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

Question 1

Which of the following best describes the main function of the light reactions in photosynthesis?

Accepted Answer

To split water, generate ATP and NADPH, and release oxygen

Question 2

What is the primary role of the enzyme Rubisco in the Calvin cycle?

Accepted Answer

To catalyze the fixation of CO$$_2 to $$ribulose bisphosphate (RuBP)

Question 3

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

Accepted Answer

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

Question 4

Why is cyclic electron flow important in the light reactions of photosynthesis?

Accepted Answer

It allows for the production of extra ATP without generating NADPH or O$$_2$$

Question 5

Which of the following best explains why C$$_4$$ plants are more efficient than C$$_3$$ plants in hot, dry climates?

Accepted Answer

C$$_4$$ plants concentrate CO$$_2 in $$bundle sheath cells, reducing photorespiration by Rubisco

Question 6

During chemiosmosis in chloroplasts, what is the direct source of energy used by ATP synthase to produce ATP?

Accepted Answer

The flow of H$$^+$$ ions down their concentration gradient from the thylakoid space to the stroma

Question 7

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

Accepted Answer

Glyceraldehyde 3-phosphate (G3P)

Question 8

Photorespiration is considered wasteful because:

Accepted Answer

It consumes O$$_2$$ and releases CO$$_2$$, reducing the efficiency of photosynthesis

Question 9

Which enzyme in C$$_4$$ plants initially fixes CO$$_2$$ before it enters the Calvin cycle?

Accepted Answer

PEP carboxylase

Question 10

CAM plants are adapted to arid environments by:

Accepted Answer

Opening stomata at night to fix CO$$_2$$ and closing them during the day to minimize water loss

Question 11

Which of the following statements about the wave and particle nature of light is correct in the context of photosynthesis?

Accepted Answer

Light behaves as both a wave and a particle, and its photons can excite electrons in pigment molecules

Question 12

If the concentration of O$$_2$$ increases relative to CO$$_2 in a $$plant cell, what is the most likely effect on Rubisco activity?

Accepted Answer

Rubisco will increase the rate of photorespiration, reducing photosynthetic efficiency

Question 13

Which of the following best explains why increasing atmospheric CO$$_2$$ levels may not always lead to higher crop yields in C$$_3$$ plants?

Accepted Answer

Higher temperatures can increase O$$_2$$ binding by Rubisco, offsetting the benefits of increased CO$$_2$$

Question 14

Which of the following is NOT a product of the light reactions of photosynthesis?

Accepted Answer

Glucose

Question 15

In the Calvin cycle, how many molecules of CO$$_2$$ must enter the cycle to produce one molecule of glyceraldehyde 3-phosphate (G3P)?

Accepted Answer

Three

Question 16

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

Accepted Answer

It acts as an electron donor in the Calvin cycle, reducing 3-phosphoglycerate to G3P

Question 17

Which of the following is a key difference between C$$_4$$ and CAM plants?

Accepted Answer

C$$_4$$ plants separate carbon fixation and the Calvin cycle by cell type, while CAM plants separate them by time of day

Question 18

A mutation in a plant prevents the regeneration of RuBP in the Calvin cycle. What would be the immediate consequence?

Accepted Answer

The plant would be unable to fix additional CO$$_2$$, halting the Calvin cycle

Question 19

Which of the following statements about chemiosmosis in mitochondria and chloroplasts is correct?

Accepted Answer

Both use a proton gradient to drive ATP synthesis via ATP synthase

Photosynthesis: Metabolic Pathways and Adaptations (Chapter 10.1–10.5)

Study Guide - Practice Questions