Vitamin C Flashcards
How many hydrogen is AA able to donate
2OH
What are the two steps to get to DHAA
- Ascorbyl radical (loss H +e-)
- DHAA (loss H +e-)
What is the precursor to AA
D-glucose
Bays, birds, fish and humans lack which enzyme to make AA
Gulonolactone oxidase
2 transporters of AA
SCVT1 - low affinity high capacity, whole body homeostats
SCVT2 - high affinity, low capacity, metabolically active and specialized tissue
What is the bioavailable difference of AA and DHAA
AA - 80-90% bioavailable up to 100mg dose
DHAA - 10% bioavailable
How does DHAA get transported around the body
facilitative transport
GLUT - 1,3,4
What is the total body pool size of AA
1500mg
Half life of AA
20 days
Where would you find SVCT1
Dietary absorption, renal reabsorption
intestine, kidney transporter, reproductive organs, skin, lung, liver, pancreases
Where would you find SVCT2
Brain, adrenal glands, leukocytes, platelets
if AA is oxidized to DHAA how does it get back
Reduced back by GSH and NADPH (NADPH to recycle GSSG back to GSH)
What forms of AA are excreted into the urine.
Dehydroaxcocorbate, diketogluconate, oxalic acid and excess ascorbate
What % of Vit C is excreted as oxalic acid
25%
Plasma levels above ___ exceeds renal threshold and vit c will not be reabsorbed
1.4mg/dL
What body pool total leads to metabolites in urine and which leads to ascorbate acid in the urine
<1500 mg leads to only breakdown metabolites
>1500mg leads to proportionally more ascorbate
What are the enzymatic and the non-enzymatic functions of Vit C
Enzymatic: monooxygenases, dioxygenase
Non-enzymatic: antioxidant, iron absorption, tetrahydrobiopterin recycling
What is required in the conversion of dopamine to norepinephrine (monooxygenase)
Vit C and Copper
hydroxylation of proline and lysin stimulates?
proper folding to structural stability
Collagen hydroxylation requires
proline or lysin,
Fe3 to Fe2
AA
GSH
NADPH
What is the role of tocopherol
Lipid membrane
protects against lipid membrane stress
Has a benzene ring of double bonds which allows it to accept free radicals
Can Vit C become a radical?
Yes, but it is less harmful than other forms
At what increase rate does Vit C enhance Fe absorption
10-fold
Why do people with Vit C deficiency have low energy?
Iron absorption
Epinephrin production
RDA for Vit C
Females: 75mg — 85(P) — 120 (L)
Males: 90mg
UL for Vit C
2000mg
What provides stability to or destruction of vit C
Stability: acidic
Destroyed: heat, light, oxidation, alkaline
What are some symptoms to AA deficiency
Anemia - fatigue (NE, Iron)\
Atherosclerotic-type plaques (recycle BH4, NO)
Collagen syn =
Dermal hemorrhages, bone fragility, wound healing, infection, bleeding gums, loose teeth
What are the 4 H’s of scurvy
Hemorrhagic
Hyperkeratosis of hair follicles
Hypochondriasis (psy)
Hematological (iron)
How much mg prevents scurvy?
10mg
If the body can tolerate 1g of AA why does AA toxicity happen?
repeated doses
Why would AA toxicity lead to kidney stones?
must AA is broken down into oxalic acid with calcium in the kidneys leads to kidney stones
