Vitamin C (Ascorbic Acid) Flashcards
(30 cards)
What are human unable to do (regarding vitamin C) ?
to synthesize vitamin C derived from glucose due to the lack of gulonolactone oxidase
what is gulonolactone oxidase?
the last enzyme in the vitamin C synthetic pathway
how is vitamin C found in foods?
mostly as ascorbic acid
how is vitamin C destroyed?
by heat, light, oxidation, and alkaline solutions
when is vitamin C stable?
in acidic solutions
when is vitamin C oxidatively damaged?
in the presence of oxygen and minerals such as iron and copper
does vitamin C require digestion prior to being absorbed into the intestinal cells?
no
what does the absorption of vitamin C look like?
crosses the intestinal cell brush border membrane occurs through the small intestine especially proximal jejunum and requires sodium-dependent vitamin c transporters
when is absorption down-regulated?
when the vitamin is present in large amounts - limiting the vitamin’s absorption when superphysiological doses are ingested
how is dehydroascrobic acid absorbed?
oxidized in the GI tract and absorbed by FD via GLUT - mainly GLUT 1 and 3
where is dehydroascorbic acid found?
in foods or formed through ascorbic acid
how does vitamin C enter the blood plasma?
diffuses out of intestinal cells into the extracellular fluid through volume-sensitive anion channels
what are other ways that vitamin C may exist the intestinal cells?
via calcium-dependent channels or exocytosis
where is a majority of vitamin C found in the blood?
- 70% found in the plasma and red blood cells
- 30% is found in the white blood cells
where are high concentration of vitamin C found?
adrenal, pituitary glands, eye, brain, white blood cells and neurons
what facilities ascorbic acid uptake into body cells?
SVCT1 (high capacity/low affinity)
SVCT2 (low capacity/high affinity)
where is SVCT1 primarily found?
in the intestine, liver and kidneys
where is SVCT2 primarily found?
present in most metabolically active tissues - brain, neurons, bine and endocrine glands
what is the function of vitamin C?
reducing agent (electron donor) - to keep iron and copper atoms in the reduced state
what is vitamin C necessary for?
the production of collagen
what is another function of vitamin C?
it’s needed for the formation and maintenance of the basement membrane lining the capillaries (holding together endothelial cells and scar tissue)
what is the function of carnitine?
essential for the transport of long-chain fatty acids from the cell cytosol into the mitochondria for B-oxidation (and thus energy production)
what are the sources of tyrosine?
ingested from foods or generated in the body from phenylalanine oxidation
why is the interaction between vitamin C and mineral iron imporatnt?
enhances the intestinal absorption of nonheme iron most likely by reducing iron ferri (3+) state to a ferrous (2+)
