Question 1

Which of the following best explains why C4 and CAM plants have evolved alternative mechanisms of carbon fixation compared to C3 plants?

Accepted Answer

They minimize photorespiration and water loss in hot, arid climates.

Question 2

In C4 plants, where does the initial fixation of CO$$_2$$ occur, and what is the primary enzyme involved?

Accepted Answer

Mesophyll cells; PEP carboxylase

Question 3

Which equation correctly represents the overall process of photosynthesis?

Accepted Answer

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

Question 4

Why do CAM plants open their stomata at night instead of during the day?

Accepted Answer

To reduce water loss due to evaporation.

Question 5

Which of the following statements about photorespiration is correct?

Accepted Answer

Photorespiration occurs when Rubisco fixes O$$_2$$ instead of CO$$_2.$$

Question 6

A scientist is studying a plant that fixes CO$$_2 at $$night and stores it as an organic acid. During the day, the CO$$_2 is $$released for use in the Calvin cycle. What type of plant is this?

Accepted Answer

CAM plant

Question 7

Which adaptation allows C4 plants to thrive in hot, dry environments?

Accepted Answer

They separate initial CO$$_2$$ fixation and the Calvin cycle into different cell types.

Question 8

What is the main advantage of the C4 pathway over the C3 pathway in terms of photosynthetic efficiency?

Accepted Answer

C4 pathway reduces photorespiration by concentrating CO$$_2$$ around Rubisco.

Question 9

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

Accepted Answer

It fixes carbon dioxide during the Calvin cycle.

Question 10

A plant is found to have high rates of photorespiration and low photosynthetic efficiency under hot, dry conditions. Which type of plant is this most likely to be?

Accepted Answer

C3 plant

Question 11

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

Accepted Answer

ATP

Question 12

If a plant closes its stomata during the day to conserve water, which process is most likely to be affected?

Accepted Answer

Uptake of CO$$_2$$

Question 13

Which of the following is NOT a characteristic of CAM plants?

Accepted Answer

They separate CO$$_2$$ fixation and the Calvin cycle into different cell types.

Question 14

Which process is responsible for the release of oxygen during photosynthesis?

Accepted Answer

Splitting of water molecules during the light reactions

Question 15

A researcher observes that a plant has Kranz anatomy. What does this indicate about the plant's photosynthetic pathway?

Accepted Answer

It uses the C4 pathway.

Alternative Mechanisms of Carbon Fixation and the Importance of Photosynthesis

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