Biochemistry 4th Lecture - Biological Oxidation

Biological oxidation The ATP Cycle High energy bonds Phosphoanhydrite – large negative ΔG of hydrolysis, high energy bonds represented by “~”. Phosphocreatine (creatine phosphate) – must know structure. Used for storage of ~P bonds. Catalyzes reaction: creatinephosphate + ADP <--> ATP + creatine. Phosphoenolpyruvate (PEP) – converts ester to ketone Other example for phosphate esters: linkage between glucose-6-phosphate A thioester formes between a carboxylic acid and a thiol (SH), e.g, the thiol of coenzyme A. Thiol of coenzyme A can react with carboxyl group of acetic acid – acetyl-CoA. Coenzyme A contains ADP – 3' – phosphate. Pantothenate. Functional group – thiol group βmercaptoethylamine. Roles: • • •

energy transfer and storage: ATP, PPi ,polyphosphate, creatinephosphate Group transfer: ATP, coenzyme A Transient signal: cAMP

Oxidation and reduction: In organic chem = dehydrogenation. Catababolism is oxidative Anabolism is reductive NAD+ Nicotinamide adenine dinucleotide nicotinamide ring accepts 2 e and H+ and goes to reduced state (Must know structures). FAD Flavin adenine dinucleotide ATP can form on the substrate level (direct) and by oxidative phosphorelation. Respiratory Chain • • •

Electron transport: carried by reduced coenzyme Oxidative phosphorelation At inner mitochondrial membrane

Electron transport • Four protein complexes • coenzymes + shuttle

Must know: complexes + coordinating product. ATP contains: F1 part (α3, β3, γδε), F0 part Important: what is the P/O ratio? Inhibitors of oxidative phosphorylation rotenone inhibits complex-1 cyanide, azide and CO inhibits complex 4 oligomycin inhibit ATP synthesis.