citric acid cycle

Reaction 1

Enzyme: citrate synthase

Oxaloacetate + Acetyl CoA —— citryl CoA —-- citrate

Purpose : bring new carbons into the citric acid cycle

IRREVERSIBLE

Reaction 2

Enzyme: aconitase

citrate — isocitrate

Purpose : moving hydroxyl to C2, create a secondary (2°) alcohol so that electrons can be generated in the subsequent reaction.

Reaction 3

Enzyme: isocitrate dehydrogenase

isocitrate —- oxalosuccinate —- alpha-ketoglutarate

Purpose : directly generate electrons for electron transport

IRREVERSIBLE

Reaction 4

Enzyme: alpha-ketoglutartate dehydrogenase complex

alpha-ketoglutarate —- succinyl CoA

Purpose : directly generate electrons for electron transport.

IRREVERSIBLE

Reaction 5

Enzyme: succinyl CoA Synthetase

succinyl CoA —- succinate

Purpose: produce a molecule of ATP by substrate level phosphorylation.

Reaction 6

Enzyme: succinate dehydrogenase

succinate —- fumarate

Purpose: directly generate electrons for electron transport.

inner mitochondrial matrix, electron transport complex II

Reaction 7

Enzyme: fumerase

fumarate —-- malate

Purpose: create a secondary (2°) alcohol so that electrons can be generated in the subsequent reaction.

Reaction 8

Enzyme: malate dehydrogenase

malate —- oxaloacetate

Purpose: directly generate electrons for electron transport.

What substrates are biosynthetic precursors?

oxaloacetate, citrate, alpha-ketoglutarate, succinyl CoA