Photosynthetic pigments types, what wavelengths they absorb, where they transfer energy.

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Multiple Choice

Photosynthetic pigments types, what wavelengths they absorb, where they transfer energy.

The key idea is that photosynthetic pigments capture light and funnel that energy to the reaction center where charge separation begins. Chlorophyll a is the main pigment in the reaction center, and it works with accessory pigments like chlorophyll b to broaden the light that can be used. Chlorophyll a absorbs strongly in the red and blue parts of the spectrum, and energy absorbed by chlorophyll b and other antenna pigments is transferred to the reaction center chlorophyll a. There, the excited chlorophyll a donates an electron, becoming oxidized and starting the initial steps of photosynthesis. This makes the statement about chlorophylls A and B correct: they cover red and blue wavelengths, and the energy is transferred to the reaction center chlorophyll that drives the photochemical reaction. Other options miss in important ways. Carotenoids do help harvest light and transfer energy to the photosystems, but their typical absorption is blue to green rather than yellow, so labeling their absorbed wavelength as yellow isn’t accurate. Chlorophylls C and D occur in some algae and not the main pigments of most plants, and they don’t primarily absorb green light in a way that supports the standard energy transfer described. Phycobilins do absorb in the orange to red region (not infrared) and they transfer energy to the photosystems as well, but the specific combination of pigments and wavelengths described in the other choices isn’t right for the common mechanism found in many photosynthetic systems.

The key idea is that photosynthetic pigments capture light and funnel that energy to the reaction center where charge separation begins. Chlorophyll a is the main pigment in the reaction center, and it works with accessory pigments like chlorophyll b to broaden the light that can be used. Chlorophyll a absorbs strongly in the red and blue parts of the spectrum, and energy absorbed by chlorophyll b and other antenna pigments is transferred to the reaction center chlorophyll a. There, the excited chlorophyll a donates an electron, becoming oxidized and starting the initial steps of photosynthesis.

This makes the statement about chlorophylls A and B correct: they cover red and blue wavelengths, and the energy is transferred to the reaction center chlorophyll that drives the photochemical reaction.

Other options miss in important ways. Carotenoids do help harvest light and transfer energy to the photosystems, but their typical absorption is blue to green rather than yellow, so labeling their absorbed wavelength as yellow isn’t accurate. Chlorophylls C and D occur in some algae and not the main pigments of most plants, and they don’t primarily absorb green light in a way that supports the standard energy transfer described. Phycobilins do absorb in the orange to red region (not infrared) and they transfer energy to the photosystems as well, but the specific combination of pigments and wavelengths described in the other choices isn’t right for the common mechanism found in many photosynthetic systems.

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