ENZYMES Are proteins for the most part Enable speed up reactions DO NOT CONTAIN ENERGY Enzymes do not make anything happen that could not happen on it s own Enzymes are not altered or used up in a reaction catalysts Catalysts a substance that lowers the activation energy of a reaction but is not itself consumed in the reaction Enzyme a large molecule usually protein that accelerates the rate of catalyzes a specific biochemical reaction Any reaction needs a push to get started Activation energy The energy push required to initiate a chemical reaction Lock and Key model specific shape is important for enzyme substrate interaction substrate the molecule being acted upon by the enzyme Active site the area in a groove or cleft within the globular tertiary structure of the enzyme where the substrate binds Induced Fit enzyme shape actually changes when substrate binds Enzymes Orient molecules to bring them together into a more complex molecule endergonic Orient molecules to break them apart exergonic Enzyme Regulation 1 Competitive steric inhibition occurs when a similarly shaped molecule binds to the active site Can be overcome by increasing substrate concentration 2 Non competitive inhibition an inhibitor molecule binds at a non active site and alters conformation of the enzyme Changes the shape 3 Allosteric Regulation other shape substrate is broken into products product binds to enzyme at different site and causes the active site to change shape ENERGY Work the process of moving an object against a force Energy the capacity to do work Potential energy stored energy available for later use gasoline Kinetic energy movement energy in current use Laws of Thermodynamics 1 First law The total amount of energy in the universe remains constant Energy can neither be lost or gained only transformed 2 Second Law The amount of energy available to do work is constantly decreasing Reactions will run spontaneously only in a direction from higher order and energy to lower order and energy Heat is disordered energy which cannot be used by living things Entropy A measure of disorder The 2nd law states that entropy disorder will always increase However the 2nd Law applies to closed systems no energy Earth is an open system There is a constant input of energy from the sun Biological activity brings about local increases in order biological activity local increase in order less entropy biological activity generates heat more entropy For a reaction to occur spontaneously in a closed system the energy of the products must be less than the energy of the reactants That is less energy remains for work after the reaction That is the products low energy SO 2nd law favors breakdown disorder but also stipulates that complex molecules can be made as long as there is an input of energy Two kinds of reactions Endergonic energy in The free energy of the products is more than that of the reactants energy has been gained or stored reactions that store energy i e photosynthesis UPHILL Exergonic energy out The free energy of the products is less than that of the reactants reactions that release energy i e respiration DOWNHILL Free Energy is a measure of the energy available in the chemical bonds of a molecule that is available to do work ATP Adenosine triphosphate Energy currency of cell There is a tremendous amount of free energy stored in the bonds of an ATP molecule high energy bonds three negative charges energy is released when a PO4 group is cleaved Coupled reaction Both exergonic and endergonic reactions happening at the same time it takes energy to store energy The 2nd law stipulates
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