Energy & Enzymes December 9, 2018

Objectives December 9, 2018

Vocabulary Metabolism Catabolism Anabolism The totality of an organism’s chemical processes, consisting of catabolic and anabolic pathways Catabolism Release of energy by breaking down complex molecules into simpler molecules. Anabolism Involves putting things together or synthesizing complex substances from simpler substances December 9, 2018

Enzymes Enzymes are responsible for lowering the activation energy Enzymes are responsible for speeding up chemical reactions in the body Chemical Reactions Reactants When using enzymes, the reactants are called substrates Products December 9, 2018

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Amino Acids & Enantiomers December 9, 2018

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Monomers vs. Polymers Monomers are the precursors to polymers A polymer CANNOT be made without monomers Question? What is the process used to join multiple monomers together so that a polymer is produced? Polymerization In order to make proteins (enzymes) multiple amino acids must be joined together Hence, that means that the amino acid is the monomer. Amino Acid-->peptide-->polypeptide-->protein December 9, 2018

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Enzymes Structure of Enzymes Protein molecules Some enzymes are known to contain non-protein components These are known as coenzymes Vitamins frequently function as coenzymes Enzymes are very specific Substrate Maltose—Maltase Amylose—Amylase Lipid—Lipase December 9, 2018

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Exergonic Reaction December 9, 2018

Activation Energy The difference in energy between the energy for the reactants and the transition state. ALL chemical reactions must overcome the transition state. The transition state represents a hump in the road. December 9, 2018

Exergonic Reaction December 9, 2018

Exergonic Reaction A reaction that occurs spontaneously The product of an exergonic reaction has a lower energy level than that of the reactants December 9, 2018

Activation Energy Activation Energy Transition State The energy difference between reactants and the transition state Determines how rapidly the reaction occurs at a given temperature The lower the activation energy, the faster the reaction will occur The higher the activation energy, the slower the reaction will occur Transition State Represents the highest-energy structure involved in the process of a chemical reaction A chemical reaction must have enough energy to overcome the “transition state.” December 9, 2018

Enzymes Active sites Specific site on the enzyme where the substrate attaches Pocket; Lock December 9, 2018

How do Enzymes Work? Catalytic Cycle Four Steps Enzyme and substrate are available Substrate binds to enzyme (enzyme-substrate complex) Substrate is converted to products Products are released December 9, 2018

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Influences on Enzymes Temperature Extreme cold can slow enzyme action nearly to a halt As temperature rises, enzymes begin to operate more and more rapidly Extreme heat can halt enzyme action by changing the enzyme’s shape—denaturation December 9, 2018

Influences II Concentrations of Enzyme to Substrate If the concentration of an enzyme is constant, increasing the substrate concentration from zero will result in a steady rise in the reaction rate until there are equal amounts of substrate and enzyme Rate of product production increase, but eventually it will level off. December 9, 2018

Influences III Cell Acidity (pH) Most enzymes appear to work best at a pH of 7 Remember the approximate pH of blood? Rates will decrease with more acidity or alkalinity December 9, 2018

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Enzymes--Inhibitors Enzyme Inhibitors Non Competitive Inhibitors Resemble the substrate molecule for that specific enzyme Competes for the active site Reduces the productivity of enzymes by blocking Non Competitive Inhibitors Do not directly bond to the active site of the enzyme Binds at another location and alters the confirmation of the enzyme so that the active site is no longer fully functional December 9, 2018

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Control of Metabolism Depends on allosteric regulation Changes an enzymes shape and function by binding to an allosteric site Specific receptor site on some part of the enzyme molecule remote from the active site Allosteric inhibitor, binds at the allosteric site, and stabilizes the inactive form of the enzyme Makes the enzyme non-functional Activator, also binds at the allosteric site, and stabilizes the active form on the enzyme Makes the enzyme functional ATP and ADP are examples December 9, 2018

Allosteric Regulation Active Form Activator binds at the allosteric site Enzyme becomes active Substrate is able to bind at active site and the chemical reactions (conversion to products) can take place Inactive form Inhibitor binds at the allosteric site Enzyme changes shape Enzyme becomes inactive Substrate is unable to bind at the active site December 9, 2018

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Control of Metabolism II Feedback Inhibition The switching off a metabolic pathway by it’s end product The end product switches off the metabolic pathway Example of Baking a cake December 9, 2018

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Start point Theronine End Point Isoleucine If the body has enough isoleucine, isoleucine will bind at the allosteric site of the last enzyme Isoleucine, when binding at the allosteric site will behave as an allosteric inhibitor This turns the enzyme off The pathway turned off If the body uses all of the isoleucine, then isoleucine leaves the last enzyme and an allosteric activator binds and turns the enzyme on When the enzyme is turned on, the pathway is turned on December 9, 2018

Cooperativity Amplifies the response of enzymes to substrates The binding of one substrate molecule to the active site of one subunit causes all the subunits to assume their active form December 9, 2018