Term
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Definition
| protein degradation to AAs |
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Term
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Definition
| can be interconverted through transamination reactions or catabolized in TCA cycle or ketogenesis |
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Term
| toxic free ammonia groups |
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Definition
| carried as glutamate (or alanine in muscle) to liver where they enter the urea cycle. 2ammonia>urea. |
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Term
| beginning AA metabolism stages |
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Definition
| stomach releases pepsinogen and converts it to pepsin. duo releases CCK and secretin |
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Term
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Definition
| inactive enzyme precursors. major ones released by pancreas: trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase A and B |
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Term
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Definition
| A Small amount is activated by enteropeptidase, an enzyme present on the intestinal wall, which removes the extra AA on trypsinogen to form trypsin, which activates the other zymogens and produces more trypsin |
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Term
| luminal protein degradation is assisted by |
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Definition
| aminopeptidases, which remove one AA at a time at the n-terminus. |
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Term
| systems to transport AA across intestinal wall |
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Definition
| at least 7; monopeptides linked to Na absorption, di- and tri-peptides linked to H+ conc. |
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Term
| t/f mono, di and tripeptides released into the portal circulation |
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Definition
| false - only mono. di and tri are broken down mostly in enterocytes |
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Term
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Definition
| branched-chain AAs: valine, leucine, isoleucine. NOT metabolized by the liver. |
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Term
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Definition
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Term
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Definition
| defective transport of dibasic AA - cysteine, ornithine, arginine, lysine (CORK) - causes low levels of these AA in plasma. increased cysteine in urine causes kidney stones (cystine). |
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Term
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Definition
| poor transport of neutral AAs> plasma tryptophan deficiency> resembles niacin deficiency (like pellagra) -- 4D: diarrhea, death, dermatitis, dementia (and cerebellar ataxia). (other neutral AAs are nonessential) |
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Term
| extracellular proteins are typically degraded by ________ while cytosolic proteins are degraded by _________ |
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Definition
| non-specific lysosomal enzymes / energy-dependent ubiquitin-proteasome system |
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Term
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Definition
| barrel-like structure that non-specifically hydrolyzes AA bonds in cytosol |
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Term
| ubiquitin is excreted/recycled after tagging proteins. regulatory and misfolded proteins have ____ halflife, structural proteins like collagen have ____ halflife |
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Definition
| recycled. minutes vs. months |
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Term
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Definition
| aa with the amino group removed |
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Term
| amino groups are exchanged, allowing excess AAs to be converted to |
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Definition
| alpha keto acids, while donating their amino groups to other alpha keto acids to form new AAs |
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Term
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Definition
| derived from B6, transaminases require this |
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Term
| enzyme for transamination reaction |
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Definition
| transaminase, requires pyridoxal phosphate |
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Term
| basic transamination facts |
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Definition
| reversible, occur in all cells, don't require energy. essential for disposal of excess nitrogen |
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Term
| pyruvate, alpha ketoglutarate, OAA |
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Definition
| all TCA intermediates. >alanine, >glutamate, >aspartate |
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Term
| addition of a 2nd amino group to _ and _ makes |
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Definition
| glutamate and aspartate > glutamine and asparagine |
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Term
| serine is derived from / converted to _ by |
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Definition
| glycolysis intermediate 3phosphoglycerate / glycine, by transferring a carbon to THF |
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Term
| the only nonessential AAs not formed solely from intermediates of glycolysis and TCA, require... |
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Definition
| cysteine and tyrosine - methionine and phenylalanine |
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Term
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Definition
| homocysteine (from met) and serine, reaction requires B6 |
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Term
| phenylalanine hydroxylase |
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Definition
