Q: What is the overall balanced chemical equation for photosynthesis?

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

Question 1

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

Accepted Answer

It absorbs visible light energy, which excites electrons used to drive the light reactions.

Question 2

What is the overall balanced chemical equation for 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 3

Which color of visible light is least effective at driving photosynthesis, and why?

Accepted Answer

Green, because it is mostly reflected rather than absorbed by chlorophyll.

Question 4

During the light reactions of photosynthesis, what is the primary function of water?

Accepted Answer

It donates electrons to replace those lost by chlorophyll in photosystem II, producing oxygen as a byproduct.

Question 5

Which of the following statements about chemiosmosis in chloroplasts is correct?

Accepted Answer

A proton gradient across the thylakoid membrane drives ATP synthesis via ATP synthase.

Question 6

What is the main product of the Calvin cycle that can be used to synthesize glucose and other organic molecules?

Accepted Answer

Glyceraldehyde-3-phosphate (G3P)

Question 7

Which adaptation allows C4 plants to minimize photorespiration in hot, dry climates?

Accepted Answer

Spatial separation of carbon fixation and the Calvin cycle in different cell types.

Question 8

Why is photorespiration considered a wasteful process for plants?

Accepted Answer

It consumes oxygen and organic fuel, releases carbon dioxide, and produces no sugar.

Question 9

Which of the following best explains the global significance of photosynthesis?

Accepted Answer

It provides food and oxygen for almost all living organisms and helps moderate climate change by removing $$\mathrm{CO}_2$$ from the atmosphere.

Question 10

Which of the following is a correct description of the flow of electrons during the light reactions of photosynthesis?

Accepted Answer

Electrons flow from water to NADP$$^+$$, forming NADPH.

Question 11

A plant is exposed to light that is only in the green wavelength range. What is the most likely outcome for the rate of photosynthesis?

Accepted Answer

The rate of photosynthesis will decrease because green light is mostly reflected, not absorbed.

Question 12

Which process in photosynthesis is directly responsible for the production of oxygen gas ($$\mathrm{O}_2$$)?

Accepted Answer

The splitting of water molecules during the light reactions.

Question 13

Which of the following best describes the greenhouse effect as it relates to photosynthesis and climate change?

Accepted Answer

$$\mathrm{CO}_2$$ and other gases trap heat in the atmosphere, and photosynthesis helps reduce $$\mathrm{CO}_2$$ levels, potentially moderating climate change.

Question 14

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

Accepted Answer

Glucose

Question 15

How do the reactant molecules of photosynthesis reach the chloroplasts in leaves?

Accepted Answer

Carbon dioxide enters through stomata, and water is absorbed by roots and transported via xylem.

Question 16

Which of the following best explains why CAM plants are adapted to arid environments?

Accepted Answer

They open their stomata at night to minimize water loss and store $$\mathrm{CO}_2 as $$malic acid.

Question 17

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

Accepted Answer

It uses ATP and NADPH produced in the light reactions to fix carbon dioxide into G3P.

Question 18

Which of the following is a correct comparison between autotrophs and heterotrophs?

Accepted Answer

Autotrophs produce their own food using inorganic molecules, while heterotrophs consume organic material for energy.

Question 19

A scientist uses radioactive oxygen ($$^{18}\mathrm{O}) to $$trace the path of oxygen atoms during photosynthesis. If the plant is supplied with $$\mathrm{H}_2$$^{18}$$\mathrm{O}$$, where will the radioactive oxygen be found at the end of the light reactions?

Accepted Answer

In the oxygen gas ($$\mathrm{O}_2) $$released by the plant.

Chapter 7: Photosynthesis – Using Light to Make Food

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