Week 14: Metabolism and Enzymes & Glycolysis and Oxidative Phosphorylation
Week 14: Metabolism and Enzymes & Glycolysis and Oxidative Phosphorylation Bio 107
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This 7 page Class Notes was uploaded by Rachel Johnson on Saturday December 5, 2015. The Class Notes belongs to Bio 107 at Washington State University taught by William Davis in Summer 2015. Since its upload, it has received 15 views. For similar materials see Biology in Biology at Washington State University.
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Date Created: 12/05/15
Metabolism and Enzymes II Energy Storage in Chemical Bonds The making and breaking o bonds are what drive energy conversions Energy is based on the distance e- are from the nucleus in a bond Further away = increased PE and closer = decreased PE Bond energy increases if e- are well shared Difference in electronegativity is minimal (nonpolar bond) Gibbs Free Energy Related to two states State of product Energy within reactants ΔG = G -p r ΔG = ΔH – T Δ S H = enthalpy S = entropy T = temperature ΔG < 0 → system can do work on the surroundings Spontaneous Runs in one direction Ex: catabolic reactions ΔG > 0 → surroundings must do work on the system for a change to occur Nonspontaneous Ex: anabolic reactions Entropy = disorder of a system Increased S = increased freedom of molecules Exergonic reactions Release energy into the surroundings Spontaneous ΔG r ΔG p Keeps going to completion once started Endergonic reactions Absorb energy from surroundings Nonspontaneous ΔG r ΔG p *can understand spontaneous/nonspontaneous reactions based off of bond energies *metabolism requires both matter and energy to occur Introduction to Enzymes All reactions need an initial energy input to start (activation energy) A “barrier” that needs to be overcome Enzymes lower the activation energy needed Another way is to add heat (not the best option for living organisms) *transition state = intermediate between reactants and products Reaction pathway Active site binds to its substrates Specificity → usually only binds to a few substrates Stabilizes the transition state and lowers the activation energy Releases products *enzymes are typically unchanged and are ready to activate more substrates Metabolism and Enzymes III Enzyme Activity Tertiary structure changes upon binding (tertiary structure = 3D structure) “induced fit” Temperature and pH effects Enzymes have evolved to function at a specific narrow-range of temperature and pH possessed by the organism they inhabit Thermophilic enzymes work best at higher temperatures *at opposite and extreme temperatures and pHs, proteins denature (unfold) Competitive inhibitors Bind to the active site Compete with the substrates *slows the process down, but doesn’t shut it off Can be overcome by an increase of substrate concentration Allosteric regulation Requires a quaternary structure that can change from active to inactive and has multiple active sites Activators lock enzyme in active state Bind to an area away from the active site Increases activity Inhibitors lock enzyme in an inactive state (closes down active sites) Bind away from active site Decreases activity *enzyme fluctuates between active and inactive but locks when there is an abundant presence of activators or inhibitors Enzyme Pathways Enzymes usually work in pathways Catabolic and anabolic pathways are characterized by a series of enzyme reactions Pathway can be inhibited at any one of the enzymes in the pathway Intermediates build up from the active enzymes prior to the inhibited one *air = source of all biomass ATP (Energy Intermediate) ATP hydrolysis releases energy ATP → ADP = highly exergonic Catabolic reactions generate ATP and anabolic reactions use it *a lot of the cell’s energy goes into making and breaking ATP Glycolysis and Oxidative Phosphorylation I Redox Reactions in Biology *reduced = gain e- (oxidizing agent) *oxidized = lose e- (reducing agent) NAD = intermediate that moves e- Oxidized form = NAD + Reversibly cycle between the two forms Reduced form = NADH Overview of Carbohydrate Catabolism Glycolysis Initial input of 2 ATP Produces 4 ATP, 2 NADH, 2 pyruvate, and 2 H O 2 *no net loss of carbon Regulation Phosphofructokinase Inhibited by elevated levels of ATP Activated by AMP (ATP with only one phosphate) Allosterically regulated Pyruvate oxidation Energy conversion Produces 1 NADH Matter conversion Produces 1 CO a2d I Acetyl CoA (contains 2 carbons) Citric acid cycle Energy conversion Produces 3 NADH, 1 FADH , and21 ATP Matter conversion Produces 2 CO 2 Entry point depends on molecule Proteins start at pyruvate oxidation Lipids start at the citric acid cycle Converting fatty acids to Acetyl CoA = beta oxidation *control of metabolism is dictated by the energy needs of the cell Glycolysis and Oxidative Phosphorylation II Oxidative Phosphorylation Overview *occurs in the inner membrane of the mitochondria 2 coupled reactions Electron transport chain releases energy and builds a hydrogen gradient across the membrane which drives ATP synthase through chemiosmosis Electron transport chain (ETC) e- brought in on NADH or FADH 2 Move through 4 protein complexes (Cytochromes I, II, III, and IV) Coenzyme Q 10 NADH e-: CoQ 10acts after complex I FADH e2: CoQ 10acts after complex II Small protein Cyt c NADH and FADH e-: 2yt c acts after complex III
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