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

Question 1

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

Accepted Answer

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

Question 2

What is the primary function of the light reactions in photosynthesis?

Accepted Answer

To convert solar energy into chemical energy in the form of ATP and NADPH

Question 3

Which pigment is directly involved in the light reactions of photosynthesis?

Accepted Answer

Chlorophyll a

Question 4

Why do most leaves appear green to the human eye?

Accepted Answer

Chlorophyll absorbs violet-blue and red light, reflecting and transmitting green light

Question 5

Which enzyme catalyzes the initial fixation of CO$$_2 in $$the Calvin cycle?

Accepted Answer

Rubisco (RuBP carboxylase-oxygenase)

Question 6

In the Calvin cycle, for the net synthesis of one molecule of glyceraldehyde 3-phosphate (G3P), how many molecules of ATP and NADPH are consumed?

Accepted Answer

9 ATP and 6 NADPH

Question 7

Which of the following statements about cyclic electron flow in photosynthesis is correct?

Accepted Answer

It produces ATP but does not produce NADPH or oxygen

Question 8

What is the main advantage of C4 photosynthesis over C3 photosynthesis in hot, dry climates?

Accepted Answer

C4 plants minimize photorespiration by incorporating CO$$_2$$ into a four-carbon compound

Question 9

Which of the following best explains why photorespiration is considered an evolutionary relic?

Accepted Answer

Rubisco evolved when the atmosphere had less O$$_2$$ and more CO$$_2$$, making photorespiration less likely

Question 10

Which of the following is a correct comparison between chemiosmosis in chloroplasts and mitochondria?

Accepted Answer

In chloroplasts, protons are pumped into the thylakoid space; in mitochondria, protons are pumped into the intermembrane space

Question 11

Which molecule acts as the primary electron acceptor in the reaction center of a photosystem?

Accepted Answer

A specialized protein that accepts excited electrons from chlorophyll a

Question 12

What is the role of NADP+ reductase in the light reactions of photosynthesis?

Accepted Answer

It catalyzes the transfer of electrons from ferredoxin to NADP+, forming NADPH

Question 13

Which of the following wavelengths of light is most effective for photosynthesis according to the absorption spectrum of chlorophyll a?

Accepted Answer

Violet-blue and red

Question 14

A plant exposed to only green light would likely:

Accepted Answer

Have reduced photosynthetic activity because chlorophyll does not absorb green light efficiently

Question 15

Which of the following is a real-world consequence of rising atmospheric CO$$_2$$ levels for C3 and C4 plants?

Accepted Answer

C3 plants may benefit more from increased CO$$_2$$ than C4 plants, potentially changing their relative abundance

Question 16

Which adaptation allows CAM plants to conserve water in arid environments?

Accepted Answer

CAM plants open their stomata at night and fix CO$$_2$$ into organic acids

Question 17

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

Accepted Answer

The light reactions produce ATP and NADPH, which are used by the Calvin cycle to fix carbon

Question 18

Which of the following is a function of carotenoids in chloroplasts?

Accepted Answer

They absorb excessive light energy to protect chlorophyll from damage

Question 19

A scientist genetically modifies rice (a C3 plant) to carry out C4 photosynthesis. What is the most likely outcome?

Accepted Answer

Rice will have increased yield and use water more efficiently

Question 20

Which of the following is true about the spatial separation of carbon fixation in C4 plants?

Accepted Answer

Initial carbon fixation occurs in mesophyll cells, and the Calvin cycle occurs in bundle-sheath cells

Photosynthesis: Mechanisms, Adaptations, and Importance

Study Guide - Practice Questions