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dnwltla dnwltla
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6 years ago
Explain how the structure of the chlorophyll molecules and the carotenoids facilitate energy absorption.
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6 years ago
- A pigment’s color is the result of photons of light that it DOES NOT absorb; instead of being absorbed, these photons are reflected off the pigment or transmitted through the pigment to reach your eyes  Following light absorption, the potential energy of excited electrons within chlorophyll isused in photosynthetic electron transport to synthesize the energy-rich compounds NADPH and ATP- These molecules in turn consumed in the Calvin cycle of photosynthesis to convert carbon dioxide into carbohydrates  Energy from the Sun enters the biosphere through photosynthesis  While photosynthesis converts carbon dioxide into carbohydrates, it is the process of cellular respiration that breaks down carbohydrates and other molecules, trapping the released energy as A

Pigments have an alternating arrangement of single and double bonds in the molecule; these are conjugated bonds that share electrons in pi orbitals across the whole structure. Electrons move readily along a conjugated bond series like they do in copper wire.

When a photon of just the right wavelength strikes an electron resonating in the pigment, the electron can absorb the photon and get promoted to a higher quantum level. The photon must have just the exact amount of energy to boost the electron from its current level to its new level or it cannot be absorbed.

Conjugated Bond length determines wavelength to be absorbed - The specific wavelength of light that can be absorbed is determined by the number and structure of conjugated bonds in the pigment molecule.

Chlorophyll's conjugated bonds are found in:
1 - the porphyrin ring, made up of a cyclic tertapyrrole that chelates magnesium
2 - in the side chain, which forms a long hydrocarbon tail to the heme ring.


Carotenoid pigments are linear (lycopene) or rings (beta carotene) based on conjugated 40 carbon precursor hydrocarbon molecules. Chlorophyll A (C55H72MgN4O5) is more polar and much larger than nonpolar carotene so has a very different shape and conjugated bond system.
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