Cellular Energy and Metabolism

Metabolism/Bioenergetics Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell Catabolic pathways: degradative process such as cellular respiration releases energy Anabolic pathways: building process such as protein synthesis; photosynthesis consumes energy

Types of NRG Energy (E) = capacity to do work Kinetic energy~ energy of motion Potential energy~ stored energy

Thermodynamics Thermodynamics = study of E transformations 1st Law: conservation of energy; E transferred/transformed, not created/destroyed 2nd Law: transformations increase entropy (disorder, randomness) Combo: quantity of E is constant, quality is not

Free energy Free energy (G) = portion of system’s E that can perform work at constant temp. and pressure ΔG = ΔH –TΔS Δ = change in H = enthalpy (total E of system) S = entropy (disorder) T = absolute temperature (Kelvin) If ΔG < 0, the reaction will occur spontaneously If ΔG > 0, the reaction will not occur spontaneously

Moving Toward Equilibrium

Exergonic vs. Endergonic Exergonic reaction: net release of free E to surroundings ΔG < 0 (spontaneous) Endergonic reaction: absorbs free E from surroundings ΔG > 0 (not spontaneous)

Adenosine Triphosphate ATP tail: high negative charge, high repulsion ATP hydrolysis is exergonic Releases 7.3 kcal of E per mole of ATP

Energy coupling: use of exergonic process (ATP hydrolysis) to drive an endergonic one

Energy Coupling Phosphorylation ATP hydrolysis creates E Enzymes transfer P to a reactant Creates a phosphorylated Intermediate (less stable) Reaction occurs spontaneously