| converts phenylalanine to tyrosine; defective in phenylketonuria |
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Term
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Definition
| thyroid hormone, melanin, fumarate, dopamine, nor, epinephrine |
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Term
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Definition
| caused by deficiency in phenylalanine hydroxylase or sometimes deficiency in cofactor like B4. screened for in newborns. phenyl-alanine, -pyruvate, -lactate, -acetate accumulate. mental retardation, failre to grow walk talk, seizures, hyperactivity, tremor, microencephaly, deficient pigmentation. |
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Term
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Definition
| tetrahydrobioterin - donates an H in hydroxylation of phenylalanine |
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Term
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Definition
| phenylacetate, phenyllactate. give phenylketonuria its name. |
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Term
| what about PKU causes problems? |
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Definition
| excess phenylalanine in blood (hyperphenylalanemia) |
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Term
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Definition
| required for melanin production. inhibited by high levels of phenylalanine. defective in albinism and PKU. |
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Term
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Definition
| lifelong dietary phenylalanine restriction and supplementation with tyrosine. if a patient is pregnant, must be careful or fetus will develop PKU symptoms in first trimester. stopping diet = IQ drop. |
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Term
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Definition
| defective homogentisic acid oxidase causes buildup of homogentisic acid (which normally turns to fumarate). manifests around age 40 with arthritis, black pigmentation of collagen and cartilage and urine (when allowed to sit for a while). treatment - diet low in protein |
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Term
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Definition
| 1. form SAM by adding adenosine (from ATP) to met's sulfur atom. 2. this activates met's terminal methyl group, which detaches to make epi or something. 3. methyl detaching makes SAM into S-adenosylhomocysteine, which is quickly converted to homocysteine. 4. with the help of b6, this condenses with serine to make cystathionine, which cleaves to cysteine and alpha ketobutyrate. |
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Term
| homocysteine can be converted back to methionine by |
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Definition
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Term
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Definition
| homozygous defect in cystathionine beta-synthase, which converts homocysteine to cystathionine. high levels of met and homo in plasma and urine, low levels of cysteine. causes mental retardation, premature arterial disease, osteoporosis, skeletal abnormalities, ectopia lentis. |
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Term
| consuming more (3) might benefit heart and blood vessels by helping metabolize homocysteine |
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Definition
| b6, b12, folic acid (homocysteine theory of atherosclerosis) |
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Term
| BCAA processed by / amino groups removed by / resulting ketoacids> |
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Definition
| peripheral tissues, especially muscle. BCAA aminotransferase. undergo oxidative decarboxylation catalyzed by BCAA dehydrogenase |
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Term
| maple syrup urine disease |
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Definition
| autosomal recessive (often heterozygous) BCAA dehydrogenase defect = BCAAs and their ketoacids accumulate and interfere with brain function, cause feeding problems, vomiting, dehydration, severe metabolic acidosis. |
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Term
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Definition
| lifelong diet of synthetic formula with low levels of BCAA. the thiamine-dependent variant is treated by high doses of thiamine. |
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Term
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Definition
| vasodilator released by degranulating mast cells. mediates allergic and inflammatory reactions. formed from the pyridoxal phosphate-dependent decarboxylation of histidine. |
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Term
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Definition
| present in CNS, intestine and platelets. mediates pain, affect, sleep, body temp and BP. synthesizsed from tryptophan. |
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Term
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Definition
| formed from glycine with contributions from arginine and SAM. phosphorylated>phosocreatine, which can donate P to ADP. |
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Term
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Definition
| muscle-associated enzyme that phosphorylates creatine using ATP. presence of creatine kinase in blood means muscle damage or MI in heart. |
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Term
| total phosphocreatine levels are proportional to |
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Definition
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Term
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Definition
| formed from creatine and phosphocreatine. is proportional to muscle mass. in serum, means kidney failure. low levels in urine means decreased muscle mass. |
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Term
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Definition
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Term
| both keto and glucogenic AAs |
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Definition
| tyrosine iso phenyl trypt. (leu/ly only keto) rest are glucogenic |
