Photosynthesis

AP Biology· difficulty 3/5

Engelmann illuminated a strand of algae with a spectrum and counted aerobic bacteria along its length.

Wavelength (nm) Rate of photosynthesis 400 700

The action spectrum (rate of photosynthesis) most closely resembles which absorption spectrum?

  • A

    Carotenoids alone

  • B

    The combined absorption of chlorophylls and accessory pigments

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  • C

    Water absorption

  • D

    Hemoglobin

Explanation

The action spectrum tracks the wavelengths that drive photosynthesis. It closely matches the combined absorption of chlorophyll a, b, and accessory pigments, supporting their role in light capture.

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