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BU BIOL 118 - An Introduction to the Metabolism
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BIO 118 1st Edition Lecture 7 Outline of Last Lecture I. Tour of the Cella. All Cells Haveb. Grouping Cellsc. Prokaryotic Cells- Structural Overviewd. Prokaryotic Cells- Genetic Informatione. Prokaryotic Cells- Internal Structuref. Prokaryotic Cells- External Structureg. An Introduction to Eukaryotesh. Eukaryotic Cellsi. Eukaryotes and Prokaryotes Comparedj. The Nucleusk. Rough Endoplasmic Reticuluml. Smooth Endoplasmic Reticulumm. Golgi Apparatusn. Ribosomeso. Peroxisomesp. Lysosomesq. How are materials delivered to lysosomesr. Vacuoless. Mitochondriat. Chloroplastsu. The Cell Wallv. Cytoskeletonw. Cell Systems 1: Nuclear Transportx. Cell Systems 2: The Endomembrane Systemy. The Signal Hypothesisz. How are products shipped from the Golgi?aa. Cell Systems 3: The Dynamic Cytoskeletonbb. Three Types of Cytoskeletal ElementsOutline of Current Lecture I. Introduction to Metabolisma. Two types of energyb. First Law of Thermodynamicsc. Seconds Law of Thermodynamicsd. 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. Some Important Energy Changes in Chem Reactionsf. Gibbs Free Energy Changeg. What Drives Nonspontaneous, Endergonic Reactionsh. Energetic Couplingi. Role of Redox Reactions in Metabolismj. What is a Redox Reaction?k. Electrons Are Usually Accompanied by Protonsl. Role of ATP in Metabolismm. ATP Hydrolysis & Protein Phosphorylationn. How Does ATP Drive Endergonic Reactions?Current LectureTwo Types of Energy- Kinetic Energyo Energy of motiono @ Molecular level= thermal energy (i.e. heat or light) Ex. Electrons falling to lower energy shell- Potential Energyo Energy of position or configurationo @ 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 HIGHFirst Law of Thermodynamics- Energy is conservedo Energy cannot be created or destroyedo Energy can only be transferred & transformed- Chemical reactions involve such energy transformationsSecond Law of Thermodynamics- States that entropy always increaseso 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 energyWhat is Free Energy?- Free Energy (G) of a reaction is the amount of energy available to do work- ΔG is the CHANGE in free energy and it determines whether a reaction si spontaneous or requires added energy to proceedo 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 Kelvino Formula: ΔG = ΔH-TΔSSome Important Energy Changes in Chem Rx’s- Enthalpy: A measure of the total energy of a moleculeo Includes the potential energy of the molecule (‘heat content)o Plus pressure and volume effects of the molecule- ΔH is the CHANGE in enthalpy in chemical reactions o ΔH= H(products)-H(reactants) ΔH 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- ΔS is the change in entropy in chemical reactionso ΔS= S(products)-S(reactants) When products are less ordered than reactants, entropy of the products is higher than that of reactants- Entropy increases if ΔS is positive- Gibbs Free Energy Change= ΔGo ΔG= ΔH-TΔSo ΔH= change in enthalpy A measure of chemical potential energyo ΔS= change in entropy A measure of disordero T= Temperature of Moleculeso Note from formula that at higher temps, the change in entropy exerts greater effect on ΔGΔG as a determinant of whether Rx is spontaneous- Spontaneous chemical reactions run in the direction that lowers the free energy of the system- ΔG < 0: Exergonic reaction: spontaneous, energy released- ΔG > 0: Endergonic reaction: non-spontaneous, require energy input- ΔG = 0: Reactions at equilibriumWhat Drives Nonspontaneous, Endergonic Rx’s?- An input of chemical energyo Recall how exergonic rx’s release free energy- Energetic couplingo Between exergonic and endergonic reactionso Allows chemical energy to be released from one reaction to drive another reactionEnergetic 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 transfero When an atom/molecule gains an electron= reducedo 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= oxidizedo Oxidation= loss of one or more electronso 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 RIGo Oxidation is Loss; Reduction is GainElectrons 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” moleculeo Gains a proton and has higher potential energy- An “oxidized” moleculeo Loses a proton and has lower potential energy- Understanding where oxidation and reduction occur is often (not always) a matter of following hydrogen atomso Reduction often adds H’so Oxidation often removes H’sRole of ATP in Metabolism- ATP= adenosine triphosphateo ATP is the cellular currency for energyo Provides the fuel for most cellular activitieso Has high potential energyo Allows cells to do worko Works by: Phosphorylating target molecules transferring a phosphate groupATP 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 hydrolysiso Is transferred to a protein during phosphorylationo Usually causes a change in the protein’s shapeHow Does ATP Drive Endergonic Reactions- Energetic Coupling o When a protein is phosphorylated, the exergonic phosphorylation reaction is with an endergonic reaction Reactant molecules


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BU BIOL 118 - An Introduction to the Metabolism

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