Question 1

Which of the following best describes the main difference between autotrophs and heterotrophs in an ecosystem?

Accepted Answer

Autotrophs use inorganic materials and an energy source to make organic molecules, while heterotrophs must obtain organic molecules by eating other organisms or their products.

Question 2

The overall equation for photosynthesis is given by:

$$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

In $$this equation, what is the source of the oxygen gas ($$\mathrm{O}_2) $$released during photosynthesis?

Accepted Answer

It is produced by the splitting of water ($$\mathrm{H}_2\mathrm{O}) $$molecules during the light reactions.

Question 3

Which of the following correctly matches the location and main function of the light reactions in photosynthesis?

Accepted Answer

Location: thylakoid membranes; Function: convert light energy into ATP and NADPH, releasing $$\mathrm{O}_2$$ from water

Question 4

A plant is exposed to a toxin that specifically inhibits ATP synthase in the thylakoid membrane. Which of the following processes would be directly affected?

Accepted Answer

The production of ATP by chemiosmosis during the light reactions

Question 5

Which statement best explains why C4 and CAM plants are better adapted to hot, dry environments compared to C3 plants?

Accepted Answer

C4 and CAM plants have mechanisms to concentrate $$\mathrm{CO}_2$$ near rubisco or fix $$\mathrm{CO}_2 at $$night, reducing photorespiration.

Question 6

During the light reactions, electrons follow a path from water to NADP$$^+. $$Which of the following correctly traces the general path of these electrons?

Accepted Answer

Water $$\rightarrow$$ Photosystem II $$\rightarrow$$ Electron Transport Chain $$\rightarrow$$ Photosystem I $$\rightarrow$$ NADP$$^+$$

Question 7

Which of the following best describes the role of accessory pigments such as chlorophyll b and carotenoids in photosynthesis?

Accepted Answer

They broaden the spectrum of light that can be absorbed and help protect the plant from excess light.

Question 8

A scientist compares chemiosmosis in chloroplasts and mitochondria. Which of the following is a correct distinction between the two?

Accepted Answer

In chloroplasts, H$$^+$$ accumulates in the thylakoid space, while in mitochondria, H$$^+$$ accumulates in the intermembrane space.

Question 9

Which of the following is NOT a phase of the Calvin cycle?

Accepted Answer

Splitting of water

Question 10

Photorespiration is considered wasteful for plants because:

Accepted Answer

Rubisco binds $$\mathrm{O}_2$$ instead of $$\mathrm{CO}_2$$, consuming resources without producing sugar.

Question 11

Which of the following statements correctly compares ATP and NADPH in the context of photosynthesis?

Accepted Answer

ATP supplies usable energy, while NADPH donates high-energy electrons (reducing power) to the Calvin cycle.

Question 12

A mutation causes a plant's rubisco enzyme to lose its ability to bind $$\mathrm{CO}_2. $$Which immediate effect would this have on the Calvin cycle?

Accepted Answer

The plant would be unable to fix carbon, halting the production of G3P and sugars.

Question 13

Which of the following best explains why photosynthesis is essential for life on Earth?

Accepted Answer

It supplies organic molecules that support food webs and releases oxygen for aerobic respiration.

Question 14

A plant is placed in an environment with no light but with an abundance of $$\mathrm{CO}_2$$ and water. Which of the following will most likely occur?

Accepted Answer

The plant will be unable to perform the light reactions, so the Calvin cycle will also stop.

Question 15

Which of the following is a real-world example of how the endosymbiotic theory is supported by the structure of chloroplasts?

Accepted Answer

Chloroplasts contain their own circular DNA and double membranes, similar to free-living photosynthetic bacteria.

Question 16

If a plant's thylakoid membranes were damaged, which of the following would be the most immediate consequence?

Accepted Answer

The plant would be unable to generate a proton gradient, halting ATP and NADPH production in the light reactions.

Question 17

Which of the following best describes the function of ATP synthase in the chloroplast?

Accepted Answer

It uses the flow of H$$^+$$ ions from the thylakoid space into the stroma to produce ATP.

Question 18

A researcher is studying a plant that keeps its stomata closed during the day and opens them at night to fix $$\mathrm{CO}_2. $$This plant most likely uses which photosynthetic adaptation?

Accepted Answer

CAM photosynthesis

Question 19

Which of the following is a correct comparison between the light reactions and the Calvin cycle?

Accepted Answer

The light reactions produce ATP and NADPH, while the Calvin cycle uses them to fix $$\mathrm{CO}_2.$$

Question 20

A leaf cell is observed to have a high concentration of G3P. Which phase of the Calvin cycle has just occurred, and what is the significance of G3P?

Accepted Answer

Reduction phase; G3P is a three-carbon sugar precursor that can be used to make glucose and other organic molecules.

Chapter 8: Photosynthesis – Structure, Function, and Importance

Guida di studio - Domande di pratica

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