Carotenoid
<p>Jul 22, 2011 09:52 AM
 
carotenoids  tetraterpanoid pigments... from  chloroplasts and chromoplasts of plants
and algae
 
Carotenoids are not manufac in the animal kingdom.
 
600 known carotenoids:  TWO CLASSES
 
xanthophylls contain oxygen and
carotenes ... pure hydrocarbons  ... no oxgen.
 
There are over 600 known carotenoids; they are split into two classes,
<b> </b><a title="Xanthophyll" href="/wiki/Xanthophyll"><b>xanthophylls</b></a><b> (which contain oxygen) and</b>
 
<b> </b><a title="Carotene" href="/wiki/Carotene"><b>carotenes</b></a><b> (which are purely hydrocarbons, and contain no oxygen</b>).
 
 
 Carotenoids in general absorb blue light. They serve two key roles in plants and algae: 
they absorb light energy for use in photosynthesis, and they protect chlorophyll from photodamage.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1">[2]</a></sup> 
 
In humans, four carotenoids (<a class="mw-redirect" title="Beta-carotene" href="/wiki/Beta-carotene">beta-carotene</a>, <a class="mw-redirect" title="Alpha-carotene" href="/wiki/Alpha-carotene">alpha-carotene</a>, <a class="mw-redirect" title="Gamma-carotene" href="/wiki/Gamma-carotene">gamma-carotene</a>, and beta-<a title="Cryptoxanthin" href="/wiki/Cryptoxanthin">cryptoxanthin</a>) have <a title="Vitamin A" href="/wiki/Vitamin_A">vitamin A</a> activity (meaning they can be converted to <a title="Retinal" href="/wiki/Retinal">retinal</a>), and these and other carotenoids can also act as <a title="Antioxidant" href="/wiki/Antioxidant">antioxidants</a>.
 
 In the eye, certain other carotenoids (<a title="Lutein" href="/wiki/Lutein">lutein</a> and <a title="Zeaxanthin" href="/wiki/Zeaxanthin">zeaxanthin</a>) apparently act directly to absorb damaging blue and near-ultraviolet light, in order to protect the <a class="mw-redirect" title="Macula lutea" href="/wiki/Macula_lutea">macula lutea</a>.</p>