Photosynthesis Calvin Cycle 3

Question 1

How does photorespiration differ from the Calvin cycle in terms of RuBisCO activity?

Accepted Answer

RuBisCO fixes O₂ instead of CO₂, releasing CO₂ and wasting energy

Answer

RuBisCO is inactive during photorespiration

Answer

RuBisCO produces extra G3P during photorespiration

Answer

Photorespiration regenerates RuBP faster

Question 2

C4 plants minimize photorespiration primarily by doing what?

Accepted Answer

Concentrating CO₂ around RuBisCO in bundle sheath cells

Answer

Running the Calvin cycle in mesophyll cells only

Answer

Eliminating RuBisCO entirely

Answer

Using a different carboxylase that ignores O₂

Question 3

What is the net output of the Calvin cycle per 3 CO₂ fixed?

Accepted Answer

One G3P, 9 ATP consumed, 6 NADPH consumed

Answer

One G3P, 3 ATP consumed, 3 NADPH consumed

Answer

Two G3P, 6 ATP consumed, 6 NADPH consumed

Answer

One glucose, 6 ATP consumed, 6 NADPH consumed

Question 4

Which of the following best describes the role of ATP in the regeneration phase of the Calvin cycle?

Accepted Answer

It phosphorylates ribulose-5-phosphate to form RuBP

Answer

It reduces 1,3-bisphosphoglycerate to G3P

Answer

It carboxylates RuBP

Answer

It oxidizes NADPH to NADP⁺

Question 5

If a plant is exposed to radioactive ¹⁴CO₂ and illuminated for only 2 seconds, which compound would first become labeled?

Accepted Answer

3-PGA

Answer

G3P

Answer

RuBP

Answer

Glucose

Question 6

CAM plants open their stomata at night to take in CO₂ primarily to:

Accepted Answer

Store CO₂ as malate and release it for the Calvin cycle during the day

Answer

Run the Calvin cycle in darkness

Answer

Avoid photorespiration by using a different pathway at night

Answer

Increase oxygen uptake for mitochondrial respiration

Question 7

What is the correct ratio of ATP to NADPH required per CO₂ fixed in the Calvin cycle?

Accepted Answer

3:2

Answer

1:1

Answer

2:1

Answer

2:3