BIOL 111 301 1st Edition Lecture 8Outline of Last Lecture I. MetabolismII. Measuring energyIII. ThermodynamicsIV. Spontaneous ReactionsV. Gibbs Free EnergyOutline of Current LectureI. Enzymes II. Measuring enzyme activityIII. Rates of reactionsIV. Inhibitors V. Allosteric Regulation Current Lecture- Enzymes-catalytic proteins, not consumed in reactiono 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 activityo How did you measure the rate of reaction in lab?o Spectrophotometer Measures?-either transmitted or absorbed light How?-molecules absorb lighto Enzymes alter molecules thus alter light absorbing properties.- Rates of Reaction Varyo Enzyme concentrationo Substrate concentrationo Temperatureo pH- Rates of Reaction Varyo Cofactors: nonprotein molecules aid enzyme catalysis Inorganic: metal ions Organic: coenzymes, from vitaminso Inhibitorso Allosteric Regulation- Inhibitorso Chemicals that inactivate enzyme activityo Competitive: bind active siteo Non-competitive: bind other site, but alters active site- Allosteric Regulationo Examples: Hemoglobin 4 polypeptides each bind O2 or CO2 cooperative binding of O2 or CO2 o Reversible binding, loses affinityo 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 triphosphateo 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 (-ΔG).o 2. Transfer one phosphate group from ATP to reactant.o 3. When phosphate group is displaced, work can occur.- Redox Reactionso Oxidation: systematic removal of electrons or loss of electronso Reduction: addition of electrons (reduces overall charge)o Electronegativity: attraction of an atom for the electrons of a covalent
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