BIOL 111 301 1st Edition Lecture 8 Outline of Last Lecture I Metabolism II III IV V Measuring energy Thermodynamics Spontaneous Reactions Gibbs Free Energy Outline of Current Lecture I Enzymes II Measuring enzyme activity III Rates of reactions IV Inhibitors V Allosteric Regulation Current Lecture Enzymes catalytic proteins not consumed in reaction o Active site Have precise physical shape for specific reactants substrates Site of catalysis provides microenvironment Changes shape to form induced fit Applies force to break bonds form new bonds Measuring enzyme activity o How did you measure the rate of reaction in lab o Spectrophotometer Measures either transmitted or absorbed light How molecules absorb light o Enzymes alter molecules thus alter light absorbing properties Rates of Reaction Vary o Enzyme concentration o Substrate concentration o Temperature o pH Rates of Reaction Vary o Cofactors nonprotein molecules aid enzyme catalysis Inorganic metal ions Organic coenzymes from vitamins o Inhibitors o Allosteric Regulation Inhibitors o Chemicals that inactivate enzyme activity o Competitive bind active site o Non competitive bind other site but alters active site Allosteric Regulation o Examples Hemoglobin 4 polypeptides each bind O2 or CO2 cooperative binding of O2 or CO2 o Reversible binding loses affinity o Binding of molecule to protein at one site that affects protein function at another site Examples ADP catabolic enzyme activator ATP catabolic enzyme inhibitor ATP adenosine triphosphate o Function hydrolysis of ATP provides cell w energy How does ATP work in the cell o 1 Coupled exergonic and endergonic reactions to create overall exergonic G o 2 Transfer one phosphate group from ATP to reactant o 3 When phosphate group is displaced work can occur Redox Reactions o Oxidation systematic removal of electrons or loss of electrons o Reduction addition of electrons reduces overall charge o Electronegativity attraction of an atom for the electrons of a covalent bond
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