BioInteractive Photosynthetic Pigments and Light Absorption 2 — Questions and Answers
Question 1: What is the difference between the absorption spectrum and the action spectrum of a pigment?
- Absorption spectrum shows light absorbed by the pigment; action spectrum shows which wavelengths drive photosynthesis (Correct answer)
- They are identical
- Action spectrum shows light reflected
- Absorption spectrum measures glucose output
Correct answer: Absorption spectrum shows light absorbed by the pigment; action spectrum shows which wavelengths drive photosynthesis
The absorption spectrum measures which wavelengths a pigment absorbs, while the action spectrum measures the rate of photosynthesis at each wavelength.
Question 2: Which pigment absorbs light primarily in the blue-violet range and is found in antenna complexes?
- Chlorophyll b (Correct answer)
- Chlorophyll a
- Beta-carotene
- Phycoerythrin
Correct answer: Chlorophyll b
Chlorophyll b absorbs light mainly in the blue-violet range (~453 nm) and transfers energy to chlorophyll a reaction centers.
Question 3: What is the light-harvesting complex (antenna complex) in a photosystem?
- A cluster of pigment molecules that absorbs light and funnels energy to the reaction center (Correct answer)
- The site where water is split
- The enzyme that fixes CO2
- The ATP synthase complex
Correct answer: A cluster of pigment molecules that absorbs light and funnels energy to the reaction center
The antenna complex consists of many chlorophyll and accessory pigment molecules that capture photons and transfer the energy via resonance to the reaction center.
Question 4: How does increasing light intensity affect the rate of photosynthesis up to a point?
- Rate increases until a light saturation point is reached (Correct answer)
- Rate decreases linearly
- Rate remains constant
- Rate immediately plateaus at any intensity
Correct answer: Rate increases until a light saturation point is reached
As light intensity increases, photosynthesis rates rise until the light saturation point, where other factors (CO2, temperature) become limiting.
Question 5: What is resonance energy transfer in the context of photosynthetic pigments?
- Energy passes from one pigment molecule to adjacent ones until it reaches the reaction center (Correct answer)
- Electrons physically move between pigments
- Photons are stored in pigment bonds
- ATP is transferred between antenna complexes
Correct answer: Energy passes from one pigment molecule to adjacent ones until it reaches the reaction center
Resonance energy transfer (also called Förster resonance) moves excitation energy between closely packed pigment molecules without electron transfer until the reaction center is reached.
Question 6: Why do plants contain multiple types of photosynthetic pigments?
- To capture a broader range of light wavelengths and increase photosynthetic efficiency (Correct answer)
- Because each pigment fixes a different type of CO2
- To produce different sugars
- To protect the plant from disease
Correct answer: To capture a broader range of light wavelengths and increase photosynthetic efficiency
Multiple pigments with different absorption spectra collectively capture more of the solar spectrum, maximizing the energy available for photosynthesis.
BioInteractive Photosynthetic Pigments and Light Absorption 2
What is the difference between the absorption spectrum and the action spectrum of a pigment?