Question 1

In the light reactions of photosynthesis, what is the primary function of the molecule circled in blue in the first image?

Accepted Answer

To split water and release oxygen

Question 2

The orange line in the first image represents the movement of electrons. Which of the following best describes the fate of these electrons during the light reactions?

Accepted Answer

They are transferred from water to NADP$$^+$$, forming NADPH

Question 3

In the second image, which process is directly responsible for the generation of the proton gradient across the thylakoid membrane?

Accepted Answer

The flow of electrons through the cytochrome complex

Question 4

What is the main role of ATP synthase, as depicted in the second image?

Accepted Answer

To use the proton gradient to synthesize ATP from ADP and $$P_i$$

Question 5

In the Calvin cycle (third image), which enzyme catalyzes the fixation of CO$$_2 to $$ribulose bisphosphate (RuBP)?

Accepted Answer

Rubisco

Question 6

During the reduction phase of the Calvin cycle, which molecules are consumed to convert 3-phosphoglycerate into glyceraldehyde 3-phosphate (G3P)?

Accepted Answer

ATP and NADPH

Question 7

Which of the following best explains why the light reactions must occur before the Calvin cycle?

Accepted Answer

The light reactions produce ATP and NADPH, which are required for the Calvin cycle

Question 8

If a plant is exposed to a chemical that inhibits the cytochrome complex, what would be the most immediate effect on photosynthesis?

Accepted Answer

A decrease in ATP production due to a reduced proton gradient

Question 9

Which of the following equations correctly represents the overall process of the light reactions of photosynthesis?

Accepted Answer

$$2 H_2O + 2 NADP^+ + 3 ADP + 3 P_i + light \rightarrow O_2$ + 2 NADPH + 3 ATP$$

Question 10

A mutation causes a plant to produce a nonfunctional NADP$$^+$$ reductase. Which of the following would be the most direct consequence?

Accepted Answer

The plant would be unable to produce NADPH, limiting the Calvin cycle

Question 11

Which of the following best describes the relationship between the light reactions and the Calvin cycle?

Accepted Answer

The light reactions provide ATP and NADPH to the Calvin cycle, which uses them to fix carbon

Question 12

If the thylakoid membrane becomes leaky to protons, what would be the most likely effect on ATP synthesis?

Accepted Answer

ATP synthesis would decrease because the proton gradient would dissipate

Question 13

Which of the following is a direct product of the Calvin cycle that can be used to synthesize glucose and other organic compounds?

Accepted Answer

Glyceraldehyde 3-phosphate (G3P)

Question 14

During the Calvin cycle, how many molecules of CO$$_2$$ must enter the cycle to produce one molecule of G3P?

Accepted Answer

$$3$$

Question 15

Which of the following best explains why plants need both mitochondria and chloroplasts?

Accepted Answer

Chloroplasts capture light energy to make sugars, while mitochondria break down sugars to produce ATP for cellular work

Photosynthesis: The Light Reactions and Calvin Cycle

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