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

Question 1

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

Accepted Answer

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

Question 2

What is the main function of chlorophyll a in photosynthesis?

Accepted Answer

It initiates the light-dependent reactions by absorbing light energy and transferring electrons.

Question 3

Why do leaves appear green to the human eye?

Accepted Answer

Chlorophyll reflects green light and absorbs red and blue light.

Question 4

Which structure within the chloroplast is the site of the light-dependent reactions?

Accepted Answer

Thylakoid membrane

Question 5

What is the primary role of the electron transport chain (ETC) in the thylakoid membrane during photosynthesis?

Accepted Answer

To generate a proton gradient that drives ATP synthesis

Question 6

Which of the following best explains why C4 and CAM plants are more efficient than C3 plants in hot, dry environments?

Accepted Answer

They minimize water loss and reduce photorespiration by altering the timing or location of carbon fixation.

Question 7

During the Calvin cycle, what is the first stable product formed when CO$$_2 is $$fixed?

Accepted Answer

A 3-carbon compound (3-phosphoglycerate, or 3-PGA)

Question 8

What is the main adaptive advantage of CAM photosynthesis?

Accepted Answer

It allows plants to fix carbon at night, reducing water loss during the day.

Question 9

Which pigment is primarily responsible for absorbing light in the blue and red regions of the visible spectrum?

Accepted Answer

Chlorophyll a

Question 10

What did T. W. Engelmann’s experiment demonstrate about photosynthesis?

Accepted Answer

Oxygen production during photosynthesis is highest in regions exposed to blue and red light.

Question 11

Which of the following is a direct product of the light-dependent reactions of photosynthesis?

Accepted Answer

ATP and NADPH

Question 12

Why does photorespiration occur more frequently in C3 plants under hot, dry conditions?

Accepted Answer

Stomata close to conserve water, leading to decreased CO$$_2$$ and increased O$$_2$$ inside the leaf.

Question 13

Which of the following best describes the role of accessory pigments such as carotenoids in photosynthesis?

Accepted Answer

They absorb wavelengths of light not absorbed by chlorophyll and transfer the energy to chlorophyll a.

Question 14

A plant is exposed only to green light. What is the most likely outcome for its rate of photosynthesis?

Accepted Answer

It will decrease because chlorophyll reflects green light.

Question 15

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

Accepted Answer

It uses ATP and NADPH to convert CO$$_2$$ into carbohydrates.

Question 16

What is the main reason why stomata close during hot, dry days?

Accepted Answer

To prevent excessive water loss through transpiration.

Question 17

Which of the following is NOT a phase of the Calvin cycle?

Accepted Answer

Oxygen evolution

Question 18

In which part of the leaf are most chloroplasts found, and why?

Accepted Answer

In the mesophyll cells, to maximize light absorption for photosynthesis.

Question 19

Which of the following best explains why visible light is effective for photosynthesis?

Accepted Answer

It has enough energy to cause reversible changes in chlorophyll molecules without damaging them.

Question 20

Which of the following is a correct description of the C4 pathway?

Accepted Answer

CO$$_2 is $$initially fixed into a 4-carbon compound in mesophyll cells, which is then transported to bundle sheath cells for the Calvin cycle.

Photosynthesis: Mechanisms, Structures, and Adaptations

Study Guide - Practice Questions