Q: Which equation correctly represents the overall process of photosynthesis?

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

Question 1

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

Accepted Answer

Photosynthesis converts light energy to chemical energy, producing organic molecules and oxygen, which are then used in cellular respiration to generate ATP and release heat energy.

Question 2

In the context of energy flow and chemical cycling (second image), what happens to most of the energy that enters an ecosystem as sunlight?

Accepted Answer

It is eventually lost from the ecosystem as heat after being used by organisms.

Question 3

Which equation correctly represents the overall process of photosynthesis?

Accepted Answer

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

Question 4

Based on the third and fourth images, what is the primary function of Photosystem II (PSII) in the light reactions?

Accepted Answer

To absorb light energy and split water, releasing oxygen and providing electrons for the electron transport chain.

Question 5

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

Accepted Answer

Both ATP and NADPH production would stop because water is the source of electrons for Photosystem II.

Question 6

Which structure in the chloroplast is directly responsible for the light-dependent reactions, as shown in the sixth image?

Accepted Answer

Thylakoid membrane

Question 7

Why are the light reactions called 'light-dependent'?

Accepted Answer

They require light energy to excite electrons in chlorophyll, initiating the production of ATP and NADPH.

Question 8

Which wavelengths of light are most effective for photosynthesis, according to the fifth image?

Accepted Answer

Blue (around 440 nm) and red (around 680 nm) wavelengths

Question 9

What is the main purpose of the Calvin cycle in photosynthesis?

Accepted Answer

To use ATP and NADPH to reduce CO$$_2$$ and synthesize sugars.

Question 10

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

Accepted Answer

Chloroplasts convert light energy to chemical energy, while mitochondria release energy from organic molecules 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

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

Question 12

Which molecule is reduced during photosynthesis?

Accepted Answer

CO$$_2$$

Question 13

How does the structure of the thylakoid membrane facilitate the light reactions?

Accepted Answer

It provides a large surface area for chlorophyll and electron transport proteins, enabling efficient light absorption and ATP/NADPH production.

Question 14

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

Accepted Answer

Increasing light intensity

Question 15

What is the role of ATP and NADPH in the Calvin cycle?

Accepted Answer

They provide energy and reducing power to convert CO$$_2$$ into G3P (a sugar intermediate).

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 the reduction of 3-PGA to G3P.

Question 17

Why do treated weeds show yellow leaves when exposed to a herbicide that disrupts the light reactions?

Accepted Answer

The herbicide causes chlorophyll breakdown due to impaired light reactions, reducing the plant's ability to absorb light and resulting in yellowing.

Question 18

Which of the following best describes the action spectrum of photosynthesis as shown in the fifth image?

Accepted Answer

Photosynthesis is most efficient in the blue and red regions, corresponding to the absorption peaks of chlorophyll a and b.

Question 19

Which process is responsible for returning chemicals to the soil in the ecosystem, as shown in the second image?

Accepted Answer

Decomposition by fungi and bacteria

Photosynthesis and Cellular Respiration: Interdependence and Mechanisms

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