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62 Cards in this Set
- Front
- Back
Thiamin active form, and enzymes it is cofactor for
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B 1
thiamin pyrophosphate -pyruvate dehydrogenase -alpha-ketoglutarate dehydrogenase -transketolase (in PPP) |
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Diseases related to thiamin deficiency
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Beriberi
Wernicke-Korsakoff Syndrome (in chronic alcoholics) Symptoms- peripheral neuropathy, fatigue, ataxia, mental confusion, loss of eye coordination |
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Why does thiamin deficiency cause neurological symptoms?
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The brain uses glucose as its source of fuel and by aerobic metabolism only, so interrupting aerobic breakdown of glucose (by preventing it from being converted into pyruvate) affects the brain
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Riboflavin- precursors for?
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B2
flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) |
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Niacin- precursor for?
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B3
NAD and NADP work on malate/lactate dehydrogenases |
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What AA can be converted into niacin? What does niacin deficiency result in?
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Tryptophan
depression, dermatitis, diahrrea assoc. w/pellagra |
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What else is niacin used for?
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given to lower LDL/raise HDL cholesterol
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How many electrons/protons do NAD and FAD carry?
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FAD carries two e-, two H+ (FADH2)
NAD carries two e-, one H+ (NADH + H) |
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Panthothenic Acid
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B5
req'd for synthesis of coenzyme A |
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Structure of CoA?
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adenine, ribose, PP, pantothiene
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CoA function? Where is active site located?
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carrier of acyl groups and fatty acids
terminal sulfhydryl group is reactive site- acyl groups linked here through thioester bond |
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TCA cycle importance
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final common path for generation of energy through oxidation of fuel molecules
most of ATP generated by cells is by conversion of pyruvate to CO2 in TCA, and production of NADH and FADH2 |
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Two stages of conversion of pyruvate to CO2 and H2O
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1. 2 pyruvate--> acetyl CoA via pyruvate dehydrogenase
2. Oxidation of acetyl-CoA to CO2 in TCA cycle |
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3 enzymes involved in PDH complex
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pyruvate dehydrogenase
dihydrolipoyl transacetylase dihydrolipoyl dehydrogenase |
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Coenzymes associated with pyruvate dehydrogenase
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TPP (tightly bound)
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coenzymes w/dihydrolipoyl transacetylase
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lipoic acid (tightly bound)
Coenzyme A (carrier of products) |
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coenzymes w/dihydrolipoyl dehydrogenase
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FAD (tightly bound)
NAD (carrier of products) |
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Step 1 of PDH rxn
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PDH (E1) decarboxylates pyruvate, and the remaining acetyl group is bound to TPP on E1 (to form acetyl/hydroxyethyl TPP)
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Step 2 of PDH rxn
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2 carbon acetyl group is transferred from acetyl-TPP to lipoic acid (the coenzyme of lipoyl transacetylase- E2)
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Step 3 of PDH rxn
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acetyl group transferred from lipoamide to coenzyme A to form acetyl-CoA. lipoamide is left in reduced state (two SH groups)
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Step 4 of PDH rxn
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Lipoamide disulfide is reoxidized by dihydrolipoyl dehydrogenase (E3) with FAD as cofactor to generate FADH2
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Step 5 of PDH rxn
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FADH2 is oxidized by NAD to form NADH + H. NADH will then be oxidized in e- transport chain of mitochondria
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PDH kinase
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inactivates PDH by phosphorylating it
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Activators of PDH kinase
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ATP, NADH, Acetyl-CoA
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Inactivators of PDH kinase
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ADP, NAD, CoA-SH, pyruvate
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PDH phophatase
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removes phosphate from PDH making it more active
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Dysfunctions in PDH complex result in?
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neurological symptoms (other tissues can use FA/AA for fuel, neural tissue uses only glucose)
Increased levels of pyruvate and lactate (and perhaps lactic acidosis if enough accumulates in blood) |
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What part of PDH complex does beriberi occur?
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At E1- b/c no TPP
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Where does arsenic poisoning affect PDH complex?
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As binds sulfhydryls, preventing reoxidation -- acyl group can't bind
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Genetic defects in PDH complex
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similar symptoms to beriberi
usu. due to E1 deficiency |
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Pacemaker of TCA cycle?
