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Metabolism Exam 4 > Vitamin C > Flashcards

Vitamin C Flashcards

1
Q

What is the active form of Vitamin C

A

Ascorbic acid

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2
Q

What reaction does ascorbic acid undergo

A

oxidation (electron donor)

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3
Q

What is formed after oxidation of ascorbic acid

A

Ascorbyl radical (free radical)

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4
Q

What reaction does ascorbyl radical undergo

A

oxidation (electron donor)

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5
Q

What is formed after oxidation of ascorbyl radical

A

dehydroascorbic acid (stable, inactive)

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6
Q

What reaction does dehydroascorbic acid undergo

A

Reduction

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7
Q

What is formed after reduction of dehydroascorbic acid

A

Ascorbic acid

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8
Q

What enzyme system reduces dehydroascorbic acid

A

Glucathione perioxidase

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9
Q

What is a structural element of the glucathione perioxidase system

A

Selenium

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10
Q

How is vitamin C digested

A

No digestion!

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11
Q

What are non-citrus sources of vitamin C

A

cantaloupe, kiwi, mango, watermelon, broccoli, peppers, brussel sprouts

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12
Q

What is the RDA for vitamin C

A

75mg/day women; 90mg/day men

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13
Q

How is vitamin C absorbed

A

Saturable transporter; diffusion at high concentration

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14
Q

What is the absorption % of vitamin C

A

75-90%; at high rates of consumption, absorption decreases

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15
Q

How is vitamin C transported in blood

A

free form (water-soluble/no transporter)

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16
Q

Does absorption of vitamin C into cells require a transporter

A

Yes

17
Q

At what amount will blood level saturate

A

150-200mg

18
Q

What happens to vitamin C once blood level saturation occurs

A

Excreted in urine

19
Q

What is the vitamin C saturation point for WBCs

A

100mg

20
Q

What is a potential function for a high dose of vitamin C

A

pro-oxidant, isolate to kill cancer cells

21
Q

Vitamin C is an electron donor for what

A

8 mammalian enzymes

22
Q

What is the function of monooxygenase

A

Insert Oxygen

23
Q

In what processes are monooxygenases involved

A

Neurotransmitter synthesis(1 enzyme), peptide hormones and post-translational modification(1)

24
Q

What neurotransmitters are synthesized using monooxygenase

A

Serotonin, norepinephrine, hormones

25
Q

What is the function of diooxygenase

A

Insert O2

26
Q

In what processes are dioxygenases involved

A

Collagen synthesis (3enzymes), carnitine synthesis(2), tyrosine synthesis and catabolism (1)

27
Q

What is the function of carnitine

A

Fatty acid transport

28
Q

In what step in collagen synthesis is vitamin C involved

A

Cofactor for dioxygenase enzyme required for hydroxylation during post-translational modification of pro-collagen chain

29
Q

What happens to vitamin C during collagen synthesis

A

Becomes oxidized

30
Q

What is the most effective reducing agent for dioxygenase

A

Vitamin C

31
Q

How does vitamin C interact with vitamin E

A

Regeneration; donates an electron to reduce back to active form

Metabolism Exam 4 (5 decks)

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