Chemistry 2100 Chapter 27

Metabolism Metabolism is the sum of catabolism and anabolism. 2

Metabolism

digestion: hydrolysis degradation: nutrients acetyl CoA TCA Cycle: acetyl CoA CO 2 + NADH / FADH 2 oxidative phosphorylation: NADH / FADH 2 ATP Stages of Catabolism

Catabolic Pathways Two principal types of compounds participating in the common catabolic pathway are: –AMP, ADP, and ATP: agents for the storage and transfer of phosphate groups. –NAD + /NADH and FAD/FADH 2 : agents for the transfer of electrons in biological oxidation-reduction reactions

Ad Adenosine Triphosphate

H 2 O 31.4 kJ/mol OPOPOPO O O O O O O Ad OPO O O OPOPO O O O O ++

Coupled Reactions (and why we need them)

+++RC O OHHOR'RC O O 16.7 kJ/molH 2 O

RC O OH+10.5 kJ/molOPOPOPO O O O O O O Ad RC O O O O OPOPOPO O O O O + +

RC O O O O OP O O O OP kJ/mol HOR' RC O O

RC O O HO RC O OH+ATP +AMP +PP kJ/mol +

NAD + /NADH –NAD + is a two-electron oxidizing agent, and is reduced to NADH. –NADH is a two-electron reducing agent, and is oxidized to NAD +. The structures shown here are the nicotinamide portions of NAD + and NADH. –NADH is an electron and hydrogen ion transporting molecule.

FAD/FADH 2 –FAD is a two-electron oxidizing agent, and is reduced to FADH 2. –FADH 2 is a two-electron reducing agent, and is oxidized to FAD. –Only the flavin moiety is shown in the structures below.

Acetyl-CoA production

Acetyl-CoA Oxidation

Electron Transfer and Oxidative Phosphorylation

Where does this all happen?

Net Effect of the Citric Acid Cycle Acetyl-CoA + 3NAD + + FAD + GDP + P i + 2 H 2 O 2CO 2 +3NADH + FADH 2 + GTP + CoA + 3H + carbons of acetyl groups in acetyl-CoA are oxidized to CO 2 electrons from this process reduce NAD + and FAD one GTP is formed per cycle, this can be converted to ATP intermediates in the cycle are not depleted

Energy Yield

Oxidative Phosphorylation