Which pigment in chloroplasts is primarily responsible for absorbing light during photosynthesis?

• A. Carotenoids
• B. Melanin
• C. Chlorophyll
• D. Hemoglobin

Answer: (C)

Chlorophyll is the pigment in chloroplasts that does the primary light catching for photosynthesis. It sits in the thylakoid membranes of the photosystems and absorbs mostly blue and red light, using that energy to excite electrons and drive the light reactions that produce ATP and NADPH. Because it absorbs those wavelengths, leaves appear green since chlorophyll reflects green light. Other pigments, like carotenoids, also absorb light and help broaden the range of usable light and protect against excess energy, but they’re secondary to chlorophyll in capturing light for driving the main photosynthetic reactions. Pigments such as melanin and hemoglobin aren’t involved in chloroplast photosynthesis.