BIO 118 1st Edition Lecture 7 Outline of Last Lecture I Tour of the Cell a All Cells Have b Grouping Cells c Prokaryotic Cells Structural Overview d Prokaryotic Cells Genetic Information e Prokaryotic Cells Internal Structure f Prokaryotic Cells External Structure g An Introduction to Eukaryotes h Eukaryotic Cells i Eukaryotes and Prokaryotes Compared j The Nucleus k Rough Endoplasmic Reticulum l Smooth Endoplasmic Reticulum m Golgi Apparatus n Ribosomes o Peroxisomes p Lysosomes q How are materials delivered to lysosomes r Vacuoles s Mitochondria t Chloroplasts u The Cell Wall v Cytoskeleton w Cell Systems 1 Nuclear Transport x Cell Systems 2 The Endomembrane System y The Signal Hypothesis z How are products shipped from the Golgi aa Cell Systems 3 The Dynamic Cytoskeleton bb Three Types of Cytoskeletal Elements Outline of Current Lecture I Introduction to Metabolism a Two types of energy b First Law of Thermodynamics c Seconds Law of Thermodynamics d What is Free Energy 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 e f g h i j k l m n Some Important Energy Changes in Chem Reactions Gibbs Free Energy Change What Drives Nonspontaneous Endergonic Reactions Energetic Coupling Role of Redox Reactions in Metabolism What is a Redox Reaction Electrons Are Usually Accompanied by Protons Role of ATP in Metabolism ATP Hydrolysis Protein Phosphorylation How Does ATP Drive Endergonic Reactions Current Lecture Two Types of Energy Kinetic Energy o Energy of motion o Molecular level thermal energy i e heat or light Ex Electrons falling to lower energy shell Potential Energy o Energy of position or configuration o Molecular level chemical energy Stored in the position of the electron If close to negative charges of other electrons and far from positive charges of nuclei potential energy is HIGH First Law of Thermodynamics Energy is conserved o Energy cannot be created or destroyed o Energy can only be transferred transformed Chemical reactions involve such energy transformations Second Law of Thermodynamics States that entropy always increases o Chemical reactions result in products with less usable energy Physical and chemical processes proceed in the direction that results in lower potential energy enthalpy increased disorder entropy which together are measured by free energy What is Free Energy Free Energy G of a reaction is the amount of energy available to do work G is the CHANGE in free energy and it determines whether a reaction si spontaneous or requires added energy to proceed o Combined contribution of change in heat content H i e chemical potential energy disorder of the system S i e entropy as well as the overall temperature where temp is measured in Kelvin o Formula G H T S Some Important Energy Changes in Chem Rx s Enthalpy A measure of the total energy of a molecule o Includes the potential energy of the molecule heat content o Plus pressure and volume effects of the molecule H is the CHANGE in enthalpy in chemical reactions o H H products H reactants H is negative when a reaction releases heat energy H products is smaller than H reactants In this case we say the reaction is exothermic Entropy Measure of the amount of disorder of a system S is the change in entropy in chemical reactions o S S products S reactants When products are less ordered than reactants entropy of the products is higher than that of reactants Entropy increases if S is positive Gibbs Free Energy Change G o G H T S o H change in enthalpy A measure of chemical potential energy o S change in entropy A measure of disorder o T Temperature of Molecules o Note from formula that at higher temps the change in entropy exerts greater effect on G G as a determinant of whether Rx is spontaneous Spontaneous chemical reactions run in the direction that lowers the free energy of the system G 0 Exergonic reaction spontaneous energy released G 0 Endergonic reaction non spontaneous require energy input G 0 Reactions at equilibrium What Drives Nonspontaneous Endergonic Rx s An input of chemical energy o Recall how exergonic rx s release free energy Energetic coupling o Between exergonic and endergonic reactions o Allows chemical energy to be released from one reaction to drive another reaction Energetic Coupling In cells it occurs on one of two ways o Transfer of high energy electrons Redox reactions o Transfer of phosphate group ATP hydrolysis Role of Redox Reactions in Metabolism Reduction oxidation reactions redox reactions o Chemical reactions that involve electron transfer o When an atom molecule gains an electron reduced o Reduction gain one or more electron and a hydrogen ion H What is a Redox Reaction o When an atom or molecule loses an electron oxidized o Oxidation loss of one or more electrons o Oxidation and reduction events are always coupled If an atom loses an electron another has to gain it Electron donors are always paired with electron acceptors OIL RIG o Oxidation is Loss Reduction is Gain Electrons Are Usually Accompanied by Protons Each electron transferred from one molecule to another during a redox reaction is usually accompanied by a proton hydrogen ion H A reduced molecule o Gains a proton and has higher potential energy An oxidized molecule o Loses a proton and has lower potential energy Understanding where oxidation and reduction occur is often not always a matter of following hydrogen atoms o Reduction often adds H s o Oxidation often removes H s Role of ATP in Metabolism ATP adenosine triphosphate o o o o o ATP is the cellular currency for energy Provides the fuel for most cellular activities Has high potential energy Allows cells to do work Works by Phosphorylating target molecules transferring a phosphate group ATP Hydrolysis Protein Phosphorylation Hydrolysis of ATP is exergonic because o The entropy of the product molecules is much higher than that of the reactants Energy released during ATP hydrolysis o Is transferred to a protein during phosphorylation o Usually causes a change in the protein s shape How Does ATP Drive Endergonic Reactions Energetic Coupling o When a protein is phosphorylated the exergonic phosphorylation reaction is with an endergonic reaction Reactant molecules in an endergonic reaction are phosphorylated The free energy released during phosphorylation is coupled to the endergonic reaction to make the combined overall reaction exergonic o Energetic Coupling through
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