LS2 Lec 4 Enzymes (4 Slides)

LS2 Lec 4 Enzymes (4 Slides) - Proteins • Proteins made...

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Unformatted text preview: Proteins • Proteins made inside the cell are found Life Sciences 2 Energy, Enzymes, & Metabolism Chapter 8 Dr. Joseph Esdin Energy, Enzymes, and Metabolism – Embedded or attached to the plasma membrane – In the cell cytosol Chemical Reaction Anabolic Reaction Catabolic Reaction • In living organisms, thousands of enzyme catalyzed reactions occur • Catalysis occur due to the 3-D shape of the proteins involved • Metabolism is the combination of all of these reactions Reactions build macromolecules Reactions breakdown macromolecules 1 Energy and the Laws of Thermodynamics • Bioenergetics is the flow of energy in biochemical systems • Energy is defined as the capacity to do work • Forms of Energy: Heat, light, electrical, and chemical Energy and the Laws of Thermodynamics • Kinetic energy is the energy associated with motion focus on in chemical bonds Energy and the Laws of Thermodynamics • Potential energy is the energy of state or position Energy and the Laws of Thermodynamics energy is never created nor Energy before and after transformation is equal (no energy is created or lost) After energy transformation The amount of energy available to do work is less energy is still therebut becomes unusable 2 Energy and the Laws of Thermodynamics Energy and the Laws of Thermodynamics • With repeated energy transformations usable energy decreases and unusable energy increases entropy • With repeated energy transformations usable energy decreases and unusable energy increases occurs in a closed system Energy and the Laws of Thermodynamics Energy and the Laws of Thermodynamics 1st law 2nd law • Quantity Vs. Quality always same usable vs. unusable In a closed system, no energy or matters enters or leave ex: universe or container no exchange w/ environment 3 Where Does Living Matter Get Its Energy From? Waste materials leave Why Do Cells Need Energy? • Exergonic reaction – Energy is released as the reaction proceeds to form products • Endergonic reaction exchange of energy/ – Energy is needed to start the reaction Raw chemicals materials enter ATP: energy usage open system nutrients: Energy production Chemical Reactions Release or Take Up Energy starch--> ex: breaking down into monomers, Exergonic Reaction releasing energy – Non-spontaneous reaction glucose Exergonic Reaction • Energy is released as the reaction proceeds to form products. !G is negative free energy Endergonic Reaction glucose-->starch because product has less energy 4 Exergonic Reaction • Spontaneous reaction, that goes to completion over time without any energy input. It releases energy by breaking bonds • G product < G reactant ==> !G is negative • Glucose +O2 -> 6 CO2 + H2O + energy in the cell, both reactions happen Biochemical at the same time Reactions Exergonic reaction !G= -7.3 kcal/mol Endergonic reaction !G= +3.4 kcal/mol starting, reactant Glutamate Glutamine Substrate Product !G= -3.9 kcal/mol exergonic reactions are needed in the cell to power endergonic reaction Endergonic Reaction • Non-spontaneous reaction • Needs energy • G reactant < G product ==> ! G is positive Biochemical Reaction yield of chemical reaction • Thermodynamics: relates to !G. This determines the direction but not the speed of the reaction • Kinetics: describes the rate of the reaction • Glucose +O2 -> 6 CO2 + H2O + energy • !G = -686 kcal/mole proteins only change the k inetics not actual reaction 5 Biochemical Reaction • Sugar + Oxygen = Sugar + Oxygen – No reaction will happen • Sugar + Oxygen = Heat + CO2 + Spark enzymes act as a push for the reaction to occur • (Activation Energy Ea) Activation Energy • Even though some chemical reactions have a negative !G, they can not proceed without an aid • !G determines the direction of a reaction but not its rate • To initiate a reaction, Ea is needed enzymes lower this but don't effect G Activation Energy exergonic reaction Activation Energy • The rate of the reaction depends on the activation energy. How can we increase the reaction rate? 6 How to Increase the Rate of Reaction? • Add heat Enzymes • Cells can control the speed of reactions by using protein catalysts called enzymes • Reactant • Activation energy Enzymes • Enzymes enhance the speed of biochemical reactions Enzyme Properties Substrate fits precisely into the active site • The enzymes are not changed • They alter the rate of the reaction – They lower the activation energy of the reaction • They do not change !G Nonsubstrate does not do not change outcome Enzymes is a protein with a binding site capable of binding one or more substrate molecules enzymes are s pecifi c to the s ubstrate 7 Enzymes Enzymatic Interaction The fit of a substrate to the enzyme is highly specific based on shape, H-bonds, hydrophobic interactions binds via chemical bonds beta cells release insulin (hormone) to adverseley lower glucose level G does not change w/ or w/o enzyme alpha cells have glucagon, which has a role to raise blood sugar ( ex. during sleep when your body is low on glucose Specific Enzymatic Action acts as glucostat Optimal Conditions may denature • pH • Temperature • Substrate concentration found in pancreas, liver, small intestine enzyme hexokinase --> An enzyme