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Term
| free ammonia toxic to CNS because |
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Definition
| of its ability to deplete stores of alpha ketoglutarate through formation of glutamate. reduces tca function and energy in cell. |
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Term
| hyperammonemia / treatment |
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Definition
| tremors, slurred speech, somnolence, vomiting, cerebral edema, blurred vision, coma and death / limit protein in diet, administer drugs that bind ammonia and encourage safe excretion |
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Term
| transamination / glutamate dehydrogenase |
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Definition
| 1. nitrogen transferred to alpha ketoglutarate to form glutamate. 2. nitrogen can go to urea cycle in liver mitochondria or directly into urine in kidney. glutamate dehydrogenase can also put nitrogen back ON glutamate (like reaction 1), these reactions use NAD and NADP |
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Term
| in muscle, excess amino groups transferred to... |
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Definition
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Term
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Definition
| alanine aminotransferase. donates the amino group from alanine to alpha ketoglutarate in transamination. is present in hepatocytes. disposes of excess plasma alanine. high levels indicate liver damage. |
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Term
| excess amino groups in peripheral tissues go to |
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Definition
| glutamate to make glutamine, which is then transferred to liver (glutamate is made in liver by transfer of first amino group). |
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Term
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Definition
| functions like glutamate dehydrogenase in releasing an amino group, but from glutamine. amino group goes to carbamoyl phosphate in liver urea cycle or directly to urine in kidney |
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Term
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Definition
| present only in hepatocytes. necessary for final step in urea synthesis. |
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Term
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Definition
| 1. intra-mitochondrial formation of carbamoyl phosphate from NH3 (from glutamate transamination), CO2, and 2ATP. this is the rate limiting step! |
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Term
| carbamoyl phosphate synthetase i |
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Definition
| catalyzes rate limiting step in urea cycle |
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Term
| steps 2 and beyond of urea cycle |
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Definition
| carbamoyl phosphate + ornithine = citrulline, transported to cytosol. combines with aspartate (from OAA by AST) to form argininosuccinate. splits into fumarate and arginine. arginine>urea and ornithine, which goes back to mitochondria. |
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Term
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Definition
| aspartate aminotransferase - high plasma level = liver damage. often in high concentrations in hepatocytes. |
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Term
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Definition
| reforms the OAA that was consumed in creating aspartate for the cycle |
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Term
| OAA + nitrogen transamination = |
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Definition
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Term
| CH3-THF > THF catalyzed by / deficiency |
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Definition
| vitamin B12 (sister reaction to methionine synthesis from homocysteine). deficiency = excess homocysteine, deficient folate = Pernicious Anemia |
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Term
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Definition
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Term
| 2 key pathways to produce glucose |
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Definition
| 1. pyruvate to OAA by mitochondrial pyruvate carboxylase+ATP+CO2, 2. OAA to PEP, then to Glucose by cytoplasmic phosphoenolpyruvate carboxykinase+GTP |
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Term
| when glutamate does transamination, it usually donates a NH3 to |
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Definition
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Term
| NH3 released where directly |
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Definition
| in mitochondria to urea cycle or as ammonia in kidney |
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Term
| deamination can be coupled with transamination to |
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Definition
| remove nitrogen from excess AAs |
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Term
| nitrogen in urea cycle comes from (2) |
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Definition
| aspartate (cytosol) and glutamate (mitochondria) |
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Term
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Definition
| prodrug rapidly converted to phenylacetate, which combines w/ glutamine and is excreted in the urine |
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Term
| describe the path an amino group will take from an AA in muscle to excretion as urea |
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Definition
| nitrogen is transferred to pyruvate to form alanine which goes to liver. ALT forms glutamate and amino group either used to form aspartate via AST to enter urea cycle OR removed by glutamate dehydrogenase |
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Term
| name the two final molecules formed from homocysteine and the vitamins required for these reactions to take place |
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Definition
| met (folate + b12) and cysteine (b6) |
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