Question 1

Which enzyme is directly responsible for the fixation of carbon dioxide in the Calvin cycle?

Accepted Answer

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

Question 2

During Melvin Calvin's experiments, which technique was used to identify the metabolic intermediates of the Calvin cycle?

Accepted Answer

Paper chromatography with radioactive labeling

Question 3

What is the primary product that exits the Calvin cycle after three turns, and how many carbon atoms does it contain?

Accepted Answer

Glyceraldehyde-3-phosphate (G3P, 3C)

Question 4

Which of the following best describes the role of ATP and NADPH in the Calvin cycle?

Accepted Answer

They provide energy and reducing power for the reduction of 3-phosphoglycerate to G3P

Question 5

If a plant cell is exposed to $$^{14}CO$_2$$ and then analyzed after 5 seconds, which Calvin cycle intermediate is most likely to be radiolabeled first?

Accepted Answer

3-phosphoglycerate (3-PGA)

Question 6

Which phase of the Calvin cycle involves the conversion of 3-phosphoglycerate into G3P?

Accepted Answer

Reduction

Question 7

Why do the light reactions of photosynthesis generate excess ATP via cyclic pathways?

Accepted Answer

Because the Calvin cycle requires more ATP than NADPH

Question 8

Which of the following correctly describes the location of the Calvin cycle within the chloroplast?

Accepted Answer

In the stroma, outside the thylakoids

Question 9

How many molecules of CO$$_2$$ must enter the Calvin cycle to produce one molecule of G3P?

Accepted Answer

Three

Question 10

Which of the following is regenerated at the end of the Calvin cycle to allow the cycle to continue?

Accepted Answer

Ribulose-1,5-bisphosphate (RuBP)

Question 11

A mutation disables rubisco in a plant. What immediate effect would this have on the Calvin cycle?

Accepted Answer

CO$$_2$$ would not be fixed to RuBP, halting the cycle

Question 12

Which of the following best explains why the Calvin cycle is considered a 'cycle'?

Accepted Answer

It regenerates its starting molecule, RuBP, after each turn

Question 13

In the context of the food chain, what is the primary ecological role of the Calvin cycle?

Accepted Answer

To convert inorganic carbon into organic compounds for energy

Question 14

Which of the following equations correctly represents the overall chemical change during the Calvin cycle for the synthesis of one G3P molecule?

Accepted Answer

$$3 \mathrm{CO}_2 + 9 \mathrm{ATP} + 6 \mathrm{NADPH} \rightarrow 1 \mathrm{G3P} + 9 \mathrm{ADP} + 8 \mathrm{P_i} + 6 \mathrm{NADP}^+$$

Question 15

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

Accepted Answer

Reduction uses ATP and NADPH to convert 3-phosphoglycerate to G3P

Question 16

If a plant is unable to regenerate RuBP, which step of the Calvin cycle would be directly affected?

Accepted Answer

Carbon fixation

Question 17

Which of the following is a direct consequence of the Calvin cycle for global carbon cycling?

Accepted Answer

It converts atmospheric CO$$_2$$ into organic compounds

Question 18

In a scenario where a plant receives sunlight but no CO$$_2$$, which process would be most directly affected?

Accepted Answer

Calvin cycle

Question 19

Which of the following best describes the relationship between the light reactions and the Calvin cycle?

Accepted Answer

The light reactions provide ATP and NADPH for the Calvin cycle

Photosynthesis and the Calvin Cycle: Mechanisms and Experimental Discovery

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