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79 Cards in this Set

  • Front
  • Back
Thiamine activation
-what makes it active
Product = Thiamine Pyrophosphate
Enzyme = Thiamine pyrophosphokinase
Active b/c it contains a very reactive Carbanion
TPP Enzymes (4)
-a-KG Dehydrogenase
-Branched chain a-KA Dehydrog
Thiamine deficiency (3 types)
-Infantile - heart problems
-Dry - anorexic, weak
-Wet - edema/dilated heart
Thiamine neurotransmitters:
Riboflavin activation
Product = FMN or FAD
Enzyme = Riboflavin kinase
Substrates = 2 ATP
FMN function
FAD function
Coenzyme for dehydrogenase or oxidase enzymes
TCA cycle enzymes w/ FAD:
-PDH Dehydrogenase
-aKG Dehydrogenase
-Succinate dehydrogenase
Amino acid degradation enzymes w/ FAD:
Branched chain a-KA Dehydrogenase
FA Degradation enzymes w/ FAD:
-AcCoA Dehydrogenase
-B-hydroxyacyl CoA Dehydrog
3 other enzymes that need FAD:
-GlycerolP Dehydrogenase (mito)
-Coenzyme Q
-NADPH Dehydrogenase
What purine catabolism enzyme needs FAD?
Xanthine dehydrogenase
What amino acid precursor uses FAD to make a potentially oxidative toxic product?
Nitric oxide synthase
Symptoms of Riboflavin deficiency
-Mouth problems
Niacin is used for what molecules:
Another name for niacin
Nicotinic acid
3 Sources of NAD/NADP:
-Niacin/Nicotinic Acid
3 cofactors needed to make NAD from Tryptophan:
-TPP (B1)
-PLP (B6)
-FAD (B2)
3 uses of NADPH:
-GSH reductase
-Cyp 450
-NADPH Oxidase
3 symptoms of Niacin deficiency:
3D's for B3:
Pantothenic acid is in what:
Coenzyme A
Reactive component of Coenzyme A:
-Mercaptoethanol - SH
Role of Pantothenate in CoA:
-Makes the core between mercaptoethanol and rest of it.
When do you see pantothionate deficiency?
Rarely - if patients treated with metabolic antagonists.
3 forms of Pyridoxal Vit B6:
-Pyridoxine (C-OH)
-Pyridoxal (HC=O)
-Pyridoxamine (H2NC=O
How is pyridoxine activated/ what enzymes are necessary:
-Kinase to phosphorylate to PLP
-Oxidase to convert from Pyridoxine or Pyridoxamine to Pyridoxal
Active form of Vit B6:
Pyridoxal Phosphate - PLP
Main gist of PLP's function:
Breaks alpha Carbon bonds in one of 3 ways
What 3 bonds are broken by PLP?
What type of enzyme does each type?
1. C-COOH (decarboxylase)
2. C-H (aminotransferase or dehydratase)
3. C-CH2R (hydroxymethyltransferase or aldolase)
2 functions of PLP that don't involve breaking a-C bonds:
1. Substrate binding (Cys synth)
2. General acid catalyst
What enzyme uses PLP as a general acid catalyst?
Glycogen phosphorylase - this is an unusual use of PLP
What enzyme uses PLP for substrate binding?
Cystathione Synthetase
What dehydratases use PLP?
Serine Dehydratase
Threonine dehydratase
What is Biotin's function ALWAYS?
transfer of a CO2 to a substrate
What 3 enzymes are required for getting Biotin to a functional state in the body after diet?
1. Proteinase/exopeptidase
2. Biotinidase
3. Biotin ligase
What is Biotinidase for? What does it produce?
Frees Biocytin from protein
Products: Biotin + Lysine
What is Biotin Ligase for?
Activating Biotin to the enzyme:
2-step reaction adds AMP, then replaces it with H2N-Carboxylase enzyme
After catalyzing a CO2 transfer how is Biocytin recycled?
Again by Biotinidase
What is a symptom of Biotin deficiency?
What enzyme is needed for folate absorption from the diet?
Folate hydrolase
What occurs during Folate absorption from the diet?
1. Polyglutamication
2. Removal of all but one glutamate from Folate by Folate Hydrolase
What form of folate can be absorbed by enterocytes?
Monoglutamic Folate
What happens after monoglutamic folate gets into the enterocyte?
It is bound by Folate Binding Protein FBP and sent to circulation.
What is required for folate to be active?
1. Folate reductase / NADPH
2. Dihydrofolate Reductase / NADPH
What is the product of folate activation?
Tetrahydrofolate - THF
What is an important inhibitor of Folate Reductase?
What pathway does Folate function in?
Folate 1-Carbon pathway
What other B vitamins are needed by the Folate 1C pathway?
B12 - cobalamin
B6 - PLP
Why does the folate 1C pathway need cobalamin?
Methionine Synthase
Why does the Folate 1C pathway need PLP?
Serine Hydroxymethyl Transferase
What are the amino acids that donate carbons to the 1CP?
What intermediates are made by:
Histidine = N10FormylTHF
Ser/Gly = N5-methyleneTHF
What is the role of Methionine in the 1CP?
It uses a carbon from Methyl THF to make methionine
What is the reaction catalyzed by Methionine synthase?
Homocysteine + Methyl THF makes SAM (s-adenosylmethionine)
What results from folate deficiency?
Neural Tube Defects
Macrocytic anemia
Glossitis/Slick tongue/Pallor
GI Atrophy and Heart Disease
What is the effect of either:
-Folate deficiency
-Vit B12 deficiency
Purine and dTMP synthesis is inhibited!
What will result if dTMP and Purine synthesis is too low?
Macrocytic anemia
How does Vit B12 deficiency inhibit dTMP/Purine synthesis?
Because Vit B12 is a cofactor for Methionine Synthase, which gives a byproduct THF-methylene. THF-methylene is necessary for making dTMP.
How does Vit B12 deficiency cause Folate deficiency?
When Methionine Synthase is not working Folate gets trapped as 5-methyl THF
What THF molecules contribute to
-Purine synthesis?
-dTMP synthesis?
-N5N10-methenyl THF
-N10-Formyl THF
N5-N10 methylene THF
What THF molecule is made by -Histidine?

Histidine -> N5-Formimino THF

Ser/Gly -> N5,N10-Methylene THF
What 1CP enzymes use folate?
-Dihydrofolate Reductase
-Tetrahydrofolate Reductase
-Serine hydroxymethyl transfrase
-N10-Formyl THF synthetase
What SAM cycle enzyme requires folate?
Methionine synthase
What amino acid degradation enzyme uses Folate?
Glutamate formimino transferase
What enzymes use folate in:
-Purine biosynthesis
-Pyrmidine biosynth
Purine: Formyltransferase

Pyrimidine: Thymidylate synthase
What are symptoms of Vit B12 deficiency?
Same as for folate, in addition to neurological symptoms.
What are major causes of Vit B12 deficiency?
-Pernicious anemia (Intrins. Fx)
-Poor absorption in elderly
-Long term vegetarianism
How is Vit B12 absorbed from the gut?
1. IF binds cobalamin
2. Cobalamin-IF binds Cubilin receptor on ilium
3. Cobalamin is transferred to Transcobalamin II
4. Complex is released to circulation
Where does Transcobalamin II go?
To target cells to bind Megalin receptor for uptake
What are the 2 targets for Vit B12 inside the cell?
Binding to:
-Methylmalonyl CoA mutase
-Methionine synthase
What reactions require Vit B12?
Homocysteine --> Methionine

MethylmalonylCoA -> SuccinylCoA