I like your question. I thought the other
colors appeared when the chlorophyll disappeared -
that the other colors were there in the green
leaves, but the green chlorophyll hid them.
It turns out I'm right, but only for the
yellow [xanthophylls] and
orange [beta carotene] pigments. The red
and purple[!] pigments are first synthesized
by the leaves in the late summer, when the
chlorophylls disappear. The chlorophylls
degrade into colorless molecules called
tetrapyrroles. Wikipedia has a nice article
about this -
Autumn leaf color
When we eat beta-carotene (in orange food, like
carrots), some of it is converted to Vitamin A in
our bodies. Vitamin A is an important molecule
for vision, in the retinas of our eyes.
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