binds to a substrate at the active site to form enzyme-substrate complex glucose to glucose 6phosphate universal enzyme, found in many species iso forms I, II, III & IV important in humans Hexokinase modulates amount of sugar in blood excess sugar = glycogen synthesis in the liver 8 mouth Optimal Conditions Optimal Conditions stomac h diff enzymes require diff pH concentration of substrate Optimal Conditions 98.6 in humans Can Enzymes be Regulated? • Cofactors: positively charged metals, ions, that bind to protein to make it more functional (not organic) • Coenzymes: organic w/ carbon interact w/ enzymes backbone • Prosthetic groups: permanently bound to protein (ex. hemoglobin to Fe permanently) can aslo be changed during reaction point of saturation= all enzymes are being active 9 makes muscles not rest, makes them more active than normal causing fatigue inhibits acetyl cholinesterase Nerve gas: DIPF competing w/ substrate or not Can Enzymes Be Inactivated? Irreversible Inhibition in muscles acetylcholine • Inhibitors (competitive or non competitive) turning on/off – Natural – artificial enzyme ex: toxicity • Feedback loops • Allosteric regulation always rest period for cell to replensih as acetylcholine rests, acetylcholinesterase holds down acetyl choline to allow it to rest temporary blockade Reversible Inhibition inhibitor F substrate compete for active site Reversible Inhibition inhibitor acts at a diff site & makes the active site unavailable the one that wins is the one w/ the higher concentration in the solution 10 Feedback Loop Inhibition and Feedback Loop • The production of the final product stops the reaction from recurring final product inhibits first reaction reaction maintains homeostastis sickle cell anemia: caus is mutaiton in hemoglobin Proteins & Medicine Regulation of Proteins • This regulation does not apply to enzymes only • It applies to any type of protein located in the cytosol or embedded within the membrane crescent shape Sickle-cell phenotype unable to bind oxygen and travel to every part of body Normal phenotype main function to transport oxygen in a body diseases: protein that is not functioning because inhibited or over-functioning & is overactive 11 normally we have LDL receptors low-density lipo-proteins meant to collect c holesterol in the liver cells Proteins & Medicine Proteins & in disease, there are dysfunctional Medicine LDL receptors buildup of cholesterol in blood lipids in water build up too much cholesterol in the blood in blood vsesels & can block Mutation: wrong sequence of A.A. FH: familial hyper cholesterolemia glutamic acid (neg charge) is substituted w/ valine (0 charge) Demonstration of change of shape genetic disease Enzymes & Medicine • Phenylketonuria (PKU): Disease caused by mutation in the enzyme phenylalanine hydroxylase in the liver • Very rare 1/12000 • 451 amino acid enzyme function is to • Arginine 408 tryptophan buildup of impede other functions hydrolyze phenylaline Enzymes & Medicine • Prozac: Serotonin uptake inhibitor • Cocaine: Prevents Dopamine uptake • Caffeine: Competes with adenosine • Curare: Death from muscle paralysis • Cyanide: Lethal (Cytochrome C) those w/ PKU have mutated phenylaline hydroxylase to manage disease: prevent ingestion of phenylaline ex: equal has phenylaline sugar 12 Synapse Synapse pre-synaptic zoom!!! Neurotransmitter release of c hemicals released to activate c ell on other end post s ynaptic Synapse Synapse • Presynaptic neuron neuro transmitters dont' stay – Axon terminals – Vesicles filled with neurotransmitters • Postsynaptic neuron – Dendrites constantly being used and broken down 13 depression=chemical imbalance: lack serotonin (neurotransmitter) suffi cient amount released from pre-->post syn. cell normally is broken down drugs to treat keep serotonin available for a longer amt of time Prozac, an Inhibitor interfere w/ • Fluoxetine recycling Hydrochloride of it • (Selective serotonin Reuptake Inhibitor)SSRI inhibits breakdown of serotonin keep it for longer therefore alleviates symptoms of depression Cocaine, an Inhibitor • Stimulant and appetite suppressant • Dopamine Transporter protein (DAT) blocker – Dopamine reuptake inhibitor keeps dopamine available for longer by blocking DAT to stop transport of Dopamine sigmund Freud tried to cure morphine addition by giving them cocaine Caffeine, an Inhibitor Caffeine in plants CNS stimulant, cardiac stimulant 200 mg Increase alertness, wakefulness Restlessness, loss of motor control Does not eliminate the need for sleep, it minimizes sensation of being tired • Adenosine receptor antagonist • Increase dopamine activity makes dopamine available for longer by inhibiting adenosine receptor • • • • • • normal process is to break down dopamine caffeine makes a nerve transmitter available for a longer amount of time ACH Curare, an Inhibitor causes muscle activity to occur • Blocks ACh receptors • Used as poison • Used as a relaxant with anesthetic agents curare is used as poison • Anesthesia awareness making muscles temporarily paralyzed given enough muscle relaxant but not enough pain suppresant 14 ...
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This note was uploaded on 10/26/2011 for the course LS 2 taught by Professor Pires during the Spring '08 term at UCLA.

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