Question 1

Which of the following best describes the relationship between photosynthesis and cellular respiration in the ecosystem, as shown in the first diagram?

Accepted Answer

Photosynthesis transforms light energy into organic molecules, which are then broken down by cellular respiration to produce ATP.

Question 2

According to the second diagram, what is the primary fate of light energy entering an ecosystem?

Accepted Answer

It is converted by plants into chemical energy, which is then used by organisms and eventually lost as heat.

Question 3

In the third diagram, which molecule is oxidized during the light reactions of photosynthesis?

Accepted Answer

H$$_2O$$

Question 4

Based on the fourth diagram, what is the immediate source of electrons for Photosystem II (PSII)?

Accepted Answer

Water ($$H_2O)$$

Question 5

Referencing the fifth diagram, which wavelengths of light are most effective for photosynthesis?

Accepted Answer

Blue (430–455 nm) and red (640–680 nm)

Question 6

In the sixth diagram, what is the main purpose of the Calvin cycle?

Accepted Answer

To convert ATP and NADPH into sugars by reducing $$CO_2$$

Question 7

Which structure in the chloroplast is directly involved in the light reactions, as shown in the diagrams?

Accepted Answer

Thylakoid membrane

Question 8

What would happen to ATP and NADPH production if water were not available to the chloroplast?

Accepted Answer

Both ATP and NADPH production would decrease because water is needed to supply electrons to Photosystem II.

Question 9

How does the structure of the thylakoid membrane facilitate the production of ATP during the light reactions?

Accepted Answer

It creates a proton gradient by separating the stroma and thylakoid lumen, enabling ATP synthase to convert ADP and $$P_i$$ into ATP.

Question 10

Which of the following best explains why plants need both chloroplasts and mitochondria?

Accepted Answer

Chloroplasts capture light energy to make sugars, while mitochondria break down sugars to produce ATP for cellular work.

Question 11

If an herbicide blocks electron flow between Photosystem II and Photosystem I, what would be the effect on ATP and NADPH levels?

Accepted Answer

Both ATP and NADPH levels would decrease because electron transport is required for their synthesis.

Question 12

Which environmental factor would most likely increase the rate of the light reactions up to a certain point, then plateau?

Accepted Answer

Increasing light intensity

Question 13

Why is the Calvin cycle considered an anabolic pathway?

Accepted Answer

It synthesizes sugars from $$CO_2$$, using energy from ATP and NADPH.

Question 14

What is the role of NADP$$^+$$ reductase in the light reactions?

Accepted Answer

It transfers electrons to NADP$$^+$$, forming NADPH.

Question 15

Which of the following is a correct summary of the overall photosynthesis equation?

Accepted Answer

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

Question 16

If the supply of NADPH were interrupted, what would happen to the Calvin cycle?

Accepted Answer

The Calvin cycle would slow down or stop because NADPH is required for reduction of $$CO_2.$$

Question 17

How does temperature affect the rate of the Calvin cycle reactions?

Accepted Answer

There is an optimal temperature range; outside this range, the rate decreases due to enzyme denaturation or reduced activity.

Question 18

What is the main function of ATP synthase in the light reactions?

Accepted Answer

To use the proton gradient to synthesize ATP from ADP and $$P_i.$$

Question 19

Which of the following best explains why treated weeds show yellow leaves after exposure to HerbiClear-27?

Accepted Answer

The herbicide disrupts the light reactions, reducing chlorophyll content and causing loss of green color.

Photosynthesis and Cellular Respiration Study Guide

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