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

Question 1

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

Accepted Answer

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

Question 2

Which organelle is primarily responsible for photosynthesis in plant cells?

Accepted Answer

Chloroplast

Question 3

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

Accepted Answer

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

Question 4

Which pigment is the primary light-capturing molecule in chloroplasts?

Accepted Answer

Chlorophyll a

Question 5

During the light reactions, what is the source of electrons for the electron transport chain?

Accepted Answer

H$$_2O$$

Question 6

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

Accepted Answer

It involves only Photosystem I and produces ATP but not NADPH or O$$_2$$

Question 7

What is the role of ATP synthase in the thylakoid membrane during photosynthesis?

Accepted Answer

It couples the diffusion of H$$^+$$ down its gradient to the phosphorylation of ADP to ATP

Question 8

Which phase of the Calvin cycle involves the enzyme rubisco catalyzing the fixation of CO$$_2$$?

Accepted Answer

Carbon fixation

Question 9

In C$$_4$$ plants, what is the initial product of CO$$_2$$ fixation?

Accepted Answer

A four-carbon compound

Question 10

Which enzyme in C$$_4$$ plants has a higher affinity for CO$$_2$$ than rubisco and helps minimize photorespiration?

Accepted Answer

PEP carboxylase

Question 11

What is the main adaptive advantage of CAM photosynthesis in plants?

Accepted Answer

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

Question 12

Which of the following best explains why most leaves appear green?

Accepted Answer

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

Question 13

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

Accepted Answer

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

Question 14

Photorespiration is considered wasteful because:

Accepted Answer

It consumes O$$_2$$ and organic fuel without producing ATP or sugar

Question 15

Which of the following is true about the action spectrum for photosynthesis?

Accepted Answer

It is broader than the absorption spectrum of chlorophyll a due to accessory pigments

Question 16

If a plant is exposed only to green light, what would you expect to happen to its rate of photosynthesis?

Accepted Answer

It would decrease because green light is least effective for photosynthesis

Question 17

Which of the following is the first step in the light reactions of photosynthesis?

Accepted Answer

A photon excites an electron in a pigment molecule of Photosystem II

Question 18

What is the net consumption of ATP and NADPH for the synthesis of one G3P molecule in the Calvin cycle?

Accepted Answer

$$9 	ext{ ATP}, 6 	ext{ NADPH}$$

Question 19

Which of the following is a real-world consequence of rising atmospheric CO$$_2$$ for C$$_3$$ and C$$_4$$ plants?

Accepted Answer

Increasing CO$$_2$$ may change the relative abundance of C$$_3$$ and C$$_4$$ species, with unpredictable effects on agriculture

Question 20

Which of the following best describes the difference between C$$_4$$ and CAM photosynthesis?

Accepted Answer

C$$_4$$ separates carbon fixation and the Calvin cycle in space; CAM separates them in time

Photosynthesis: The Process That Powers the Biosphere

Study Guide - Practice Questions