Q: Which of the following equations correctly represents the overall process of oxygenic 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 statements best describes the difference between autotrophs and heterotrophs?

Accepted Answer

Autotrophs produce O$$_2$$ and carbohydrates from CO$$_2$$ and H$$_2O$$, while heterotrophs consume carbohydrates and O$$_2.$$

Question 2

What is the primary role of chlorophyll a in photosynthesis?

Accepted Answer

To contain a porphyrin ring with Mg and absorb light maximally at 680 nm.

Question 3

Which of the following molecules is NOT an accessory pigment in photosynthesis?

Accepted Answer

Chlorophyll a

Question 4

Why do plants appear green to the human eye?

Accepted Answer

They reflect green light, which is not absorbed by chlorophyll.

Question 5

Which of the following best explains the difference between the absorption spectrum and the action spectrum of photosynthesis?

Accepted Answer

The absorption spectrum shows the wavelengths of light absorbed by pigments, while the action spectrum shows the relative effectiveness of different wavelengths in driving photosynthesis.

Question 6

Given the absorption spectrum of chlorophyll a, at which wavelength would you expect the highest rate of photosynthetic activity?

Accepted Answer

Around 680 nm

Question 7

Which structural feature of chlorophyll a is essential for its light-absorbing properties?

Accepted Answer

A porphyrin ring with a central Mg ion

Question 8

If a plant lacked carotenoids, what would be the most likely consequence?

Accepted Answer

It would have a reduced ability to broaden the absorption spectrum and protect against photooxidative damage.

Question 9

Which of the following best describes the function of accessory pigments in photosynthesis?

Accepted Answer

They absorb light in regions where chlorophyll a absorbs poorly and transfer energy to chlorophyll a.

Question 10

A researcher measures the action spectrum of a plant and finds two peaks, one in the blue region (around 450 nm) and one in the red region (around 680 nm). What does this suggest about the plant's pigments?

Accepted Answer

The plant contains pigments that absorb both blue and red light, such as chlorophyll a and b.

Question 11

Which of the following equations correctly represents the overall process of oxygenic 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 12

Which pigment is primarily responsible for the absorption peak at around 450 nm in the absorption spectrum?

Accepted Answer

Chlorophyll a

Question 13

A mutation causes a plant to lack chlorophyll b. What is the most likely effect on the plant's photosynthetic efficiency?

Accepted Answer

The plant's absorption spectrum will be narrower, reducing its ability to utilize light energy efficiently.

Question 14

Which of the following best explains why the action spectrum of photosynthesis does not exactly match the absorption spectrum of chlorophyll a?

Accepted Answer

Accessory pigments transfer absorbed energy to chlorophyll a, enhancing photosynthetic activity at wavelengths where chlorophyll a absorbs poorly.

Question 15

Which of the following is a direct product of the light-dependent reactions of photosynthesis?

Accepted Answer

ATP

Photosynthesis and Photophosphorylation: Pigments and Light Absorption

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