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Spontaneous chemical reactions occur without a need for outside energy but may be very slow Free energy: ΔG Catalyst: a chemical agent that speeds up a reaction without being consumed by the reaction Enzyme: a catalytic protein AB + CD AC + BD (SPONTANEOUS EXERGONIC) Every chemical reaction between molecules involves bond breaking and bond forming Free energy of activation, or activation energy (EA): initial investment of energy to start the reaction Transition state: the summit where the reactants are in an unstable condition Enzymes are proteins which are biological catalysts Speed up reactions by lowering the EA barrier Heat denatures proteins and kills cells and it would speed up ALL reactions, so organisms need alternative- catalysis Enzymes catalyze reactions by lowering the EA barrier, Enabling the reactant molecules to absorb enough energy to reach the transition state Substrate: the reactant an enzyme acts on Enzyme-substrate complex: formed by an enzyme binding to its substrate Enzymes + Substrate(s) Enzyme-substrate complex Enzyme + Product(s) Enzymes=proteins=macromolecules Active site: the restricted region of the enzyme molecule that binds to the substrate a pocket on the surface of the protein Induced fit: when the enzyme changes shape slightly so that the active site fits more snugly around the substance Brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction In most enzymatic reactions, substrate binds to active site and is held there by weak interactions Side chains (R groups) of a few of the amino acids that make up the active site catalyze the conversion of substrate to product Product departs Repeats Most metabolic reactions are reversible and an enzyme can catalyze both forwards and backwards The active site can lower an EA barrier by orienting substrates correctly, straining their bonds, providing a favorable microenvironment, and covalently bonding with a substrate Each enzyme has an optimal temperature and pH (6-8) Cofactors: nonprotein helpers for catalytic activity required by many enzymes coenzyme: if the cofactor is an organic molecule http://www.youtube.com/watch?v=5eBzLgleVL8 Inhibitors reduce enzyme function If done by covalent bonds the effects are irreversible. Most are weaker bonds making them reversible Competitive inhibitor: binds to active site, reduces productivity of enzymes by blocking substrates from entering active sites - can be overcome increase [ ] of the substrate Noncompetitive inhibitor: impede reactions by binding to different site on enzyme Allosteric regulation: any case where a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site - results in either inhibition or stimulation of activity Cooperativity: mechanism that amplifies the response of enzymes to substrates Feedback inhibition: a metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway Ex: thermostat Some enzymes are grouped into complexes Some are transported into membranes Others are contained inside organelles Metabolism (intersecting set of chemical pathways characteristic of life)= choreographed interplay of thousands of different kinds of cellular molecules http://www.youtube.com/watch?v=2N-ydg4J4tA http://www.youtube.com/watch?v=M5bftq-W2aY http://www.uic.edu/classes/bios/bios100/lec turesf04am/lect04.htm http://www.youtube.com/watch?v=5eBzLgle VL8 http://www.youtube.com/watch?v=2Nydg4J4tA http://courses.washington.edu/conj/protein/ proregulate.htm http://bio1152.nicerweb.com/Locked/media/ ch08/