lecture 12 pyruvate dehydrogenase Flashcards
after glycolysis, what occurs?
pyruvate –> acetyl coA to power the citric acid cycle
where does the oxidation of glucose occur
mitochondria
Conversion of pyruvate to acetyl CoA occurs in the ___
Conversion of pyruvate to acetyl CoA occurs in the mitochondrial matrix
how does pyruvate dehydrogenase link glycolysis with cellular respiration?
by converting pyruvate into acetyl coA
describe where glycolysis occurs
cytoplasm
where is glycolysis vs pyruvate oxidation?
pyruvate —> acetyl coA (we call this pyruvate oxidation) occurs in mitochondrial matrix
once we have oxidized pyruvate, where do we need to send our acetyl coA for the citric acid cycle?
the citric acid cycle takes place in the matrix of themitochondria
why is pyruvate oxidation a crucial junction in metabolism?
This reaction is an irreversible link between glycolysis and the citric acid cycle
describe what pyruvate dehydrogenase does
the pyruvate dehyrogenase complex, a complex mitochondrial matrix enzyme, oxidatively decarboxylates pyruvate to form acetyl CoA.
how many enzymes comprise the pyruvate dehydrogenase complex?
3
T/f: pyruvate dehydrogenase complex has multiple enzymes, each with its own co-factor and prosthetic group
true
The synthesis of acetyl CoA from pyruvate consists of three steps:
- Decarboxylation to remove CO2
- Oxidation to form an energy-rich (thioester with lipoic acid chain) bond
- Transfer onto Coenzyme A (also a thioester). Co A carries acetyl units with a high energy bond (high transfer potential)
what happens to acetyl coA once in the TCA
Acetyl CoA will either be oxidized to CO2 (catabolic fate) or be used to synthesize lipids (anabolic fate).
Co A carries acetyl units with a ___ energy bond due to ___
high energy bond; high transfer potential
Overall reaction pyruvate oxidation
pyruvate + coA + NAD+ –> acetyl coA + CO2 + NADH + H+

describe what happens to pyruvate in this process
remove COO group, then remove some electrons to give it a positive charge. now its an ‘acetyl’ group : O=C-CH3. stick it on coA to make acetyle coA
what’s special about the bond formed when you put acetyl on coA?
forms a high energy thioester bond
what is the lipoamide arm and what does it do?
a long arm in the pyruvate dehydrogenase that is covalently attached to the amide group of lysine
it reacts with the acetate that was formed by the decarboxylation and carries it from active site to active site so that the reactions are made more efficient and occur more quickly
T/F: The PDG is regulated by covalent modification and by allosteric effectors
true
Regulation of the PDG enzyme has to do with :
Energy charge and availability of pyruvate and acetyl coA
Response of the pyruvate dehydrogenase complex to the energy charge
The pyruvate dehydrogenase complex is regulated to respond to the energy charge of the cell. (A) The complex is inhibited by its immediate products, NADH and acetyl CoA, as well as by the ultimate product of cellular respiration, ATP. (B) The complex is activated by pyruvate and ADP, which inhibit the kinase that phosphorylates PDH.
T/F: The transformation of malate to oxaloacetate can occur in the cytoplasm as well as the matrix of the mitochondrion.
true! you have to turn OA into malate to get it back to OA. you have it in the cytoplasm and need it back in the matrix