepted Answer

To provide electrons for the electron transport chain

Question 3

Which of the following best describes the Calvin cycle?

Accepted Answer

A series of reactions that use ATP and NADPH to convert carbon dioxide into sugar

Question 4

What is the main product of the Calvin cycle that plants use to make glucose?

Accepted Answer

Glyceraldehyde-3-phosphate (G3P)

Question 5

Which equation correctly represents the overall process of photosynthesis?

Accepted Answer

$$6CO_2 + 6H_2O + 	ext{light energy} ightarrow C_6H_{12}O_6$ + 6O_2$$

Question 6

In the electron transport chain of photosynthesis, what happens when an electron reaches the center of a photosystem?

Accepted Answer

It is elevated to a high-energy state

Question 7

Which of the following is a direct output of the light reactions in photosynthesis?

Accepted Answer

ATP and NADPH

Question 8

Why are the products of the Calvin cycle essential for life on Earth?

Accepted Answer

They provide sugars that serve as energy sources for all plants and animals

Question 9

Which statement best explains the role of chlorophyll in photosynthesis?

Accepted Answer

It absorbs light energy, which excites electrons to a higher energy state

Question 10

During photosynthesis, which process is responsible for the release of oxygen?

Accepted Answer

Splitting of water molecules during the light reactions

Question 11

If a plant is exposed to light but deprived of carbon dioxide, which stage of photosynthesis will be directly affected?

Accepted Answer

The Calvin cycle

Question 12

Which of the following best describes the flow of electrons during the light reactions?

Accepted Answer

From water to NADP+ via photosystems and electron transport chain

Question 13

A scientist measures the rate of photosynthesis in a leaf and finds it decreases when NADPH levels are low. What is the most likely explanation?

Accepted Answer

NADPH is required to provide high-energy electrons for the Calvin cycle

Question 14

Which of the following is the correct sequence of events in the light reactions?

Accepted Answer

Absorption of light by chlorophyll, excitation of electrons, electron transport chain, production of ATP and NADPH

Question 15

Which formula represents the production of ATP during the light reactions?

Accepted Answer

$$ADP + P_i + 	ext{energy} ightarrow ATP$$

Question 16

Which structure in the chloroplast is the site of the Calvin cycle?

Accepted Answer

Stroma

Question 17

A mutation prevents a plant from producing ATP during the light reactions. Which process will be most directly affected?

Accepted Answer

Synthesis of sugar in the Calvin cycle

Question 18

Which of the following is NOT a direct input required for the Calvin cycle?

Accepted Answer

Oxygen

Question 19

If the electron transport chain in photosynthesis is inhibited, which of the following will most likely occur?

Accepted Answer

Production of ATP and NADPH will decrease

Question 20

Which of the following best explains why photosynthesis is essential for heterotrophic organisms?

Accepted Answer

It produces organic molecules and oxygen that heterotrophs depend on for energy and respiration

Photosynthesis: Light Reactions and the Calvin Cycle

Study Guide - Practice Questions