NTD412 - Antioxidants - Vitamin C

28 terms by gotjoosy

Create a new folder

Advertisement Upgrade to remove ads

another name for vitamin c

ascorbic acid

structure

C6H8O6, the only essential carbohydrate

sources: endogenous?

humans lack the enzyme (gulonolactone oxidase) to synthesize it but some animals can

best food sources

green veggies (asparagus, broccoli, brussels sprouts, etc.), citrus fruits (oj, grapefruit, cantaloupe), strawberries, potatoes

what can destroy vitamin c in foods?

heat, oxygen, high pH

digestion

no steps are required

absorption (location, mechanism)

small intestine, sodium dependent active transport (passive diffusion in stomach + small intestine at high intakes; dehydroascorbate via facilitated diffusion)

absorption: inhibitors

high intracellular glucose, high concurrent intakes of iron

transport

into plasma in free form (ascorbate anion); cellular uptake requires sodium and a carrier and sometimes energy

storage

highest concentrations in adrenal & pituitary glands (also: liver, spleen, heart, kidneys, lungs, pancreas, leukocytes)

two main functions

antioxidant, collagen synthesis

other functions

carnitine synthesis; tyrosine synthesis & catabolism, neurotransmitter synthesis, microsomal metabolism

functions: collagen synthesis

after collagen chains are made, vitamin C helps cross-link it into its helix configuration via the hydroxylation of proline and lysine

functions: antioxidant activity

related to its general capacity as a reducing agent/electron donor in aqueous solutions: (1) regenerates other antioxidants (2) reduces free radicals before they can damage cells, becomes oxidized in the process + must be regenerated

free radicals

molecules with 1 unpaired electron that attakcs nucleic acids in DNA, PUFA in phospholipids, and proteins in cells; can be cancerous (DNA)

functions: cold prevention?

mostly refuted, may weakly help

functions: cancer prevention?

possibly of GI tract (oral cavity, pharynx, esophagus, stomach); possible mechanisms: immunocompetence, antioxidant, ability to detoxify carcinogens/block carcinogenic processes

functions: cardiovascular disease prevention?

low vitamin C status may increase blood total cholesterol; high status may decrease blood pressure and increase HDL

functions: cataracts prevention?

cataracts result partly from oxidative damage to proteins in the eye's lens, so it works as an antioxidant

interactions with other nutrients

enhances nonheme intestinal absorption by reducing ferrous to ferric; decreases serum copper and ceruloplasmin but may inhibit binding to metallothionein

excretion

intact or oxidized to dehydroascorbate in the liver or kidneys; mostly excreted in urine; renal absorption threshold = 1.2mg/dL

when does the RDA increase?

pregnancy, lactation, smoking status

deficiency results in _____ when ____

scurvy, total body vitamin C pools < 300mg and plasma vitamin C concentrations <.2mg/dL

signs & symptoms of deficiency

tend to result from impaired hydroxyproline and hydroxylysine synthesis for collagen: bleeding gums, hemorrhages, easy bruising, impaired wound + fracture healing, joint pain, loose/decaying teeth, hyperkeratosis of hair follicles

deficiency: populations at risk

elderly, alcoholics, drug abusers, people on poor diets (esp. infants from poor SES), people with diabetes and some cancers

toxicity side effects

abdominal pain/nausea/vomiting, osmotic diarrhea, increased risk of kidney stones due to metabolism into oxalate, iron toxicity

assessment of nutriture

plasma and serum concentrations respond to changes in dietary vitamin C intakes so it's a good measure of recent intake

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set