Biol 1411 1st Edition Lecture 11 Outline of Last Lecture I. Energy Requirements of CellII. ATPIII. EnzymesOutline of Current Lecture I. Enzymatic inhibitionII. BioenergeticsCurrent LectureInhibitors- naturally occurring and man-made molecule that bind to the enzyme and slow the reaction rates- Competitive inhibitors- compete with the natural substrate for binding site- Noncompetitive inhibitors- bind to the enzyme at a different site and alter active site, often function as metabolic regulators- Reversible inhibitor- bonds non covalently to the enzyme- Irreversible inhibitor- covalently bond to enzyme, permanently inactiveAllosteric Regulation: a type of noncompetitive regulation- Some enzymes exists in more than one shapeo Active form- can bind substrateo Inactive form- cannot bind substrate- Most allosteric enzymes are proteins with quaternary structureo Catalytic subunit with active siteo Regulatory subunits to which a small molecule can mindo Effectors can inhibit or activate an enzyme- Allosteric enzymes are important in regulating metabolic pathwayso Are very sensitive to small changes in concentration or noncompetitive inhibitors- Metabolic pathway navigationo The first reaction is the commitment step-other reactions then happen in sequenceo When enough of the end-product is present, the whole pathway will be turned offThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Feedback inhibition: the final product acts as a noncompetitive inhibitor of the first enzyme- Physical environment can also affect enzyme activityo pH Every enzyme is most active at a particular pH pH influences the ionization of functional groupso Temperature Every enzyme has an optimal temperature At high temps, non-covalent bonds begin to break Enzyme can lose its tertiary structure and become denaturedBioenergetics- Fuels- carbon-based molecules whose stored energy can be released for use- Energy is released through oxidation reactions that breakdown the fuel molecules into simpler molecules, such as CO2- Glucose- most common fuel in organisms- Metabolic pathwayso Each reaction is catalyzed by a specific enzymeo Metabolic pathways are similar in all organismso In eukaryotes, metabolic pathways are compartmentalized in organelleso Each pathway is regulated by key enzymes- usually by allosteric mechanisms- 3 metabolic pathways are involved in harvesting energy of glucoseo Glycolysis- glucose is converted to pyruvateo Cellular respiration- aerobic and converts pyruvates into water and CO2, leads to syntheses of much ATPo Fermentation-anaerobic and converts pyruvates into lactic acid or ethanol+ CO2, produces a little ATP- Glycolysis- most ancient process- Re-dox Reactionso Reduction: gain of electronso Oxidation: lose electronso Hydrogen atoms can also be involved in redox reactionso Are always coupled- Glucose is oxidized and oxygen becomes reduced- All of the e- in glucose are transferred to molecules of oxygen to form water- Glucose oxidation occurs in a series of controlled steps- Catalyzed by enzymes- Coenzyme NAD+ is a key electron carrier in redox reactionso NAD+ (oxidized_: receives e0 from glucoseo NADH (reduced): carries e- from glucose to other molecules in the mitochondria, ultimately on to O2- 5 energy-producing processes (3 pathways)o Cellular respiration Glycolysis Pyruvate oxidation Citric acid cycle Electron transport/ATP synthesis CO2 and H2Oo Fermentation Glycolysis Fermentation Lactate or alcohol- Glycolysiso Inputs: Glucose, 2 NAD+, 2ADP + 2Pio Outputs: 2 molecules of pyruvate, 2 NADH, 2ATP(net)o 10 enzyme-catalyzed reactions 1-5 energy investment 6-10 energy
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