Chapter 7 Enzymes and Energetics Outline 1 Energy Laws of Thermodynamics Free energy G G H T S 2 3 4 5 Exergonic reactions and Endergonic reactions ATP Redox reactions Enzymes Energy flow within and among organisms all living are going to depend on light energy from the sun only certain plants and algae will be able to go through photosynthesis in cellular respiration energy stored in the chemical bonds of glucose is going to be re leased and used in chemical activities of life ex homeostasis a b metabolism all chemical reactions taking place in an organism two types of reactions anabolism synthesis needs an input of energy to make bonds catabolism hydrolysis degradation There are two basic types of Energy kinetic energy of motion potential energy of state or position it includes stored energy in chemical bonds types of cell work 1 2 3 mechanical ex movement of chromosomes in the cell transport chemical how the cell controls exergonic and endergonic reactions supply of cellular energy 1 2 3 metabolism going to come from catabolism potential energy kinetic energy The first law of thermodynamics energy is neither created or destroyed 1st law of thermodynamics energy is neither created or destroyed 2nd law of thermodynamics disorder tends to increase energy conversion is inefficient Entropy S is a measure of disorder in the system the more disorder the less energy there is to do work Not all energy can be used free energy G is available to do cell work Enthalpy H free energy G Temperature entropy S in a chemical reaction Free Energy G G H T S Exergonic and Endergonic Reactions complex molecules small molecules free energy hydrolysis or degradation releases energy exergonic catabolism G negative number Exergonic and Endergonic Reactions Free energy small molecules complex molecules requires energy endergonic anabolism G positive number exergonic and endergonic reactions are coupled ATP adenosine triphosphate nucleotide adenine ribose and 3 phosphate groups the cell uses energy that is temporarily stored in ATP ATP ADP ratio 10 ATP for 1 ADP Adenosine diphosphate How phosphate group transferred phosphorylation released as Pi cell is going to transfer energy through 3 mechanisms ATP in the form of electrons and in the form of protons Redox Reactions Slide Electrons transfer energy transfer 1 2 3 oxidation a substance loses electrons means its giving up energy reduction a substance that gains electrons meaning that it receives energy redox reactions is another way a cell moves energy from one compound to another they are highly important in cellular respiration and photosynthesis Electron Carriers Transfer Hydrogen Atoms movement of H atom electron acceptor molecules an electron is transferred to an acceptor molecule nicotinamide adenine and dinucleotide NAD which is reduced to NADH XH2 NADH X NADH H Reduced Form store free energy enzymes biological catalysts that increase the speed of a chemical reaction without be Enzymes proteins RNA molecules Energy of activation E A energy is required to break existing bonds and begin the re Enzymes lower the energy of activation of the chemical reaction Important Classes of Enzymes enzymes are substrate specific they act on 1 or few substances Enzymes Slide ing consumed action Enzyme Substrate Complex globular protein clefts grooves active sites region of the E to which the substrate S binds to form enzyme substrate induced fit binding of the substrate to the enzyme that causes a change in the shape of complex the enzyme produces a perfect fit Enzyme Activity 1 the activity of an enzyme is influenced by cofactors apoenzyme cofactor coenzyme organic cofactor ex of coenzymes NADH ATP 2 3 4 temperature ph inhibitors Effects of Temperature on Enzyme Activity optimal temperature the rate of reaction is fastest highest temperature irreversibly denature most enzymes Effects of pH on Enzyme Activity PH for most human enzymes if 6 to 8 Exceptions Pepsin stomach optimal pH 2 Trypsin small intestine optimal pH 8 Feedback Inhibition the chemistry of life is organized into metabolic pathways series of metabolic steps one enzyme catalyzes each step feedback inhibition the formation of a product inhibits an earlier reaction in the sequence Reversible Inhibition an inhibitor forms weak chemical bonds with the enzyme can be competitive or noncompetitive Enzyme Inhibition 1 2 competitive inhibition 3 noncompetitive inhibition inhibitor binds at a site other than the active site Irreversible inhibition inhibitor permanently inactivates an enzyme ex Heavy metals such as mercury and lead nerve gases cyanide Noncompetitive Inhibition An Allosteric Enzyme allosteric site different from active site inhibitor competes with normal substrate for binding to the active site of the enzyme