Energy from the environment food is broken down in

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Energy from the environment (food) is broken down in exergonic reactions to drive the endergonic reactions in our bodies o Ex: cell phone working require energy; energy comes from battery; inside battery there are exergonic reactions working; inside cell phone there are endergonic reactions happening; if you put the battery in the cell phone, the energy is being transferred to the cell phone Called a couple reactions because without exergonic reactions, endergonic reactions cannot happen o Equilibrium Reactions are at equilibrium when reactants are converted to products at the same rate as products are converted into reactants. Or when the rate of the forward reaction and the rate of the reverse reaction are the same Energy of products – energy of reactants = energy that is used/transferred Reactants and products have the same amount of free energy Energy change = 0 o Activation energy The energy that is required for the reactants to engage in a reaction Most molecules lack the activation energy needed for a reaction to occur Ex: ball rolling down the hill >> but how did the ball get on top the hill in the first place??? Activation energy can take the form of hear (molecules colliding together = friction) Activation energy barrier can also be surmounted through a catalysts Exergonic reaction = reactants already have more energy than the products Catalysts will help increase the amount of energy needed for the reaction to occur; this speeds the reaction up
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14 Catalysts provide a docking site for the reactants to be exposed to each other; makes them happen more quickly Catalysts don’t determine whether the reaction occurs but how fast it occurs o Enzymes A class of proteins that serve as biological catalysts . Catalysts are chemicals that Increase the rate of reaction Are not changed by the reaction (so can be used repeatedly) Have no effect on free energy of reactants or products In enzymatic reactions, reactants are called substrates o Substrates are what enzymes bind to Catalyzed vs non-catalyzed reactions A small hill means a reaction happens faster Without a catalyst, the reaction will occur much slower Ligand-Receptor Interactions Ligand A and Ligand B are both specific for the protein o Ligand = a molecule that binds to a receptor Ligand B has a higher affinity (attraction) for the protein than Ligand A because it can make more bonds with the protein o A lock and key analogy = the right key will fit the most tight If you have enough ligands, they all get bond; but at low concentrations of ligands and they have to compete, ligand B will win Mechanism of Enzyme Activity Enzymes provide an active site where the substrate fits; get a enzyme- substrate complex where the substrate is altered; a product is then formed and the product breaks free and the enzyme will go back to its original shape; these enzymes get used up over and over again Substrate specificity
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