BioInteractive Photosynthetic Pigments and Light Absorption 1 — Questions and Answers
Question 1: Which wavelengths of light does chlorophyll a absorb most strongly?
- Blue (~430 nm) and red (~662 nm) (Correct answer)
- Green (500–560 nm)
- UV (< 400 nm)
- Infrared (> 700 nm)
Correct answer: Blue (~430 nm) and red (~662 nm)
Chlorophyll a has strong absorption peaks in the blue and red portions of the visible spectrum.
Question 2: What is the role of accessory pigments such as carotenoids in photosynthesis?
- Absorb additional wavelengths of light and transfer energy to chlorophyll (Correct answer)
- Directly synthesize ATP
- Fix carbon dioxide
- Split water molecules
Correct answer: Absorb additional wavelengths of light and transfer energy to chlorophyll
Accessory pigments extend the range of light wavelengths captured and funnel that energy to the chlorophyll reaction centers.
Question 3: Why do leaves appear green to human eyes?
- Chlorophyll reflects green wavelengths while absorbing red and blue (Correct answer)
- Chlorophyll absorbs green light only
- Leaves contain mostly carotenoids
- Green light has the most energy
Correct answer: Chlorophyll reflects green wavelengths while absorbing red and blue
Chlorophyll absorbs red and blue light for photosynthesis but reflects green light, which is what we see.
Question 4: What is an action spectrum in the context of photosynthesis?
- A graph showing the rate of photosynthesis at different wavelengths of light (Correct answer)
- A graph of chlorophyll absorption
- A diagram of ATP production
- A chart of CO2 fixation rates
Correct answer: A graph showing the rate of photosynthesis at different wavelengths of light
An action spectrum plots the rate of photosynthesis against wavelengths of light, showing which wavelengths drive the most photosynthetic activity.
Question 5: Which pigment is responsible for the yellow and orange colors seen in autumn leaves?
- Carotenoids (Correct answer)
- Chlorophyll b
- Phycocyanin
- Anthocyanin
Correct answer: Carotenoids
Carotenoids (carotenes and xanthophylls) produce yellow and orange colors that become visible when chlorophyll breaks down in autumn.
Question 6: What technique is commonly used to separate photosynthetic pigments in a laboratory?
- Paper or thin-layer chromatography (Correct answer)
- Gel electrophoresis
- Western blotting
- PCR
Correct answer: Paper or thin-layer chromatography
Chromatography separates pigments based on their solubility and interaction with the stationary phase, revealing distinct colored bands.
BioInteractive Photosynthetic Pigments and Light Absorption 1
Which wavelengths of light does chlorophyll a absorb most strongly?