Question 1

Which of the following is the correct sequence of steps in the Calvin cycle?

Accepted Answer

Carbon fixation, reduction, release of G3P, regeneration of RuBP

Question 2

During the Calvin cycle, what is the primary role of ATP?

Accepted Answer

To provide energy for the reduction of 3-phosphoglycerate to G3P

Question 3

Which enzyme catalyzes the first step of carbon fixation in the Calvin cycle?

Accepted Answer

Rubisco

Question 4

How many molecules of CO$$_2$$ are required to produce one molecule of G3P in the Calvin cycle?

Accepted Answer

$$3$$

Question 5

If a plant cell is exposed to a shortage of NADPH, which step of the Calvin cycle would be directly affected?

Accepted Answer

Reduction of 3-phosphoglycerate to G3P

Question 6

Which of the following best explains why C$$_4$$ and CAM plants are more efficient than C$$_3$$ plants in hot, dry climates?

Accepted Answer

They minimize photorespiration by initially fixing CO$$_2$$ into four-carbon compounds

Question 7

What is the net output of the Calvin cycle after three turns, assuming all necessary inputs are available?

Accepted Answer

One molecule of G3P

Question 8

Which of the following equations correctly represents the overall process of the Calvin cycle for the production 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 9

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

Accepted Answer

RuBP (ribulose bisphosphate)

Question 10

A scientist increases the concentration of CO$$_2 in a $$plant growth chamber. What is the most likely effect on the Calvin cycle?

Accepted Answer

The rate of carbon fixation will increase, leading to more G3P production

Question 11

Which of the following statements best describes the global significance of photosynthesis?

Accepted Answer

It provides food and oxygen for almost all living organisms on Earth

Question 12

If a mutation caused Rubisco to lose its ability to bind CO$$_2$$, which process would be directly affected?

Accepted Answer

Carbon fixation in the Calvin cycle

Question 13

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

Accepted Answer

G3P (glyceraldehyde-3-phosphate)

Question 14

Why does photorespiration occur more frequently in C$$_3$$ plants than in C$$_4 or $$CAM plants under hot, dry conditions?

Accepted Answer

C$$_3$$ plants do not have mechanisms to concentrate CO$$_2$$ around Rubisco, leading to increased oxygenation

Question 15

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

Accepted Answer

It donates electrons for the reduction of 3-phosphoglycerate to G3P

Question 16

A plant cell is unable to regenerate RuBP. What would be the immediate consequence for the Calvin cycle?

Accepted Answer

The cycle would stop because CO$$_2$$ could no longer be fixed

Question 17

Which of the following statements is true regarding the relationship between photosynthesis and cellular respiration in plants?

Accepted Answer

Cellular respiration uses about 50% of the carbohydrates made by photosynthesis

Question 18

Which of the following is a real-world consequence of rising atmospheric CO$$_2$$ levels for plant ecosystems?

Accepted Answer

Long-term field studies show changes in plant growth and ecosystem dynamics

Question 19

Cellulose, a major component of plant cell walls, is synthesized from which photosynthetic product?

Accepted Answer

Glucose molecules produced from G3P

Question 20

Which of the following best explains why no process is more important to the welfare of life on Earth than photosynthesis?

Accepted Answer

Photosynthesis provides the food and oxygen necessary for almost all living organisms

The Calvin Cycle and Photosynthesis: Mechanisms, Adaptations, and Global Significance

Study Guide - Practice Questions