Before entering the citric acid cycle, glucose and fatty acids are degraded to acetyl groups of acetyl-CoA

in this case, glucose product pyruvate is oxidized to  CO2 and acteyl-CoA by PDH complex

• Multiple copies of the three enzymes in the system
• Five cofactors (four from vitamins) are involved in pyruvate oxidation to acetyl coa

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• Pyruvate oxidized - CO2 and Acetyl-CoA
• oxidative decarboxylation
• NADH formed- eventually gives hydride ion (which has two electrons) to respiratory chain oxygen
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• Thiamine pyrophosphate (TPP)- thiamine
• Flavin adenine dinucleotide (FAD)-riboflavin
• CoA-SH -pantothenate
• Nicotinamide adenine dinucleotide (NAD)-niacin
• lipoate

• Reactive thio group used to make CoA an acyl carrier
• linked acyl groups are called thioesters
• when bound to coA, high transfer potential of acyl group and high std free energy of hydrolysis = donate acyl to acceptor molecules[image]

• two thiol groups can undergo reversible oxidation to s-s bond
• because of redox potential, can be electron carrier (H:) or acyl carrier
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• Pyruvate dehydrogenase (E1) -TPP bound
• Dihydrolipoyl transacetylase (E2)- liopate attaches here and linking binding domains
• Dihydrolipoyl dehydrogenase (E3)- FAD bound

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1. c-1 released as CO2, c2 attaches to TPP (hydroxyethyl TPP). slow step
2. Hydroxyethyl group oxid. to acetate. trasferred to lipoate. electrons from oxid. reduce the s-s of lipoate on E2 to -SH
3. transesterification of acetyl to CoA= Acetyl-CoA
4. previously reduced lipoyl grps(-SH) in E2 transfer H's to FAD in E3(form FADH2), restoring s-s
5. E3 FADH2 loses H- to NAD+ = NADH

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NAD structure  and function

what types of groups does it oxidize?

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