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citrate synthase
has large neg. delta G, so drives the cycle forward (hydrolysis of thioester bond yields lots of E) |
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Regulators of IDH (isocitrate dehydrogenase)?
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NADH, ATP (negative allosteric effectors)
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What is meant by TCA is amphibolic pathway?
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contains both anabolic and catabolic processes
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TCA intermediates that can be used in lipid biosynthesis:
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acetyl CoA is primary source of carbons for FA and cholesterol.
Citrate serves as source of Acetyl CoA-- can't travel out of inner mitochondrial membrane on its own, so travels as part of citrate (and then converted via ATP citrate lyase) |
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TCA intermediates that can be used for gluconeogenesis?
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malate and oxaloacetate
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TCA intermediates for AA synthesis?
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alpha-ketoglutarate can be converted to glutamate
oxaloacetate can be converted to aspartate |
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TCA intermediates for porphyrin biosynthesis?
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succinyl-CoA is precursor for the heme group
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Anaplerotic rxns
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Used to replenish supply of oxaloacetate if other intermediates are used up in biosynthetic rxns
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pyruvate carboxylase
fxn, what activates it, what's its coenzyme |
converts pyruvate + HCO3 + ATP--> oxaloacetate + ADP
activated by acetyl-CoA, b/c if there's an oxaloacetate deficit, Acetyl-CoA builds up Biotin is necessary- carries CO2 |
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Transamination anaplerotic rxns
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glutamate--> alpha-ketoglutarate
aspartate--> oxaloacetate |
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Standard reduction potential
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the tendency of a chemical species to lose or acquire electrons
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Favorable reduction reactions pos or neg delta E?
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positive (and thus a negative delta G)
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Equation of redox rxns?
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G=-nFE
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What is a cytochrome? What form is Fe in? What are cytochromes a,b,c like?
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A protein w/a tightly bound heme group. Fe can either be in Fe+2 or Fe+3 form. A,B cytochromes are integral membrane proteins. C is smaller, more mobile
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Complex I: protein component and prosthetic groups
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NADH CoQ oxidoreductase
FMN, Fe-S |
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Complex II
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succinate CoQ oxidoreductase
FAD, Fe-S, heme b |
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Complex III
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CoQ cytochrome C reductase
cytochromes b and c, Fe-S |
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Complex IV
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cytochrome c oxidase
Cu2+, heme a |
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Amytal
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inhibits complex I between flavoprotein and ubiquinone
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Rotenone
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inhibits transfer of e- in complex I from Fe-S to ubiquinone
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Antimycin A
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blocks chain at complex III
produced by streptomyces bact ingredient in fintrol |
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Cyanide
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blocks complex IV by binding to iron in the Fe-S complexes of cytochrome C oxidase
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CO and sodium azide
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also inhibit complex IV
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proton motive force
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refers to chemical (more H+s on one side) and electrical (separation of charge- more positive on outside) gradients generated by pumping of protons during ETC
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ATP synthase structure
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Fo portion - protons pass through, rotate around C ring, and finally back into matrix
F1 portion- 3alpha 3 beta subunits that don't rotate beta have binding sites for ADP+P |
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ATP synthase function
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As H+ attach to Cs in ring, the ring rotates causing conformational changes in beta binding sites
open- ADP + P attach loose- ADP/P bound loosely tight- conversion to ATP open- ATP leaves, another ADP+P enter |
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How many protons required for ATP synthesis?
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4 per ATP
so NADH can produce ~3ATP, FADH2 can produce ~2ATP |
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G3P shuttle
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dihydroxyacetone picks up 2Hs from NADH+H to form G3P. G3P dehydrogenase reoxidizdes G3P to dihydroxyacetone and transfers e- to FAD to make FADH2 on inside of mitochondria. This is not as efficient, since an NADH is replaced by an FADH2, which enters the ETC later
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Malate-aspartate shuttle
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OAA + NADH-->NAD + malate
malate passes through membrane Malate-->OAA + NADH via malate dehydrogenase OAA gains amino group from glutamate, forming aspartate and alpha ketoglutarate. Aspartate travels through membrane, and is then converted back to OAA |
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UCP1
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mitochondrial membrane uncoupler - found in brown fat of mammals, involved in heat production during hibernation
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2,4 dinitrophenol
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uncoupler at inner mitochondrial membrane
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oligomycin
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ATP synthase inhibitor, works at Fo portion
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