BIOL 1441 1st Edition Lecture 15 Outline of Last Lecture I. Exergonic ReactionsII. Endergonic ReactionsIII. Equilibrium and MetabolismIV. Energy Couplinga. ATPV. Enzymes Regulate MetabolismOutline of Current Lecture I. Allosteric Regulation of EnzymesII. Cooperativity III. Feedback inhibition IV. Photosynthesis/respirationV. Cellular respirationVI. Redox reactionsVII. AntioxidantsVIII. Relocation of electronsIX. Electron transport chainCurrent LectureI. Allosteric Regulation of EnzymesThese 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.a. Any case where a protein’s function at one site is affected by binding of a regulatory molecule at another sitei. NOT AT ACTIVE SITEb. May either inhibit or stimulate an enzyme’s activityc. Most allosterically regulated enzymes made from polypeptide subunitsi. Each having own active sited. Entire complex oscillates between 2 shapesi. Active & inactive formse. Binding of activator stabilizes active formf. Binding of inhibitor stabilizes inactive formII. Cooperativitya. Form of allosteric regulation that can amplify enzyme activityb. Substrate binding to 1 active site stabilizes favorable conformational changes at all other subunits III. Feedback Inhibitiona. End product shuts down the pathwayb. Stops enzyme at the beginning to stop the whole processc. Prevents cell from wasting chemical resources by synthesizing more product thanneededd. Negative feedback: variables moving in opposite waysi. Ex. Getting a fever, and medicine bringing it back to 98.6 (moving opposite)e. Positive feedback: moving in same directioni. Ex. Getting a fever and just keep getting hotter (in same direction)IV. Photosynthesis & Respirationa. Ps- photosynthesisb. Rs- respirationc. 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 cyclee. Glycolysis/fermentation happens in cytosolV. Cellular Respirationa. Can break down carbs, fats, proteins for fuel- stick with glucose for simplicityb. Breaking down glucose- exergonic rxnc. DG = -686 kcal/mol (spontaneous)i. Neg (-) releasing energy from rxnii. Pos (+) required that amount of energy for the rxnd. Transfer of electrons- relocation electrons releases stored energy in organic moleculese. Released energy is used to synthesize ATPVI. Redox Reactionsa. Transfer of electrons from one reactant to another- oxidation-reduction rxn’s (redox rxn’s)i. Oxidation- lose an electronii. Reduction- gain an electron (reducing the positive charge of the atom b/c electrons are negative)iii. Electron donor- reducing agent (X) gets oxidizediv. Electron acceptor- oxidizing agent (Y) gets reducedv. Redox rxn’s always coupled- requires bothVII. Antioxidantsa. glutathione, vitamin C, vitamin E b. catalase, superoxide dismutase, peroxidasesc. STOPS OXIDATION- LOSING ELECTRONSi. KEEPS MOLECULES FROM STEALING ELECTRONS BY DONATING ELECTRONSVIII. Relocation of Electronsa. Electron loses potential energy when it shifts from a less electronegative atom toward a more electronegative onei. From H ® O OR from C ® Oii. Releases energy (exergonic, spontaneous)1. HO or CO2. STABILITY: WHICH ATOM HOLDS ONTO ELECTRON MORE TIGHTLYb. Losing potential energy like water flowing down a hilli. Moving from high energy to low ii. Unstable to stable1. Easy to pull electron from hydrogen- unstable, higher energy state2. Once bound to oxygen (very electronegative), very hard to pull electron away- very stable, lower energy statec. 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 oxygeni. Unstable ® Stableii. High energy ® Low energyiii. Less electronegative ® more electronegativef. Main energy foods- carbs & fats- reservoirs of electrons associated with hydrogeng. Rxn’s use H atoms to transfer electronsi. Hydrogen atom- 1 proton + 1 electronii. Proton- hydrogen ion (H+), stripped of its electronh. Electrons 1st transferred to NAD+ (coenzyme)i. Nicotinamide adenine dinucleotideii. Derivative of niacin- B vitaminiii. Oxidizing agent- it gets reduced (gains an electron)i. NAD+ reduced® NADHi. NAD + IS IN THE OXIDIZED STATE: because it hasn’t picked up the electron yetj. 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+ = OXIDIZEDm. NADH = REDUCEDn. Bottom of electro chain=most electronegativityo. Every time electron is transferred=only small amounts of energy lostp. Work the free energy does creates a concentration gradientq. Oxygen is the final acceptor of chain-binds to hydrogen and forms water and leavesIX. Electron Transport Chaina. Electron transport chain- release energy in steps instead of one big rxnb. Chain- many molecules, mostly proteins embedded into the mitochondrial membranec. 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 watere. Electron transfer from NADH to oxygen exergonic rxn i. -53 kcal/molf. Electrons cascade down the chain from 1 carrier to the next- releasing small amounts of energy with each step until reaches oxygeng. Each downhill carrier is more electronegative than the one before h. Oxygen- terminal electron acceptori. Great affinity for electrons!i. Moving from unstable to very stable- releasing energyj. Food ® NADH ® electron transport chain ® oxygenk. Basic mechanisms of cellular respirationl. Actually has 3 metabolic stagesi. Glycolysisii. Citric Acid Cycle (Kreb’s cycle)iii. Oxidative Phosphorylationm. Glycolysis:i. Breakdown glucose glucose into pyruvate1. 1 glucose= 2 pyruvate moleculesii. oxidizing glucose=partial oxidationn. citric acid cycle:i. oxidizes