Water-soluble vitamins Flashcards
Ascorbic acid conversion to diketogulonic acid is ________.
irreversible.
Can humans make vitamin C?
No way man
Name five things vitamin C is a cofactor for.
- Collagen synthesis
- Carnitine synthesis
- Norepinephrine synthesis
- Peptide hormone synthesis
- Tyrosine metabolism
Scurvy is primarily caused by a ____ ____ deficiency.
Vitamin C
Can vitamin C be toxic?
Yeah, over 2g/day causes diarrhea, bloating, enhanced ion absorption, hyperoxaluria.
Decubitus ulcers can be treated with ______.
Vitamin C
Which vitamin can enhance non-heme iron absorption?
Vitamin C
Which form of thiamine is most commonly used as a cofactor for bio reactions?
Diphosphate.
Name some sources of thiamine.
Whole grains, enriched grains, cereals, some veggies, legumes, meat, fish, poultry, dairy.
Thiamine is also known as vitamin ___.
B1
What do thiaminases and antithiamines do?
Degrade or inactivate thiamine!
Where in the GI tract are the active transporters located that transport B1? Which ones can be defective (genetic underlying cause)?
Jejunum and ileum. SLC19 transporters can be defective.
How long does it take to build up a body pool of thiamine?
30 days
Where is thiamine stored?
50% of the pool is in muscle. Some in liver
Can thiamine be toxic?
Nope.
Name four bioreactions in which thiamine is a cofactor.
- PP shunt (transketolases)
- alpha-KG DH
- Pyruvate DH
- alpha oxidation of branched FAs
How does thiamine deficiency result in reduced ATP and GTP synthesis?
No PP shunt –> no ribose sugar synthesis –> no purine synthesis
What causes Beri Beri?
Thiamine deficiency
Compare/contrast Dry and Wet Beri Beri.
Dry - peripheral neuropathy and calf tenderness.
Wet - tachycardia, low peripheral resistance, edema, heart failure, peripheral neuropathy.
Main difference is that Wet includes heart failure.
Which vitamin is involved in the synthesis of glutamine, GABA, and acetylcholine?
Thiamine
Deficiency of which vitamin causes Wernicke-Korsakoff syndrome?
Thiamine.
Name the symptoms of early Wernicke encephalopathy.
Opthalmoplegia, ataxia, confusion, atrophy and ventricular dilation, cerebellum neuronal loss
Name the symptoms of late Korsakoff’s psychosis.
Amnesia, confabulation, loss of spontaneity and initiative.
Niacin is also known as vitamin ___.
B3
Is niacin toxic?
Yeah 35 mg/day is TUL. Toxicity symptoms include heartburn, nausea, hepatotoxicity, hyperuricemia, gout, decreased insulin sensitivity, decreased glucose tolerance, and vasodilatory flushing.
Name six biological roles of niacin.
- Glycolysis
- Synthesis of FAs and cholesterol
- Synthesis of steroid hormones
- Synthesis of glutamate
- Synthesis of ribonucleotides
- Post-translational modification of proteins
Niacin can be made from which AA?
Tryptophan
Can Hartnup’s diasease cause niacin deficiency?
Yeah
What causes pellagra?
Niacin deficiency
What are the symptoms of pellagra?
Dermatitis, dementia, diarrhea, death
Is folate widely distributed in foods?
Yeah
Name two biological reactions in which B12 is used as a cofactor.
- Methionine synthase reaction (B12 - methyl)
2. Methyl Malonyl CoA Mutase reaction (B12 - adenosyl)
What was the primary reason for mandatory folic acid fortification?
To decrease incidence of neural tube defects.
Which has higher bioavailability: synthetic folic acid or folate naturally found in foods?
Synthetic folic acid (bioavailability is 85% vs 60% from food)
Where in the GI tract does folate absorption occur?
Small intestine
Where is folate stored? For how long can folate storage be adequate to sustain biochemical functions?
Stored in liver, can be adequate for 2-3 months.
Folate is also known as vitamin ___.
B9
How does B12 deficiency result in a folate deficiency?
Cannot regenerate THF from N5-methyl THF with methionine synthase reaction, so folate gets “trapped.”
Aside from methylation reactions, what is folate used for?
N10-methyl THF is used in purine synthesis
What is the relationship between folate intake and breast cancer risk?
Too little = higher risk, too much = higher risk
Name four risk factors for folate deficiency.
- Poor diet
- Alcoholism - it interferes with folate metabolism
- Malabsorption
- Medications
Defieincy of which vitamins can cause megaloblastic anemia?
Folate (B9) or B12 deficiency.
Chronically high homocysteine levels are associated with ______.
cardiac disease
What are the dietary sources of vitamin B12?
- Animal products
- Fortified food
- Yeast, fermented food
Describe the steps in B12 absorption.
- B12 is liberated from protein in the stomach.
- R factor binds to B12.
- Chyme goes into duodeum, and intrinsic factor binds to B12, replacing R factor.
- IF-B12 is absorbed in the ileum.
What is pernicious anemia and what does it put one at risk for?
It is loss of intrinsic factor - puts a person at risk of B12 deficiency.
What populations are at risk for B12 deficiency?
Vegetarians, older adults, people with malabsorptive diseases like Celiac, people that have had GI surgery, people with pernicious anemia.
Name four tests to assess for B12 deficiency.
- CBC
- Serum B12
- Methylmalonic acid
- Homocysteine
What three diseases may result from B12 deficiency?
- Megaloblastic anemia
- Neurologic problems including: combined systems degeneration, peripheral neuropathy, optic neuropathy.
- Neuropsychiatric: personality changes, memory impairment, depression.
How much more ascorbic acid do smokers need per day? Why?
Need 35mg/day more because smoking oxidizes vitamin C.
Scurvy can be prevented by as little as ___ mg/day of vitamin C.
10
What does “the three M’s” apply to?
Risk for niacin deficiency. Stands for maize, meat, molasses.
In what ways does alcohol mess with thiamin?
Alcohol inhibits thiamin transport out of the intestinal epithelial cell into the blood and also inhibits its phosphorylation into the active diphosphate form.
Does alcohol affect folate metabolism?
Yeah.
Megaloblastic anemia is a result of either _____ or ______ deficiency.
Folic acid/folate or B12 deficiency.
