Chapter 18 - Pyruvate Dehydrogenase Flashcards
3 stages of cellular respiration
- acetyl CoA synthesis
- citric acid cycle
- electron transfer/oxidative phosphorylation
acetyl CoA
fuel of citric acid cycle; major source of metabolic energy
pyruvate dehydrogenase complex (PDH) present it..
mitochondria
cofactors
- helper molecules
- non-protein, usually made up of vitamins
- bound to an enzyme
- required for catalysis
- do not catalyze
PDH cofactors
- thiamine pyrophosphate (TPP)
- lipoic acid
- coenzyme A
- flavin adenine dinucleotide (FAD)
- nicotinamide adenine dinucleotide (NAD+)
how does Coenzyme A attach to things?
reactive thiol group
TPP is derived from..
vitamin B1
Where does TPP bind to PDH?
E1
TPP to acetyl CoA
accepts 2 carbon backbone after decarboxylation to result in hydroxyethyl TPP intermediate
lipoid acid role
bind to E2; accepts hydroxyethyl TPP to form energy-rich thioester bond
NADH and FADH2 roles
electron carriers; carry 2 e-
oxidized form of lipoid acid
disulfide bond
reduced form of lipoid acid
hydrogenated sulphur
acetylated lipoid acid
1 hydrogenated, 1 attached to acetyl group..?
Summarize PDH and synthesis of Acetyl CoA
- pyruvate converted to acetyl CoA by PDH complex
- E1: oxidative decarboxylation of pyruvate and transfer of 2 carbon unit to E2—> hydroxyethyl TPP
- E2: transfer of acetyl moiety to CoA to synthesize Acetyl CoA
- E3: regenerates oxidized lipoid group of E2 and transfers protons and e- to FAD and then NAD+ to complete cycle
3 enzymes
- pyruvate dehydrogenase
- dihydrolipoyl transacetylase
- dihydrolipoyl dehydrogenase
regulation of PDH
- products NADH, acetyl CoA, ATP inhibit
- pyruvate and ADP activates (by inhibiting kinase that phosphorylates PDH)
kinase
inactivates active PDH by adding phosphate group in presence of ATP
phosphatase
activates inactive PDH by removing phosphate group and releasing Pi
