Lecture #2Date ______ Chapter 8~ An Introduction to Metabolism
Things you must know The role of ATP in energy coupling That enzymes work by lowering the energy of activation The catalytic cycle of an enzyme that results in the production of a final product The factors that influence the efficiency of enzymes
Metabolism/Bioenergetics Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell 2 pathways Catabolic pathways: releasing energy by breaking down complex molecules (ex. Digestive enzymes breaking down food) Anabolic pathways: consuming energy to build complex molecules (ex. Amino acids linking together to form muscle protein)
Thermodynamics Energy (E)~ capacity to do work; Kinetic energy (KE)~ energy of motion Potential energy (PE)~ stored energy (when not moving) Thermodynamics~ study of E transformations 1st Law: conservation of energy: energy can transform but neither created or destroyed 2nd Law: transformations increase entropy (disorder, randomness) THIS MEANS: quantity of E is constant, quality is not
Free energy Free energy: portion of system’s E that can perform work (at a constant temperature) Exergonic reaction: net release of free E to surroundings Endergonic reaction: absorbs free E from surroundings
Energy Coupling & ATP Key to how cells work is energy coupling (using process to release energy (excergonic) to “power” and endergonic reaction) ATP (adenosine triphosphate) is composed of andenosine and 3 phosphate groups) Hydrolyze a phosphate off to release energy (now ADP)
Enzymes Enzymes are catalytic proteins: substance that can change the reate of a reaction without being altered. Activation energy is the amount of energy required to “power” a reaction Enzymes lower the activation energy…and speeds up the reaction. Active site: pocket or groove on enzyme that binds to substrate Induced fit model
How Enzymes Work Active site: pocket or groove on enzyme that binds to substrate When put together, it creates a enzyme-substrate complex The substrate is then converted into products The enzyme can be reused over and over again until no substrate left
Effects on Enzyme Activity Temperature and pH Cofactors: inorganic, nonprotein helpers; ex.: zinc, iron, copper Coenzymes: organic helpers; ex.: vitamins Competitive Inhibitors: molecules that compete for active site Noncompetitive Inhibitors: bind to enzyme and alters shape causing enzyme to not function properly
Enzyme Inhibitors Irreversible (covalent); reversible (weak bonds) Competitive: competes for active site (reversible); mimics the substrate Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation (shape); poisons, antibiotics