Citric Acid Cycle = Tricarboxylic Acid Cycle = Krebs Cycle – Plays a central role in metabolism of living organisms. It is a major cycle for making energy (ETC and glycolysis) and making building blocks for biosynthesis. Other biomolecules feed into the TCA cycle: fatty acids, many amino acids, acetyl CoA, pyruvate and more. Supply curved arrows to show the flow of electrons in each step.

O alanine O glucose cysteine (gluconeogenesis) glycine serine O O pyruvate glucose threonine (glycolysis) tryptophan lactate OH O phosphoenol purines aspartate pyruvate glucose pyrimidines

O O citrate synthase H2O O malate O S-CoA O dehydrogenase fatty acids, 10 sterols O O O 1a O O oxaloacetate 1b + O NADH + H O O NAD+ O aspartate asparagine citrate OH O malate OH O fumarase 2 aconitase 9 O +H2O O O O O phenylalanine O O tyrosine Citric Acid Cycle (Kreb's Cycle) O O fumarate O (V2, p 539, p 600) cis-aconitate Oxaloacetate Cycle FADH succinate 8 2 dehydrogenase 3 O FAD OH O O O O

succinate O GTP O O O O CoA-SH GDP + Pi isocitrate 7a-c succinyl-CpA O 4 synthetase O S-CoA NAD+ O NADH + H+ O O NADH + H+ succinyl-CoA O NAD+ O O O O O porphyrins 6a-e 5 oxalosuccinate -ketoglutarate O O heme lsoleucine dehydrogenase methionine CoA-SH valine O O -ketoglotarate CO2 isocitrate dehydrogenase CO2 CoA-SH

glutamate

arginine glutamine histidine proline

Y:\files\classes\Bio-Org Game related Examples\biochem cycles\cycle Citric Acid Cycle 2 web.doc O 1a B H CoA O CoA O S BH S acetyl CoA O OH HO OH HO O O BH oxaloacetate O O B H

H H 1b B O O O CoA H CoA H S H B O S O O

OH OH HO HO

O O O O citrate H H

O OH 2 B O H H B O OH OH HO OH O O O citrate O OH H cis-aconitate H B B

3 B H H O BH OH

O OH O OH

OH O OH O O OH H B O OH B cis-aconitate isocitrate

4 B H N R BH O O H O OH H O OH N R NAD+ H OH O OH O O OH O OH NADH oxalosuccinate (unstable) isocitrate

Y:\files\classes\Bio-Org Game related Examples\biochem cycles\cycle Citric Acid Cycle 2 web.doc 5 BH O B O O OH O OH

OH O O O O C OH O H B O -ketoglutarate H B oxalosuccinate (unstable)

R R B 6a BH N N O H O S O OH O OH S

OH O TPP ylid -ketoglutarate OH O

R R N 6b N H B H O S S O O O B H O O C OH OH O H O

R 6d N R S S N R R SH S SH O O S O O TPP ylid OH H OH B BH

FAD 6e BH lipoamide + FADH2

B B SH BH S CoA R O R SH SH H S O O CoA S O OH succinyl CoA OH

Y:\files\classes\Bio-Org Game related Examples\biochem cycles\cycle Citric Acid Cycle 2 web.doc 7a O succinyl CoA O O O P OH O O CoA O OH H CoA O P S S O OH OH O B H B

O 7b O O O O GDP O O OH H P O O P O GTP O OH succinic acid OH O O

BH B

8 B O H H O succinic acid BH fumaric acid O H O O H O H OH H H OH N N

O N O N FAD B BH H FADH2

9 BH O B O O H O O H O OH O OH OH H H B H B fumaric acid malic acid

10 N R BH B H O O O O H H NAD+ O N R O H H O H O OH OH oxaloacetate malic acid NADH

Y:\files\classes\Bio-Org Game related Examples\biochem cycles\cycle Citric Acid Cycle 2 web.doc