Ch. 27: The Integration of Metabolism

Evolved Coupling Stoichiometry

Number of ATP molecules a pathway has evolved to produce or consume (compromise that optimizes both energy efficiency & regulation)

ATP Coupling Coefficient

Number of ATP molecules consumed or produced per mole of substrate (helps find the thermodynamic favorability of a reaction or pathway)

Solvent Capacity

Cell’s ability to keep all metabolites solvated as ATP enables reactions to occur at manageable metabolite conc, avoiding the need for high solute levels

Energy Charge

An index reflecting the cell’s energy status, calculated from the ratio of ATP, ADP, & AMP. (values range from 0 (all AMP) to 1 (all ATP))

Metabolic Steady State

State in which the conc. of metabolites remain constant over time, even though there is a continuous metabolic flux (allows for dynamic balance & adaptability in metabolism)

B-hydroxybutyrate

Ketone body derived from fatty acids that serve as an alt energy source for brain during fasting.

Adenylate Kinase

Enzyme that maintains adenine nucleotide balance by catalyzing 2ADP —> ATP + AMP, regenerating ATP & signal energy status

Creatine Kinase

Enzyme that acts as an ATP buffer in muscle, rapidly supplying energy during the initial phases of muscle contraction.

Muscle Protein Degradation

During fasting or stress, muscle proteins break down into amino acids; some convert to alanine

Alanine

transported to the liver for gluconeogenesis as a “fuel of last resort”

Leptin

Peptide hormone secreted by adipocytes in proportion to fat stores, regulating appetite by decreasing food intake & promoting energy expenditure.

Acidosis

Condition where blood become too acidic resulting from ethanol metabolism (increases NADH & inhibits gluconeogenesis, causing lactic acid buildup)