Vitamin C

Question 1

Does vit C require digestion for absorption

Answer 1

No

Question 2

Where is vit c absorbed

Answer 2

Small intestine

Question 3

Two pathways by which vit C absorbed

Answer 3

SVCT1

GLUT1 and GLUT3

Question 4

SVCT1 mainly absorbs what form of vitamin c

Answer 4

ascorbate

Question 5

What down regulates SVCT1

Answer 5

High amounts of vitamin C

Question 6

How is dehydroascorbate absorbed

Answer 6

Can compete with glucose for absorption via GLUT1 and GLUT3

Question 7

Most oxidized form of vitamin c

Answer 7

Dehydroascorbate

Question 8

Ascorbate from

Answer 8

Less oxidized form

Question 9

What happens to dehydroascorbate after absorption

Answer 9

Reduced back to ascorbic acid

Question 10

What reduces dehydroascorbate to ascorbic acid

And what two things are generated

Answer 10

Glutathione (GSH)

Ascorbic acid and GSSG (oxidized glutathione)

Question 11

What are 3 reducing agents for vitamin c

Answer 11

Glutathione

NADPH

Glutaredoxin

Question 12

5 functions of vit C

Answer 12

• Collagen synthesis
• Carnitine synthesis
• Tyrosine synthesis and catabolism
• Neurotransmitter synthesis
• Oxidation/Reduction Agent

Question 13

the cofactor being reduced by vitamin C in collagen synthesis

Answer 13

Ferric iron (Fe3+)

Question 14

5 Things collagen is important for

Answer 14

skin, bones, tendons, intracellular cement and cartilage

Question 15

Three hydroxylation reactions, using Vitamin C, enables what in relation to collagen

Answer 15

the collagen molecule to cross-link into the triple helix conformation

Question 16

Collagen hydroxylations are carried out by metalloenzymes which require what?

Answer 16

reduced iron (ferrous, Fe2+) regeneration for subsequent oxidation (ferric, Fe3+)

Question 17

How does vit c provide antioxidant activity

Answer 17

provides electrons/hydrogen and becomes oxidized

Question 18

Regeneration of ascorbic acid/ascorbate is accomplished in what 6 different ways

Answer 18

–Two ascorbyl radicals react to form ascorbic acid and dehydroascorbic acid
–Enzymes (reductases) can reduce ascorbyl radicals
–Niacin (NADPH)
–Dihydrolipoic acid
–Glutathione
–Thioredoxin

Question 19

How does vit c improve absorption of iron

Answer 19

•Reduces to ferrous state for absorption of nonheme iron

Forms soluble complex to improve absorption

Question 20

What is scurvy

Answer 20

Vit c deficiency

Impaired collagen synthesis

Question 21

Four Hs of scurvy

Answer 21

•Hemorrhagic signs, Hyperkeratosis, Hypochondriasis, Hematological abnormalities (impaired Fe abs)

Question 22

Enzyme needed in order to synthesize vitamin C

Answer 22

Gulonolactone oxidase

Question 23

Cofactor being reduced in carnitine synthesis

Answer 23

Iron (Fe3+)

Question 24

What is the cofactors reduced by vit c for tyrosine

Answer 24

Copper and iron

Question 25

What is the cofactor(s) reduced by vit c for neurotransmitter synthesis

Answer 25

Copper (Cu2+)