Transcript Chapter14
Fundamentals of Biochemistry Third Edition Donald Voet • Judith G. Voet • Charlotte W. Pratt Chapter 14 Introduction to Metabolism Copyright © 2008 by John Wiley & Sons, Inc. This final is going to be hard!! Just kidding!! Terms • • • • • • Catabolic – degradation Anabolic – synthesis Autotrophs – (Latin – self, feeder) Heterotrophs (other, feeder) Aerobes – use oxygen Anaerobes – oxidize without oxygen Thermodynamics • Remember that ΔG°’ = -RT lnKeq – Therefore, concentration is very important – If reactants are close to equilibrium concentration, ΔG will be zero. • Therefore, both forward and reverse reactions can happen equally. • Not all reactions happen close to equilibrium – Enzymes not close to equilibrium are irreversible – If a pathway has ONE irreversible step, the entire pathway is irreversible Flux • The rate of flow of metabolites through a pathway – One step is always committed (irreversible) • Remember, living things are at steady state, not equilibrium • J(flux of metabolite) = vf - vr – Rate of flux for irreversible step if rate of forward rxn – Slowest step usually controls flux of a pathway – Sometimes multiple enzymes control flux of pathway • Control – – – – Allosteric Covalent modification Substrate cycles Genetic control High-energy intermediates store energy to drive endergonic reactions Phosphocreatine can transfer a phosphate to ADP ATP + creatine ↔ phosphocreatine + ADP ΔG°’ = 12.6 kJ/mol Another high energy bond is the thioester bond. This is used in carbohydrate, protein, and fatty acid metabolism with acetyl-CoA Redox reactions • The majority of energy is supplied via redox reactions. • Ultimately, oxidation results in the movement of electrons to oxygen. • This requires carriers of the electrons Redox reactions can be separated into half-cells to create a battery. Batteries do word, therefore we can calculate the work (or free energy change) of redox reactions Aoxn Bred Ared Boxn Ared Boxn G G' RT ln n Aox Bred G w' wel wel nE G nE RT Ared Boxn n E E ' n Aox Bred NOTE: positive E results in -ΔG Using Table 14-5, calculate the free energy change for the reaction NADH + FAD + H+ → NAD+ + FADH2 Remember, electrons are transferred up the table only. Ways to Study Metabolism • Labeling – Nitrogen, Carbon, Sulfur • Perturbing the System – Disease states • Systems Based – Genome, transcriptome, proteome, metabolome Labeling Perturbing the system 1. Natural mutations 2. Inhibitors 3. Genetic manipulation Systems Biology Microarray analysis allows who genome analysis Studying the proteome