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

Question 1

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

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 2

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

Accepted Answer

To convert light energy into chemical energy stored in ATP and NADPH

Question 3

Which pigment is primarily responsible for the green color of plants and the absorption of light energy during photosynthesis?

Accepted Answer

Chlorophyll

Question 4

Why do plants appear green to the human eye?

Accepted Answer

Chlorophyll reflects and transmits green wavelengths of light

Question 5

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

Accepted Answer

It uses ATP and NADPH produced in the light reactions to reduce CO$$_2 to $$sugar

Question 6

What is the role of water in the light-dependent reactions of photosynthesis?

Accepted Answer

It donates electrons to replace those lost by chlorophyll in photosystem II

Question 7

Which enzyme catalyzes the fixation of CO$$_2 in $$the Calvin cycle and is considered the most abundant enzyme on Earth?

Accepted Answer

Rubisco (Ribulose-1,5-bisphosphate carboxylase/oxygenase)

Question 8

Why is photorespiration considered wasteful for plants?

Accepted Answer

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

Question 9

Which process best explains how ATP is produced during the light reactions of photosynthesis?

Accepted Answer

Photophosphorylation, where a proton gradient drives ATP synthase

Question 10

In C$$_4$$ plants, what is the main advantage of spatially separating initial CO$$_2$$ fixation from the Calvin cycle?

Accepted Answer

It minimizes photorespiration by concentrating CO$$_2$$ around rubisco

Question 11

Which of the following best describes the Z scheme in photosynthesis?

Accepted Answer

It is a model showing the flow of electrons from water through photosystem II and I to NADP$$^+$$

Question 12

Which molecule acts as the terminal electron acceptor in the noncyclic electron flow of photosynthesis?

Accepted Answer

NADP$$^+$$

Question 13

What is the main function of carotenoids in the thylakoid membranes?

Accepted Answer

They absorb light energy and protect chlorophyll from damage by stabilizing free radicals

Question 14

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 spatially, while CAM plants separate them temporally

Question 15

A scientist exposes isolated chloroplasts to only red light, only far-red light, and both together. What result supports the enhancement effect?

Accepted Answer

Photosynthesis rate is highest when both red and far-red light are present

Question 16

Which of the following best explains why shorter wavelengths of light have more energy than longer wavelengths?

Accepted Answer

The energy of a photon is inversely proportional to its wavelength: $$E = \frac{hc}{\lambda}$$

Question 17

Which of the following is a direct product of the Calvin cycle that can be used to synthesize glucose and other carbohydrates?

Accepted Answer

Glyceraldehyde-3-phosphate (G3P)

Question 18

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

Accepted Answer

To prevent water loss through evaporation

Question 19

Which of the following best describes the fate of oxygen atoms from water molecules during oxygenic photosynthesis?

Accepted Answer

They are released as O$$_2$$ gas

Question 20

Which process is responsible for the regeneration of RuBP in the Calvin cycle?

Accepted Answer

The third phase of the Calvin cycle, which uses ATP to regenerate RuBP from G3P

Chapter 10: Photosynthesis – Mechanisms and Significance

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