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

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

Question 1

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

Accepted Answer

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

Question 2

Where in the chloroplast does the Calvin cycle take place?

Accepted Answer

In the stroma

Question 3

Which molecule acts as the primary electron donor in the light reactions of photosynthesis?

Accepted Answer

Water ($$\mathrm{H}_2\mathrm{O})$$

Question 4

What is the main function of the light-harvesting complex in photosystems?

Accepted Answer

To capture photons and transfer energy to the reaction-center chlorophyll

Question 5

During the light reactions, protons are pumped from the stroma into which compartment, and why is this important?

Accepted Answer

Into the thylakoid lumen; this creates a proton gradient used to drive ATP synthesis via chemiosmosis

Question 6

Which of the following best describes the role of NADPH in photosynthesis?

Accepted Answer

It donates high-energy electrons for the reduction of 3-phosphoglycerate in the Calvin cycle

Question 7

How many molecules of ATP and NADPH are consumed to produce one molecule of glucose during the Calvin cycle?

Accepted Answer

$$18$$ ATP and $$12$$ NADPH

Question 8

Which phase of the Calvin cycle is responsible for incorporating carbon dioxide into an organic molecule?

Accepted Answer

Carbon fixation phase

Question 9

A plant is exposed to a herbicide that blocks the regeneration of ribulose 1,5-bisphosphate (RuBP). What is the most immediate effect on the Calvin cycle?

Accepted Answer

The cycle will halt because CO$$_2$$ cannot be fixed without RuBP

Question 10

Which of the following statements about the movement of electrons during the light reactions is correct?

Accepted Answer

Electrons move from water to NADP$$^+$$ via the 'Z' pathway, passing through Photosystem II, the electron transport chain, and Photosystem I

Question 11

If a plant is placed in an environment with no light, which of the following processes will immediately stop?

Accepted Answer

The production of ATP and NADPH by the light reactions

Question 12

Which pigment is primarily responsible for absorbing light energy in the reaction center of Photosystem II?

Accepted Answer

Chlorophyll a (P680)

Question 13

What is the fate of the oxygen atoms from water molecules split during the light reactions?

Accepted Answer

They are released as molecular oxygen ($$\mathrm{O}_2) $$into the atmosphere

Question 14

Which of the following best explains why the Calvin cycle is sometimes called the 'dark reactions'?

Accepted Answer

It does not directly require light to proceed, but depends on ATP and NADPH from the light reactions

Question 15

A mutation prevents a plant from producing carotenoids. What is the most likely consequence?

Accepted Answer

The plant will be more susceptible to damage from excess light energy

Question 16

How many molecules of CO$$_2$$ must enter the Calvin cycle to produce one molecule of glucose?

Accepted Answer

6

Question 17

Which of the following is a direct product of the Calvin cycle that can be used to synthesize glucose, cellulose, or starch?

Accepted Answer

Glyceraldehyde 3-phosphate (G3P)

Question 18

If the proton gradient across the thylakoid membrane is dissipated (for example, by an uncoupling agent), what is the most immediate effect on photosynthesis?

Accepted Answer

ATP synthesis by ATP synthase will decrease or stop

Question 19

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, which are used by the Calvin cycle to fix carbon dioxide

Question 20

A plant cell is exposed to a toxin that inhibits ATP synthase in the thylakoid membrane. Which process will be directly affected?

Accepted Answer

Photophosphorylation

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