Photosynthesis Photosynthesis Pigments and Absorption 1 — Questions and Answers
Question 1: Which pigment primarily absorbs red and blue wavelengths of light during photosynthesis in plants?
- Chlorophyll a (Correct answer)
- Carotene
- Xanthophyll
- Phycocyanin
Correct answer: Chlorophyll a
Chlorophyll a is the primary photosynthetic pigment and absorbs light most strongly in the red (~680 nm) and blue (~430 nm) wavelengths.
Question 2: Why do most plant leaves appear green to the human eye?
- Chlorophyll reflects green wavelengths rather than absorbing them (Correct answer)
- Chlorophyll absorbs only green light
- Green light has the highest energy of all visible wavelengths
- Leaves contain more xanthophylls than chlorophyll
Correct answer: Chlorophyll reflects green wavelengths rather than absorbing them
Chlorophyll absorbs red and blue light for photosynthesis but reflects green wavelengths, which is what our eyes detect.
Question 3: What is the primary function of accessory pigments such as carotenoids and chlorophyll b in photosynthesis?
- Capture light energy from a broader range of wavelengths and transfer it to chlorophyll a (Correct answer)
- Directly reduce CO2 in the Calvin cycle
- Pump protons across the thylakoid membrane
- Break down water molecules to release oxygen
Correct answer: Capture light energy from a broader range of wavelengths and transfer it to chlorophyll a
Accessory pigments broaden the range of light wavelengths that can drive photosynthesis by absorbing energy and transferring it to chlorophyll a reaction centers.
Question 4: What is the approximate absorption peak of chlorophyll a in the red region of the visible spectrum?
- 680 nm (Correct answer)
- 500 nm
- 550 nm
- 750 nm
Correct answer: 680 nm
Chlorophyll a has a major absorption peak near 680 nm in the red region and another near 430 nm in the blue region.
Question 5: Which photosynthetic pigment is responsible for the orange color of carrots and also assists in harvesting light energy?
- Beta-carotene (Correct answer)
- Chlorophyll b
- Anthocyanin
- Phytochrome
Correct answer: Beta-carotene
Beta-carotene is a carotenoid pigment that gives carrots their orange color and also serves as an accessory pigment in plant photosynthesis.
Question 6: What is the name of the graph that plots the rate of photosynthesis against different wavelengths of light?
- Action spectrum (Correct answer)
- Absorption spectrum
- Emission spectrum
- Fluorescence spectrum
Correct answer: Action spectrum
The action spectrum shows which wavelengths are most effective at driving photosynthesis, and it closely mirrors the absorption spectrum of chlorophyll.
Photosynthesis Photosynthesis Pigments and Absorption 1
Which pigment primarily absorbs red and blue wavelengths of light during photosynthesis in plants?