Question 1

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

Accepted Answer

C4 plants fix CO$$_2$$ into a 4-carbon compound in mesophyll cells, reducing photorespiration.

Question 2

A plant that opens its stomata only at night to minimize water loss is most likely a:

Accepted Answer

CAM plant

Question 3

Which of the following is a key adaptation of CAM plants that allows them to survive in arid environments?

Accepted Answer

They fix CO$$_2$$ into organic 4-carbon compounds during the night.

Question 4

In C4 plants, where does the Calvin cycle take place?

Accepted Answer

In the bundle-sheath cells

Question 5

Which of the following statements about photorespiration is correct?

Accepted Answer

Photorespiration occurs when rubisco binds O$$_2$$ instead of CO$$_2.$$

Question 6

A scientist discovers a plant that fixes CO$$_2$$ into a 4-carbon compound in the mesophyll cells and then transports it to bundle-sheath cells for the Calvin cycle. This plant is most likely a:

Accepted Answer

C4 plant

Question 7

Which of the following best describes the main difference between C3 and CAM plants in terms of CO$$_2$$ fixation?

Accepted Answer

C3 plants fix CO$$_2$$ during the day, while CAM plants fix CO$$_2 at $$night.

Question 8

Why do CAM plants keep their stomata closed during the day?

Accepted Answer

To reduce water loss through transpiration

Question 9

Which of the following is a disadvantage of the C3 pathway in hot, dry climates?

Accepted Answer

It is more susceptible to photorespiration, reducing photosynthetic efficiency.

Question 10

A plant is observed to have its Calvin cycle and light reactions occurring in the same cell, and it opens its stomata during the day. This plant is most likely a:

Accepted Answer

C3 plant

Question 11

Which of the following equations correctly represents the initial carbon fixation step in C4 plants?

Accepted Answer

$$\mathrm{CO_2$ + PEP \rightarrow Oxaloacetate}$$

Question 12

Which of the following best explains why C4 and CAM plants have evolved in hot, arid environments?

Accepted Answer

To minimize water loss and reduce photorespiration

Question 13

If a plant fixes CO$$_2 at $$night and stores it as an organic acid, which is then used during the day for the Calvin cycle, what type of plant is it?

Accepted Answer

CAM plant

Question 14

Which of the following is a correct sequence of events for carbon fixation in C4 plants?

Accepted Answer

CO$$_2 is $$fixed in the mesophyll cells, transported as a 4-carbon compound to bundle-sheath cells, and then enters the Calvin cycle.

Question 15

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

Accepted Answer

CO$$_2 is $$fixed in bundle-sheath cells

Question 16

A researcher is studying a plant that shows high rates of photorespiration under high temperatures. Which type of plant is it most likely to be?

Accepted Answer

C3 plant

Question 17

Which of the following best describes the main advantage of the C4 pathway over the C3 pathway?

Accepted Answer

C4 pathway reduces photorespiration by spatially separating initial CO$$_2$$ fixation and the Calvin cycle.

Question 18

Which of the following is a real-world example of a CAM plant?

Accepted Answer

Pineapple

Question 19

Which of the following statements is true regarding the Calvin cycle in C3, C4, and CAM plants?

Accepted Answer

The Calvin cycle occurs in the bundle-sheath cells in C4 plants.

Question 20

Which of the following best explains why photorespiration is considered wasteful for plants?

Accepted Answer

It consumes O$$_2$$ and releases CO$$_2$$ without producing ATP or sugars.

C3, C4, and CAM Plants: Photosynthetic Pathways and Adaptations

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