10 vitamin C

Question 1

Other names for vitC

Answer 1

ascorbic acid

ascorbate

Question 2

Is vit C essential?

Answer 2

Yes

• there is a pathway but humans don’t have the enzymes
• primates, fruit bats, guinea pig, and some birds can produce it

Question 3

Reduced and oxidized forms of VitC

Answer 3

Reduced
Ascorbic acid / ascorbate

Oxidized
dehydroascorbate / dehydro ascorbic acid

• can exist in both forms

Question 4

What would explain why humans can’t produce Vitamin C anymore?

Answer 4

evolution

- high vit C in diet, no longer needed to produce it

Question 5

What is vit C synthesized from? Enzyme missing?

Answer 5

Glucose

- gulonolactone oxidase

Question 6

Types of reactions vit C is involved in?

Answer 6

Hydroxylase reactions
(reducing agent)
- donates hydrogens (becomes dehydroascorbic acid

Question 7

Metabolic roles of vit C

Answer 7

1. collagen formation*
2. carnitine synthesis
3. tyrosine metbolism
   - catabolism
   - synthesis of neurotransmitters
4. antioxidant

Question 8

Largest protein in the body?

Answer 8

Collagen

Question 9

How is collagen formed?

Answer 9

proline and lysine residues needs to be hydroxylated (cross linking needed to be strong)

• Proplyl / lysyl hydroxylase
• iron needed as cofactor
• vit C keeps iron in reduced state (Fe2+ ferrous acid)

Question 10

Role of carnitine

Answer 10

transports fatty acids into mitochondria

Question 11

How is carnitine synthesized?

Answer 11

from lysine and methionine

• two iron-dependent hydroxylase enzymes
• ascorbic acid keeps iron in reduced state

Question 12

Tyrosine metabolism?

Answer 12

tyrosine -> dopamine -> norepinephrine 
(neurotransmitters)
- dopamine-B-hydroxylase
- needs copper
- vit C keeps copper reduced state

Question 13

Antioxidant protection

Answer 13

Direct
- neutralizes free radicals and other oxidant species

Indirect

• supplies electrons to regenerate other antioxidants (by reducing them)
• vit E, glutathione, flavonoids

Question 14

Other micronutrients vit C acts on?

Answer 14

iron

copper

Question 15

Vit C interaction with iron

Answer 15

• enhances absorption of non-heme iron by:
  1. reduces ferric to ferrous
  2. forms soluble complex with iron
  3. facilitates incorporation into ferritin

Question 16

vit C interaction with copper

Answer 16

inhibits copper absorption

• wilsons disease
• excessive copper in tissue
• autosomal recessive disorder (1 in 100 people)

Question 17

What increase required vit C intake?

Answer 17

smokers

- extra 35mg per day

Question 18

toxicity of vit C?

Answer 18

Not very
- UL (2000mg) well above RDA (90mg)

1. Oxalate kidney stones
   - oxalate metabolite of vit C, combines with calcium
2. Iron metabolism
   - hemochromatosis - iron can’t be excreted

Question 19

Vit C food sources?

Answer 19

fruits and vegetables

organ meats

Question 20

What reduces food it C content?

Answer 20

highly susceptible to oxidation

- dramatically reduced during storage

Question 21

Vit C deficiency

Answer 21

scurvy
- 45-80 days after no vit C

symptoms
- fatigue**
- impaired wound healing
hemorrhage in skin, mucous membranes and muscles
-gums
- weakness of collagenous structures (bones, cartilage, teeth)
-depression
-edema

Question 22

Vit C health and diseases

Answer 22

1. common cold
   - decrease severity
   - reduced inflamation
2. Cataracts
   - vit C concentrated in eye
3. Cancer
4. Cardiovascular Disease
   - neutralize oxidized LDLs