Q: Which of the following equations correctly represents the overall process of photosynthesis?

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

Question 1

Which of the following best describes the role of NADP+ in the light reactions of photosynthesis?

Accepted Answer

It is the final electron acceptor, becoming reduced to NADPH, which then carries high-energy electrons to the Calvin cycle.

Question 2

A plant is exposed to only green light. 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 chlorophyll.

Question 3

Which of the following correctly matches the location and function of the Calvin cycle in the chloroplast?

Accepted Answer

It occurs in the stroma and uses ATP and NADPH to fix carbon dioxide into sugar.

Question 4

During the light reactions, what is the original source of electrons that are eventually transferred to NADP+?

Accepted Answer

Water

Question 5

Which of the following best explains why deforestation can contribute to increased atmospheric CO2 levels?

Accepted Answer

Fewer trees mean less carbon fixation, so less CO2 is removed from the atmosphere.

Question 6

Which of the following is a correct statement about the absorption and action spectra of photosynthetic pigments?

Accepted Answer

The absorption spectrum shows the wavelengths of light absorbed by a pigment, while the action spectrum shows the effectiveness of different wavelengths in driving photosynthesis.

Question 7

A mutation causes a plant to lack Photosystem II but still have functional Photosystem I. Which of the following would most likely occur?

Accepted Answer

The plant could perform cyclic electron flow, producing ATP but not NADPH or O2.

Question 8

Which enzyme catalyzes the first step of the Calvin cycle, and what is its substrate?

Accepted Answer

Rubisco; carbon dioxide and RuBP

Question 9

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

Accepted Answer

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

Question 10

Which of the following best describes photophosphorylation in chloroplasts?

Accepted Answer

The process by which light energy is used to add a phosphate group to ADP, forming ATP.

Question 11

A scientist measures the pH inside the thylakoid space and the stroma of a chloroplast during the light reactions. Which of the following results would she most likely observe, and why?

Accepted Answer

The thylakoid space has a lower pH than the stroma because protons accumulate inside the thylakoid during electron transport.

Question 12

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

Accepted Answer

It uses ATP and NADPH to convert CO2 into G3P.

Question 13

If a plant's stomata are closed during a hot, dry day, which of the following is most likely to occur?

Accepted Answer

CO2 uptake will decrease, reducing the rate of the Calvin cycle.

Question 14

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

Accepted Answer

Chlorophyll reflects and transmits green light while absorbing other wavelengths.

Question 15

Which of the following is a function of carotenoids in plant cells?

Accepted Answer

They provide photoprotection by dissipating excess light energy.

Question 16

How many turns of the Calvin cycle are required for the net production of one molecule of glyceraldehyde 3-phosphate (G3P)?

Accepted Answer

Three

Question 17

Which of the following best describes the difference between linear and cyclic electron flow in the light reactions?

Accepted Answer

Linear flow involves both Photosystem I and II, producing ATP, NADPH, and O2; cyclic flow involves only Photosystem I and produces ATP but not NADPH or O2.

Question 18

Which of the following is a real-world consequence of the Calvin cycle's ability to fix carbon?

Accepted Answer

It helps reduce atmospheric CO2, mitigating climate change.

Question 19

Which of the following best explains the relationship between chemiosmosis in mitochondria and chloroplasts?

Accepted Answer

Both use a proton gradient to drive ATP synthesis, but mitochondria use energy from food molecules while chloroplasts use light energy.

Photosynthesis: Conversion of Light Energy to Chemical Energy

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