BIOL 1441 1st Edition Lecture 15 Outline of Last Lecture I Exergonic Reactions II Endergonic Reactions III Equilibrium and Metabolism IV Energy Coupling a ATP V Enzymes Regulate Metabolism Outline of Current Lecture I Allosteric Regulation of Enzymes II Cooperativity III Feedback inhibition IV Photosynthesis respiration V Cellular respiration VI Redox reactions VII Antioxidants VIII Relocation of electrons IX Electron transport chain Current Lecture I Allosteric Regulation of Enzymes These 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 II III IV V a Any case where a protein s function at one site is affected by binding of a regulatory molecule at another site i NOT AT ACTIVE SITE b May either inhibit or stimulate an enzyme s activity c Most allosterically regulated enzymes made from polypeptide subunits i Each having own active site d Entire complex oscillates between 2 shapes i Active inactive forms e Binding of activator stabilizes active form f Binding of inhibitor stabilizes inactive form Cooperativity a Form of allosteric regulation that can amplify enzyme activity b Substrate binding to 1 active site stabilizes favorable conformational changes at all other subunits Feedback Inhibition a End product shuts down the pathway b Stops enzyme at the beginning to stop the whole process c Prevents cell from wasting chemical resources by synthesizing more product than needed d Negative feedback variables moving in opposite ways i Ex Getting a fever and medicine bringing it back to 98 6 moving opposite e Positive feedback moving in same direction i Ex Getting a fever and just keep getting hotter in same direction Photosynthesis Respiration a Ps photosynthesis b Rs respiration c Photosynthesis plants convert sunlight into chemical energy store in organic molecules endergonic d Respiration breaking down organic molecules exergonic generates ATP i In humans aerobic with oxygen ii Without oxygen anaerobic goes through fermentation not citric acid cycle e Glycolysis fermentation happens in cytosol Cellular Respiration a Can break down carbs fats proteins for fuel stick with glucose for simplicity b Breaking down glucose exergonic rxn c DG 686 kcal mol spontaneous i Neg releasing energy from rxn ii Pos required that amount of energy for the rxn d Transfer of electrons relocation electrons releases stored energy in organic molecules e Released energy is used to synthesize ATP VI VII VIII Redox Reactions a Transfer of electrons from one reactant to another oxidation reduction rxn s redox rxn s i Oxidation lose an electron ii Reduction gain an electron reducing the positive charge of the atom b c electrons are negative iii Electron donor reducing agent X gets oxidized iv Electron acceptor oxidizing agent Y gets reduced v Redox rxn s always coupled requires both Antioxidants a glutathione vitamin C vitamin E b catalase superoxide dismutase peroxidases c STOPS OXIDATION LOSING ELECTRONS i KEEPS MOLECULES FROM STEALING ELECTRONS BY DONATING ELECTRONS Relocation of Electrons a Electron loses potential energy when it shifts from a less electronegative atom toward a more electronegative one i From H O OR from C O ii Releases energy exergonic spontaneous 1 H O or C O 2 STABILITY WHICH ATOM HOLDS ONTO ELECTRON MORE TIGHTLY b Losing potential energy like water flowing down a hill i Moving from high energy to low ii Unstable to stable 1 Easy to pull electron from hydrogen unstable higher energy state 2 Once bound to oxygen very electronegative very hard to pull electron away very stable lower energy state c Organic molecules with an abundance of H atoms excellent fuels d H bonds source of hilltop electrons GOING FROM HIGH LOW e Energy released as fall down energy gradient when they are transferred to oxygen i Unstable Stable ii High energy Low energy iii Less electronegative more electronegative f Main energy foods carbs fats reservoirs of electrons associated with hydrogen g Rxn s use H atoms to transfer electrons i Hydrogen atom 1 proton 1 electron ii Proton hydrogen ion H stripped of its electron h Electrons 1st transferred to NAD coenzyme i Nicotinamide adenine dinucleotide IX ii Derivative of niacin B vitamin iii Oxidizing agent it gets reduced gains an electron i NAD reduced NADH i NAD IS IN THE OXIDIZED STATE because it hasn t picked up the electron yet j Dehydrogenase enzyme that removes 2 hydrogen atoms from glucose oxidizing glucose k Delivers 2 electrons and 1 proton to NAD the other proton is released CREATES NADH H l NAD OXIDIZED m NADH REDUCED n Bottom of electro chain most electronegativity o Every time electron is transferred only small amounts of energy lost p Work the free energy does creates a concentration gradient q Oxygen is the final acceptor of chain binds to hydrogen and forms water and leaves Electron Transport Chain a Electron transport chain release energy in steps instead of one big rxn b Chain many molecules mostly proteins embedded into the mitochondrial membrane c Remove electrons from food shuttled by NADH to top of the chain like top of a hill high energy d Bottom lower energy end oxygen captures electrons along with H forming water e Electron transfer from NADH to oxygen exergonic rxn i 53 kcal mol f Electrons cascade down the chain from 1 carrier to the next releasing small amounts of energy with each step until reaches oxygen g Each downhill carrier is more electronegative than the one before h Oxygen terminal electron acceptor i Great affinity for electrons i Moving from unstable to very stable releasing energy j Food NADH electron transport chain oxygen k Basic mechanisms of cellular respiration l Actually has 3 metabolic stages i Glycolysis ii Citric Acid Cycle Kreb s cycle iii Oxidative Phosphorylation m Glycolysis i Breakdown glucose glucose into pyruvate 1 1 glucose 2 pyruvate molecules ii oxidizing glucose partial oxidation n citric acid cycle i oxidizes pyruvate