Metabolism: Energy and Enzymes

Energy  Ability to do work, change matter  Kinetic – energy in motion  Potential – stored energy Chemical energy (food) Mechanical energy (motion)

Thermodynamics  2 Laws: 1. Law of conservation of energy – Energy cannot be created or destroyed, but it can be changed from one form to another (heat energy) 2. Energy cannot be changed from one form to another without a loss of usable energy.  When heat is released, it is not longer available to do work, lost to the environment. Cells are 40% efficient, rest of energy is given off as heat

Entropy  Used to indicate the relative amount of disorganization in universe  Every process that occurs in cells increases the total entropy of the universe.  More organized = less stable Clean room, more organized but less stable than a messy room entropy clip

Metabolic reactions  Metabolism  Reactants – products  Free energy – amount of available energy to do work after a chemical reaction has taken place (G)  Exergonic reactions – delta G is negative, products have less energy than the reactants, reaction is spontaneous, energy is released, ex. ATP breakdown  Endergonic reactions – delta G is positive and products have more free energy than the reactants. Can only take place if there is an input of energy.

Adenosine Triphosphate  Energy currency, universal, can be used in many different types of reactions.  Composed of Adenine (nitrogen base), ribose sugar and 3 phosphate groups  Uses of ATP Chemical work – synthesize macromolecules Transport work – pumps Mechanical work – muscle contraction, cilia to beat, chromosomes to move.

Coupling reactions  Energy released by exergonic reactions drive endergonic reactions.  ATP breakdown is exergonic

Function of ATP  Chemical work – helps to synthesize macromolecules  Transport work – supplies energy for pumps across membrane  Mechanical work – supplies energy to do work, muscle contraction, cilia beat…