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- n. A chlorophyll from which the central magnesium atom has been removed
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In even slightly acidic water, the plentiful hydrogen ions displace the magnesium, a change that turns chlorophyll a into grayish-green pheophytin a, chlorophyll b into yellowish pheophytin b.
The structure shows the precise arrangement in the L and M subunits of the photochemically active groups – two chlorophyll molecules forming a dimer, two monomeric chlorophylls, two pheophytin molecules (these lack the central magnesium ion of chlorophyll), one quinone molecule, called
When the vegetables are heated for longer periods of time or exposed to acid, the magnesium is removed from the center of the molecule and replaced with an atom of hydrogen, which in turn changes the chlorophyll a and chlorophyll b into pheophytin a and pheophytin b.
Details in the protein environment around chlorophyll and pheophytin explain why only the right half (the
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