Question 1

Which enzyme is responsible for the fixation of carbon dioxide during the Calvin Cycle, and why is it considered significant in the biosphere?

Accepted Answer

Rubisco; it is the most abundant protein on Earth and catalyzes the incorporation of CO$$_2$$ into organic molecules.

Question 2

A mutation alters the structure of chlorophyll in Photosystem II. What is the most likely effect on the plant’s ability to perform photosynthesis?

Accepted Answer

The absorption peak of chlorophyll will shift, potentially reducing the efficiency of light capture.

Question 3

During the light reactions of photosynthesis, what is the primary role of the electron transport chain in the thylakoid membrane?

Accepted Answer

To create a proton (H$$^+) $$gradient used for ATP synthesis.

Question 4

Which of the following best describes the relationship between the light reactions and the Calvin Cycle in photosynthesis?

Accepted Answer

The light reactions supply ATP and NADPH to the Calvin Cycle, which uses them to fix CO$$_2$$ into sugars.

Question 5

How many molecules of ATP and NADPH are required to produce one molecule of glucose via the Calvin Cycle?

Accepted Answer

$$18$$ ATP and $$12$$ NADPH

Question 6

Which statement correctly compares the direction of the proton (H$$^+) $$gradient in photosynthesis and cellular respiration?

Accepted Answer

Photosynthesis pumps protons into the thylakoid lumen, while respiration pumps protons into the intermembrane space of mitochondria.

Question 7

A scientist discovers a bacterium that performs photosynthesis but does not produce oxygen. What is the best explanation for this observation?

Accepted Answer

The bacterium performs anoxygenic photosynthesis, using electron donors other than water.

Question 8

Which molecule acts as the initial electron donor in oxygenic photosynthesis, and what is the fate of the electrons?

Accepted Answer

H$$_2O$$; electrons are transferred through the electron transport chain to NADP$$^+$$, forming NADPH.

Question 9

Which of the following is a direct product of the Calvin Cycle that serves as a substrate for the synthesis of glucose and other organic molecules?

Accepted Answer

G3P (glyceraldehyde-3-phosphate)

Question 10

If a plant is exposed to light but deprived of CO$$_2$$, which of the following will occur?

Accepted Answer

The light reactions will produce ATP and NADPH, but the Calvin Cycle will halt due to lack of substrate.

Question 11

Which of the following is a similarity between cellular respiration and photosynthesis?

Accepted Answer

Both involve electron transport chains that generate a proton gradient for ATP synthesis.

Question 12

A plant cell is treated with a chemical that blocks ATP synthase in the thylakoid membrane. What is the most immediate effect?

Accepted Answer

ATP production during the light reactions will decrease, limiting sugar synthesis.

Question 13

Which of the following best explains why the absorption spectrum of chlorophyll a differs from that of chlorophyll b?

Accepted Answer

Differences in the structure and chemical environment of the pigment alter their absorption peaks.

Question 14

Which process occurs in the stroma of the chloroplast and uses ATP and NADPH generated by the light reactions?

Accepted Answer

Calvin Cycle

Question 15

In a scenario where a plant’s thylakoid membranes are damaged, which process would be most directly affected?

Accepted Answer

Production of ATP and NADPH during the light reactions

Question 16

Which of the following equations correctly represents the overall process of oxygenic photosynthesis?

Accepted Answer

$$6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + 	ext{light energy} ightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2$$

Question 17

Which of the following is NOT a product of the light reactions of photosynthesis?

Accepted Answer

Glucose

Question 18

If a plant is placed in an environment with no light, which of the following processes will be directly inhibited?

Accepted Answer

Light reactions (production of ATP and NADPH)

Question 19

Which of the following statements about Rubisco is TRUE?

Accepted Answer

Rubisco catalyzes the fixation of CO$$_2$$ into organic molecules in the Calvin Cycle.

Question 20

Which of the following best explains why photosynthesis is considered to be 'transforming the Earth'?

Accepted Answer

It converts atmospheric CO$$_2$$ into organic molecules, supporting most life forms and altering global carbon cycles.

Week 7 - Oct 24

Study Guide - Practice Questions