Carotenoids extra Flashcards
where do carotenoids go in gut?
lumen of small intestine
2 methods of carotenoid absorption into enterocyte
- passive diffusion
- SR-B1
carotenoid passive diffusion
- carotenoids packed into micelles in intestinal lumen
- micelle diffuses into enterocyte
which method of carotenoid absorption is the main method?
passive diffusion
SR-B1 absorption
secondary, competitive, and saturable
carotenoids compete with other lipids that it absorbs (including cholesterol)
if the body needs vit A, carotenoids undero __
if the body needs vit A, carotenoids undero cleavage
if there is excess vit A, carotenoids are __ to other parts of the body where they are used as __ (the primary bio function of carotenoids)
if there is excess vit A, carotenoids are transported to other parts of the body where they are used as membrane antioxidants (the primary bio function of carotenoids)
within enterocyte, 2 fates of carotenoids
- packed into chylomicrons
- undergo cleavage
symmetrical cleavage is catalyzed by __ and produces __ molcules of retinal
symmetrical cleavage is catalyzed by BCO1 and produces 2 molcules of retinal
asymmetrical cleavage is catalyzed by __ and produces __ molecules of retinal and one molecule of __
asymmetrical cleavage is catalyzed by BCO2 and produces one molecules of retinal and one molecule of beta-apocarotenal
fate of carotenoids in chylomicrons
- chylomicrons w/ carotenoids pushed into portal circulation
- transported through body and metabolized in muscle and adipose by LPL
- carotenoids in chylomicron remnants go to liver
where do carotenoids in chylomicron remnants go?
liver
2 fates of carotenoids that reach liver
- cleavage by BCO1 and BCO2
- carotenoids packed into VLDL
fate of carotenoids packed into VLDL
- can become LDL in circulation
- peripheral cells uptake LDL
what situations produce an overabundance of free radicals
chemotherapy
oxygen singlets can __ DNA, proteins and __ them
oxygen singlets can oxidize DNA, proteins and destroy them
carotenoids can act as __ to __ oxygen singlets
carotenoids can act as antioxidants to quench oxygen singlets
most potent anti-oxidant form
beta-carotenes
beta-carotenes take a free radical’s __ and give it off in the form of __
beta-carotenes take a free radical’s energy and give it off in the form of heat
which 2 molecules have antioxidant properties?
vit C and beta-carotenes
what molecule has highest antioxidant capacity?
beta-carotenes bc vit C must be reduced and reused
vit C exerts its antioxidant function in __, while carotenoids exert antioxidant function in the __, like vitamin __
vit C exerts its antioxidant function in cytosol, while carotenoids exert antioxidant function in the membrane, like vitamin E
beta-carotene works synergistically with vit __ in scavenging radicals and inhibiting lipid peroxidation
beta-carotene works synergistically with vit E in scavenging radicals and inhibiting lipid peroxidation
beta-carotene __ lipid peroxidation
beta-carotene inhibits lipid peroxidation
what is lipid peroxidation?
when oxidants, like free radicals, attack lipids
BAD