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16 Cards in this Set
- Front
- Back
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What enzyme has a vitamin B5 component, Pantothenate?
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Acetyl Coenzyme A
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How many electrons and protons does Nicotinamide Adenine dinucleotide accept? how many does Flavin adenine dinucleotide accept?
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NAD: 2 electrons and 1 proton
FAD: 2 electrons and 2 protons |
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What does TCA take place?
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mitochondrial matrix
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Why does pyruvate need a transporter on the inner mitochondrial membrane but not the outer mitochondrial membrane to get to the matrix?
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the outer membrane contain VDAC but the inner membrane is a barrier so pyruvate must have a transporter to pass this membrane
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What intermediate is made when acetylCo and oxaloacetate undergo an aldol condensation rxn? What enzyme hydrolyzes this intermediate to citrate?
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Citryl CoA
Citrate synthase |
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What is the role of aconitase in the TCA cycle? What is unique about its structure?
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The enzyme causes citrate to undergo isomerization to isocitrate. This is done by first dehydrating citrate to cis-aconitate then hydrating it to isocitrate.
It contains a sulfur cluster |
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Describe the oxidative and decarboxylation performed by isocitrate dehydrogenase.
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Isocitrate is oxidized to the intermediate oxalosuccinate by reducing NAD to release NADH
Then oxalosuccinate is decarboxylated to a-ketoglutarate and CO2 is released |
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What inhibits isocitrate dehydrogenase? What activates it? Which are allosteric substrates?
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inhibitory effect: NADH, ATP
activating effect: isocitrate, NAD+, ADP, Ca++ ADP and ATP are allosteric |
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Describe the 3 domains of a-ketoglutarate dehydrogenase. What inhibits this enzyme?
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E1: a-ketoglutarate dehydrogenase
E2: dihydrolipoyl transsuccinylase E3: dihydrolipoyl dehydrogenase Its products inhibit the enzyme: succinyl CoA, CO2, NADH ....and high energy charge ATP |
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How many ATP are created per NADH?
How many ATP are created per FADH2? How many total ATP are created per acetyl unit? |
NADH--->2.5 ATP
FADH2--->1.5 ATP 10 ATP per acetyl unit |
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Describe the components of the enzyme pyruvate dehydrogenase and what reaction it catalyzed.
Why is it sooooo complex? |
E1=pyruvate dehydrogenase: (cofactor TPP) Rxn: oxidative decarboxylation of pyruvate
E2=dihydrolipoyl transacetylase (lipoamide) Rxn: transfer of acetyl group to CoA E3=dihydrolipoyl dehydrogenase (FAD) Rxn: regeneration of the oxidized form of lipamide Nice to have a crazy complex rxn happen without release of the substrate |
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What substrates control pyruvate dehydrogenase?
What is the internal regulator of this enzyme? |
activating response: AMP, NAD, CoA
inhibitory response: ATP, NADH, Acetyl CoA Internally regulated by phosphorylation: phosphorylated by kinase (in E2) to inactivate PDH. phosphatase removes the phosphate to activate PDH. Things that activate phosphatase: Ca++ (muscle contraction) epinephrine, insulin in LV and adipose |
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Describe Leigh's disease.
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rare inherited disease that impairs mitochondrial fxn which causes chronic lack of energy resulting in motor and CNS problems.
pyruvate dehydrogenase deficiency (E1 problem) causes build up of pyruvate which then in turn is converted to lactate also can be caused by deficiency in phophatase so PDH is always inactive |
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How does a thiamine deficiency affect the TCA cycle? WHat diseases are associated with this?
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Thiamine is a prosthetic group needed in:
pyruvate dehydrogenase a-ketoglutarate dehydrogenase This causes beri-beri (eastern problem) and wet beri beri (associated with alcoholism) |
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How does the TCA cycle replace intermediates used in different rxns?
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anaplerotic rxn
ex) pyruvate carboxylase makes oxaloacetate |
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What intermediates are used to biosynthetic rxns?
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citrate--->FAs
a-ketoglutarate--->glutamate--> GABA or other AAs succinyl CoA--->porphyrin, heme, chlorophyll oxaloacetate--->glucose or ASP-->other AAs |
