Question | Answer |
Can vitamins be synthesized in the human body | no |
Two classes of vitamins | water-soluble and fat-soluble |
Fat soluble vitamins | A,D,K,E |
Water soluble vitamin classes | b vitamins, folic acid and ascorbic acid (C) |
B vitamins | thiamine (B1), Riboflavin (B2), Niacin (B3), Pantothenic Acid (B5), Pyridoxine (B6; pyridoxal; pyridoxamine), biotin (B7), B12 (cobalamine) |
Sources of vitamins | food intake and synthesis by intestinal microorganisms |
6 ways to have vitamin deficiency | inadequate dietary intake, inadequate absorption, inadequate use (inadequate conversion), increased requirements, increased excretion, drug-associated deficiency |
thiamine cofactor/s, reaction/s, and disease/s | thiamine pyrophosphate; pyruvate DH, alpha ketoglutarate DH, branched chain alpha keto acid DH; Beriberi |
riboflavin cofactor/s, reaction/s, and disease/s | FAD, FMN;oxidation-reduction;no disease |
Niacin cofactor/s, reaction/s, and disease’s | NAD, NADP; oxidation-reduction; pellagra |
Pantothenic acid cofactor/s, reaction/s, and disease/s | Coenzyme A; acyl transfer, pyruvate DH, alpha keto glutarate DH; no disease |
What B vitamin can be made in small amounts in the body | niacin (made from tryptophan) |
Pyridoxine cofactor/s, reaction/s, and disease/s | pyridoxal phosphate; transamination, decarboxylation, dehydration; seizure in infants |
Cobalamin cofactor/s, reaction/s, and disease/s | 5’-deoxyadenosylcobalamin, methylcobolamin; methylmalonyl-CoA mutase, 5’methylTHF homocys transferase; pernicious anemia and others |
Folate cofactor/s, reaction/s, and disease/s | tetrahydrofolate; 1 C transfer, dTMP biosynthesis, purine synthesis; megaloblastic anemia and others |
Biotin cofactor/s, reaction/s, and disease/s | no cofactors; carboxylation; no disease |
Ascorbic acid cofactor/s, reaction/s, and disease/s | ascorbid acid; hydroxylation (collagen); scurvy |
Beriberi | thiamine deficiency; mostly in areas that used polished rice; lethargy, weight loss, irregular heart rate, convulsions, death |
Pellagra | niacin deficiency; dermatitis, diarrhea, dementia, death |
Most common vitamin deficiency | folic acid |
Normal folic acid requirement | 100-200 mg/day/adult (more for pregnant women) |
Causes of folic acid deficiency | inadequate intake, impaired absorption (intestinal diseases), impaired metabolism, increased demand |
Diagnosis of folic acid deficiency | ingest test dose of Histidine and test forminimoglutamate level in urine; if there is forminimoglutamate in urine, folic acid deficiency is present |
Consequences of folic acid deficiency | 7 weeks-nothing; 13 wks-formiminoglutamate in urine, altered read blood cells; 4 months-irritability, forgetfulness, anemia; upon addition of folic acid, everything normalized |
Biochemical consequences of folic acid deficiency | defective glycine cleavage (neurological problems), defective homocys (met conversion->neurological defects); defective purine/pyrimidine synthesis (DNA and hematopoietic defects) |
B12 deficiency comes from | impaired absorption |
B12 storage | up to 6 years in liver |
B12 absorption | parietal cell in stomach makes instrinsic factor (IF) which binds B12 and transports it to the ileum; transported in blood by TC (transcobalomine) which takes it to the liver |
Pernicious anemia | IF (intrinsic factor) deficiency through impaired absorption of B12 |
Affects of pernicious anemia | impaired: regeneration of tetrahydrofolate pool, impaired purine/dTMP biosynthesis, hematopoietic defects, neurological defects |
Neurological defects of pernicious anemia | accumulation of methylmalonyl CoA intereferes with myelination of nervous tissue b/c methylmalonyl CoA is a competitor of malonyl CoA in FA synthesis |
Treatment for pernicious anemia | intramuscular B12 injection and folate supplement |
N metabolism consequences of THF deficiency due to B12 deficiency | defective: purine/pyrimidine synthesis, glycine cleavage |
N metabolism consequences from direct B12 difficency | defective: homocys->Met conversion, methylmalonyl CoA->succinyl CoA conversion |
B12 and THF correlation | B12 is necessary in THF regeneration |
5 groupings of biosynthesis of non-essential AA | 1)Ala, Asp, Glu, Gln, Asn 2)Arg, Pro 3)Ser, Gly 4)Tyr 5)Cys |
alanine synthesis | pyruvate transamination |
aspartate synthesis | oxaloacetate transamination |
glutamate synthesis | alpha ketoglutarate transamination |
glutamine synthesis | add ATP and NH3 to glutamate |
asparagines synthetase | add ATP and N to aspartate |
Arginine and proline synthesis | glutamate->glutamate semialdehyde->proline and arginine |
Tyrosine synthesis | phenylalanine hydroxylase; 3/4 of Phe in diet goest to Tyr |
Cystein synthesis | comes from cystathionine which comes from serine and homocysteine which comes from methionine; cystathionine goes to cysteine and alpha ketobutyrate |
Serine synthesis | 3-phosphoglycerate (phosphogylcerate) 3-phosphopyruvate (aminotransferase) 3-phosphoserine (phosphatase) serine |
Glycine synthesis | serine (serine hydroxymethyl transferase) glycine; the rxn uses N5N10methylene THF which becomes THF; THF returns to N5N10 through a rxn with another glycine |
Almost all non-essential AA’s can be synthesized from | glycolysis products |