Gibbs free energy (G) Energy available to do work when temperature and pressure are uniform
ΔG < 0 (Negative) - exergonic reaction, spontaneous, releases energy.
ΔG > 0 (Positive): - endergonic reaction, non-spontaneous, requires energy.
ΔG = 0: - equilibrium, maximum stability, no work can be done.
Gibbs Equation: ΔG = ΔH - TΔSΔH (enthalpy): Change in total energy (often thought of as heat)
ΔH < 0 (negative): exothermic, releases heat
ΔH > 0 (positive): endothermic, absorbs heat
T (temperature): in kelvin (always positive)
ATP (adenosine triphosphate)
- structure: Ribose sugar, adenine nitrogenous base, three phosphate groups
- function: Energy currency of the cell
- high potential energy due to repulsion between negatively charged phosphate groups
- hydrolysis of terminal phosphate (ATP → ADP + Pi) releases energy (exergonic)
energy coupling
- cells use energy released from ATP hydrolysis (exergonic) to power endergonic reactions (synthesizing glutamine, transport work, mechanical work)
Regeneration
- ADP + Pi → ATP (endergonic, powered by catabolism, primarily in mitochondria)