Chapter 15 Design of metabolism

G, Free Energy, recall:

For biochemical reactions, we define a different standard state for the concentration of H+ standard state for [H+] = 10-7 M, pH = 7.0 this modified standard state is given the symbol G°’

ATP the experimental value of K’eq = 2.23 x 105

ATP-Why? repulsion resonance BUT,it’s kinetically stable

Other “high energy compounds

"High energy" substance: a thermodynamically unstable substance whose hydrolysis or decomposition can be easily coupled to an unfavorable reaction. The arbitrary cut-off is ~-10kJ/mol. There is no such thing as a "high energy bond" per se.

Coupled Reactions Free energies are additive; favorable rxns can drive unfavorable;e.g.sequential coupling

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Sequential coupling

Simultaneous coupling Example:Glucose to glucose-6-phosphate

Example: calculate G°’ for this reaction involving phosphoenolpyruvate (PEP) and decide whether or not it is spontaneous use the following information from Table 14.1

Under aerobic conditions, glucose is oxidized to carbon dioxide and water the efficiency of the energy conservation under aerobic conditions is approximately 34% Metabolism concerns how you get from here to there!!

Metabolic strategies-Oxidation(burning of carbon containing compounds)

Substrate level phosphorylations

Ion gradients

Overall Process

Recurring Motifs in Metabolism “Activated” electron and functional group carriers

Electron Carriers: NAD+

Electron Carriers: FAD

Typical Oxidation Reactions

“Carbon” carriers

Chemical Reaction “themes” in metabolism

Chemical Reaction “themes” in metabolism: Patterns

Factors Affecting Metabolic Rate Metabolism operates at a steady state. Metabolites flow through the steady state

Factors Affecting Metabolic Rate

Factors Affecting Metabolic Rate Metabolites flow through the steady state ATP

Factors Affecting Metabolic Rate

Factors Affecting Metabolic Rate

Factors Affecting Metabolic Flow or flux through pathways Amounts of enzymes Catalytic activity of enzymes Availability of substrates

ATP Balance affects many metabolic pathways

ATP Balance affects many metabolic pathways

CONTROL OF METABOLIC FLUX, J rate determining step S A B J P e.g. glucose pyruvate

CONTROL OF METABOLIC FLUX, J e.g. Substrate Cycling: See glycolysis (F-6-P to F1,6-BP)