Biochemistry First Aid- Nutrition (91-97) Flashcards
which vitamins are fat soluble
A, D, E, K
why do fat soluble vitamins have a higher risk of toxicity than water soluble
they accumulate in fat in the body tissues
what kinds of conditions can lead to deficiencies of fat soluble vitamins
malabsorption due to steatorrhea (e.g. caused by CF or sprue), mineral oil intake
list the water soluble vitamins (and their names)
B1=thiamine, B2=riboflavin, B3=niacin, B5=pantothenic acid, B6=pyridoxine, B7=biotin, B9= folate, B12= cobalamin
C= ascorbic acid
which water soluble vitamins don’t easily wash out of the body
cobalamin (B12) and folate (B9), which are stored in the liver
what illnesses commonly result from B complex (multiple B vitamin) deficiencies
dermatitis, glossitis, diarrhea
what is vitamin A called and what does it do
retinol:
antioxidant, visual pigments (retinal), important for specialization of epithelial cells, prevents squamous metaplasia
vitamin A is used to treat what conditions
measles and AML subtype M3
what does vitamin A deficiency cause
night blindness (nyctalopia), dry scaly skin (xerosis cutis), alopecia, corneal degeneration (keratomalacia), immune suppression
what is caused by excess vitamin A
arthralgias, skin changes (scaliness), alopecia, cerebral edema, pseudotumor cerebri (idiopathic intracranial hypertension), osteoporosis, hepatic abnormalities, teratogenic (cleft palate, cardiac abnormalities)
what must you do before prescribing a female isotretinoin for severe acne
pregnancy test must be negative
what are natural sources of vitamin A
liver and leafy veggies
thiamine pyrophosphate (TPP) is a cofactor for what enzymes
pyruvate dehydrogenase, alpha ketoglutarate dehydrogenase, transketolase, branched-chain ketoacid dehydrogenase
mnemonic for the first 3: ATP (alpha ketoglutarate dehydrogenase, transketolase, pyruvate dehydrogenase)
what major process is impaired in vitamin B1 deficiency
glucose breakdown
which tissues are affected first in vitamin B1 deficiency
highly aerobic tissues first: brain and heart
what two conditions are caused by thiamine deficiency
Wernicke-Korsakoff and beriberi
how is thiamine deficiency diagnosed
increased RBC transketolase activity after vitamin B1 administration
what parts of the brain are damaged in Wernicke-Korsakoff syndrome
medial dorsal nucleus of thalamus and mammillary bodies
what are the symptoms of dry beriberi vs. wet beriberi
dry: polyneuritis, symmetrical muscle wasting
wet: dilated cardiomyopathy, edema
what is the function of vitamin B2 (riboflavin)
vit B2 serves as a component of FAD and FMN (cofactors for redox reactions
what results from riboflavin deficiency
cheilosis (inflammation of lips and scaling at corners of mouth), corneal vascularization
what is the function of vitamin B3 (niacin)
component of NAD+ and NADP+, which are used in redox reactions
what amino acid is niacin derived from
tryptophan
niacin synthesis requires what other 2 vitamins
riboflavin (B2) and pyridoxine (B6)
what is niacin used to treat
dyslipidemia (lowers VLDL and raises HDL)
what does niacin deficiency cause
glossitis and pellagra
what are the ways in which pellagra can be caused
Hartnup disease (decreased tryptophan absorption), malignant carcinoid syndrome (GI tumors cause tryptophan metabolism to favor serotonin over niacin), isoniazid (decreased B6)
what are the symptoms of pellagra
diarrhea, dementia (and hallucinations), dermatitis (hyperpigmentation of sun-exposed areas), death (within 4-5 years)
what results from excess niacin
facial flushing (induced by prostaglandin, not histamine), hyperglycemia, hyperuricemia
what is the function of vitamin B5 (pantothenate)
essential component of coenzyme A (CoA) and fatty acid synthase
what results from pantothenate deficiency
dermatitis, enteritis, alopecia, adrenal insufficiency
what is the function of vitamin B6 (pyridoxine)
converted to pyridoxal phosphate, a cofactor used in transamination (e.g. AST, ALT), decarboxylation rxns and glycogen phosphorylase
what important molecules depend on pyridoxine for their synthesis
cystathionene, heme, niacin, histamine, neurotransmitters (5-HT, Epi, NE, dopamine, GABA)
what results from pyridoxine deficiency
convulsions, hyperirritability, peripheral neuropathy, sideroblastic anemias due to impaired hemoglobin synthesis and iron excess
what drugs must pyridoxine be coadministered with to prevent side effect of B6 deficiency
isoniazid and oral contraceptives
what is the function of vitamin B7 (biotin)
cofactor for carboxylation enzymes (pyruvate carboxylase, acetyl-CoA carboxylase, propionyl CoA carboxylase)
how common is biotin deficiency
very rare
what results from biotin deficiency
dermatitis, alopecia, enteritis
what are two causes of biotin deficiency
antibiotic use, excessive ingestion of raw egg whites (avidin in egg whites binds biotin)
what is the function of vitamin B9 (folic acid)
converted to tetrahydrofolate, a coenzyme for methylation reactions and 1-carbon transfer reactions;
important for synthesis of nitrogenous bases for DNA and RNA
what are sources of folate and where is folate absorbed in the GI tract
“foliage” (green, leafy veggies); absorbed in jejunum
what results from folate deficiency
macrocytic megaloblastic anemia, hypersegmented PMNs, glossitis, no neurologic symptoms (as opposed to B12)
levels of what molecules are altered with folate deficiency
increased homocysteine, normal methylmalonic acid
when is folate deficiency commonly seen
alcoholism and pregnancy
what drugs can cause folate deficiency
phenytoin, sulfonamides, methotrexate
what function does cobalamin serve
cofactor for homocysteine methyltransferase and methylmalonyl CoA mutase
what are the clinical manifestations of cobalamin deficiency
macrocytic megaloblastic anemia, hypersegmented PMNs; parasthesias, subacute combined degeneration
increased serum homocysteine and methylmalonyl CoA
how do humans get cobalamin and how is it synthesized
found in animal products, symthesized only by microorganisms
list the causes of cobalamin deficiency
decreased intake (veganism) decreased absorption (sprue, enteritis, diphyllobothrium latum) lack of intrinsic factor (pernicious anemia, gastric bypass surgery) absence of terminal ileum (Crohn's)
how do you diagnose pernicious anemia
presence of anti-intrinsic factor antibodies
what are the four functions of ascorbic acid (vitamin C)
- antioxidant
- reduces iron to Fe2+ so it can be absorbed
- hydroxylation of proline and lysine for collagen
- necessary for dopamine beta-hydroxylase, which converts dopamine to NE
