AP BIOLOGY

PHOTOSYNTHESIS

PHOTOSYNTHETIC PIGMENTS

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Chlorophyll a appears blue-green because
A
It absorbs blue-green light
B
It reflects blue-green light
Explanation: 

Detailed explanation-1: -Chlorophyll gives plants their green color because it does not absorb the green wavelengths of white light. That particular light wavelength is reflected from the plant, so it appears green. Plants that use photosynthesis to make their own food are called autotrophs.

Detailed explanation-2: -As shown in detail in the absorption spectra, chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. Green light is not absorbed but reflected, making the plant appear green.

Detailed explanation-3: -Blue (420-450nm) and Red (620-680nm): Chlorophyll a is the most abundant pigment in plants. Chlorophyll a absorbs light mostly 430nm (blue) and 662nm (red) wavelength light. It reflects green light so it appears green to us. Chlorophyll b molecule has a similar structure to that of chlorophyll a.

Detailed explanation-4: -In conclusion, plant leaves are green because green light is less efficiently absorbed by chlorophylls a and b than red or blue light, and therefore green light has a higher probability to become diffusely reflected from cell walls than red or blue light. Chlorophylls do not reflect light.

Detailed explanation-5: -The green color of the plant is due to the presence of chlorophyll as it does not absorb but reflects green color light. Chlorophyll absorbs light in the blue and red regions of the visible spectrum. Therefore, chlorophyll appears green because it reflects green light. So, option A is the correct option.

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