Question 1

Which of the following statements best explains why plants release oxygen during photosynthesis?

Accepted Answer

Oxygen is released when water is split to provide electrons for photosystem II.

Question 2

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

Accepted Answer

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Question 3

A scientist uses $$H_2$$^{18}O$$ (water labeled with the heavy isotope $$^{18}O$$) in a photosynthesis experiment. Which product will contain the $$^{18}O$$ label?

Accepted Answer

Oxygen gas ($$O_2)$$

Question 4

Which of the following best describes the role of chlorophyll in photosynthesis?

Accepted Answer

Chlorophyll absorbs light energy, exciting electrons that are transferred to the reaction center.

Question 5

Why is the color green least effective at driving photosynthesis in plants?

Accepted Answer

Green light is reflected and transmitted by chlorophyll rather than absorbed.

Question 6

Which of the following is a correct sequence of events in the light reactions of photosynthesis?

Accepted Answer

Splitting of water → electron transport chain → formation of NADPH

Question 7

During the Calvin cycle, which molecule is directly produced and can be used to synthesize glucose and other organic molecules?

Accepted Answer

Glyceraldehyde-3-phosphate (G3P)

Question 8

Which of the following best explains why two photons of light are required to move electrons from water to NADP+ during the light reactions?

Accepted Answer

One photon excites electrons in photosystem II, and a second photon excites electrons in photosystem I, allowing the electrons to reach a high enough energy to reduce NADP+.

Question 9

Which of the following statements about the electron transport chain in the thylakoid membrane is correct?

Accepted Answer

It pumps $$H^+$$ ions into the thylakoid space, creating a gradient used to synthesize ATP.

Question 10

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

Accepted Answer

Glucose ($$C_6H_{12}O_6$)

Question 11

A plant is placed in an environment with no light but is supplied with ATP and NADPH. Which stage of photosynthesis can still proceed under these conditions?

Accepted Answer

The Calvin cycle

Question 12

Which of the following best describes the greenhouse effect?

Accepted Answer

The trapping of heat by atmospheric gases such as $$CO_2$$, which warms the Earth's surface.

Question 13

Which of the following is a real-world consequence of deforestation on the global carbon cycle?

Accepted Answer

It reduces the removal of $$CO_2$$ from the atmosphere, contributing to climate change.

Question 14

Which of the following statements about autotrophs and heterotrophs is correct?

Accepted Answer

Photoautotrophs use light energy to synthesize organic molecules from inorganic substances.

Question 15

Which of the following best explains why intact chloroplasts do not emit heat and light when illuminated, unlike isolated chlorophyll solutions?

Accepted Answer

In intact chloroplasts, the energy from excited electrons is transferred to the electron transport chain rather than being released as heat and light.

Question 16

Which of the following is the main source of mass for the carbohydrates produced by plants during photosynthesis?

Accepted Answer

Carbon dioxide absorbed from the air

Question 17

Which of the following is an example of a redox reaction in photosynthesis?

Accepted Answer

The reduction of $$CO_2 to $$form glucose

Question 18

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

Accepted Answer

The light reactions produce ATP and NADPH, which are used in the Calvin cycle to fix carbon dioxide.

Question 19

Which of the following is a direct effect of increased atmospheric $$CO_2 on $$plant growth, as observed in long-term field studies?

Accepted Answer

Some species, such as poison ivy, may grow faster and become more toxic.

Question 20

Which of the following statements about the fate of sugars produced by photosynthesis in plants is correct?

Accepted Answer

Sugars can be used for cellular respiration, as building blocks for other molecules, or stored as starch.

Photosynthesis: Using Light to Make Food – Study Notes

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