Carotenoids extra

Question 1

where do carotenoids go in gut?

Answer 1

lumen of small intestine

Question 2

2 methods of carotenoid absorption into enterocyte

Answer 2

1. passive diffusion
2. SR-B1

Question 3

carotenoid passive diffusion

Answer 3

1. carotenoids packed into micelles in intestinal lumen
2. micelle diffuses into enterocyte

Question 4

which method of carotenoid absorption is the main method?

Answer 4

passive diffusion

Question 5

SR-B1 absorption

Answer 5

secondary, competitive, and saturable
carotenoids compete with other lipids that it absorbs (including cholesterol)

Question 6

if the body needs vit A, carotenoids undero __

Answer 6

if the body needs vit A, carotenoids undero cleavage

Question 7

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)

Answer 7

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)

Question 8

within enterocyte, 2 fates of carotenoids

Answer 8

1. packed into chylomicrons
2. undergo cleavage

Question 9

symmetrical cleavage is catalyzed by __ and produces __ molcules of retinal

Answer 9

symmetrical cleavage is catalyzed by BCO1 and produces 2 molcules of retinal

Question 10

asymmetrical cleavage is catalyzed by __ and produces __ molecules of retinal and one molecule of __

Answer 10

asymmetrical cleavage is catalyzed by BCO2 and produces one molecules of retinal and one molecule of beta-apocarotenal

Question 11

fate of carotenoids in chylomicrons

Answer 11

1. chylomicrons w/ carotenoids pushed into portal circulation
2. transported through body and metabolized in muscle and adipose by LPL
3. carotenoids in chylomicron remnants go to liver

Question 12

where do carotenoids in chylomicron remnants go?

Answer 12

liver

Question 13

2 fates of carotenoids that reach liver

Answer 13

1. cleavage by BCO1 and BCO2
2. carotenoids packed into VLDL

Question 14

fate of carotenoids packed into VLDL

Answer 14

1. can become LDL in circulation
2. peripheral cells uptake LDL

Question 15

what situations produce an overabundance of free radicals

Answer 15

chemotherapy

Question 16

oxygen singlets can __ DNA, proteins and __ them

Answer 16

oxygen singlets can oxidize DNA, proteins and destroy them

Question 17

carotenoids can act as __ to __ oxygen singlets

Answer 17

carotenoids can act as antioxidants to quench oxygen singlets

Question 18

most potent anti-oxidant form

Answer 18

beta-carotenes

Question 19

beta-carotenes take a free radical’s __ and give it off in the form of __

Answer 19

beta-carotenes take a free radical’s energy and give it off in the form of heat

Question 20

which 2 molecules have antioxidant properties?

Answer 20

vit C and beta-carotenes

Question 21

what molecule has highest antioxidant capacity?

Answer 21

beta-carotenes bc vit C must be reduced and reused

Question 22

vit C exerts its antioxidant function in __, while carotenoids exert antioxidant function in the __, like vitamin __

Answer 22

vit C exerts its antioxidant function in cytosol, while carotenoids exert antioxidant function in the membrane, like vitamin E

Question 23

beta-carotene works synergistically with vit __ in scavenging radicals and inhibiting lipid peroxidation

Answer 23

beta-carotene works synergistically with vit E in scavenging radicals and inhibiting lipid peroxidation

Question 24

beta-carotene __ lipid peroxidation

Answer 24

beta-carotene inhibits lipid peroxidation

Question 25

what is lipid peroxidation?

Answer 25

when oxidants, like free radicals, attack lipids
BAD