Concept 8.1 What is energy? Potential energy = stored energy Chemical bonds Concentration gradients (can be used to do cellular work) Electrical potential Kinetic energy = movement energy Heat = molecular motion Mechanical = moving molecules past each other Electrical = moving charged particles Forms of energy Biker at top of hill potential Biker going down hill kinetic Why do cells need energy? Synthetic work = building macromolecules (e.g., making protein) mechanical work = moving molecules past each other e.g., muscle shortening concentration work = creating chemical gradients e.g. storing glucose electrical work = creating ion gradients e.g., unequal distribution of sodium and potassium ions Metabolic pathways Catabolic pathways ? release energy