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INTRODUCTION TO METABOLISM.

INTRODUCTION TO METABOLISM. Chapter 6 Metabolism, Energy, and Life. Objectives. Explain the role of catabolic and anabolic pathways in cell metabolism Distinguish between kinetic and potential energy Distinguish between open and closed systems

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INTRODUCTION TO METABOLISM.

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  1. INTRODUCTION TO METABOLISM. Chapter 6 Metabolism, Energy, and Life

  2. Objectives • Explain the role of catabolic and anabolic pathways in cell metabolism • Distinguish between kinetic and potential energy • Distinguish between open and closed systems • Explain the first and second Laws of Thermodynamics • Distinguish between entropy and enthalpy • Understand the Gibbs equation for free energy change • Understand how “usable” energy changes with changes in enthalpy, entropy, and temperature • Understand the usefulness of free energy

  3. Metabolism • The sum of all the chemical processes occurring in an organism at one time • Concerned with the management of material and energy resources within the cell • Catabolic pathways • Anabolic pathways

  4. Catabolic Pathways • Pathways that release energy by breaking down complex molecules into simpler compounds • Cellular respiration • C6H1206 + 6O26CO2 +6H20 + ENERGY

  5. Anabolic Pathways • Pathways that consume energy to build larger, complicated molecules from simpler ones • Polymerization • Photosynthesis6CO2 +6H20 + light  C6H1206 + 6O2

  6. Bioenergetics • Study of how organisms manage their energy resources • Energy is the capacity to do work, to move matter • Kinetic energy: energy that is in motion • Potential energy: stored energy based on location or structure • The rearrangement of atoms in molecules may result in the potential energy of the molecule being converted into kinetic energy

  7. Energy LawsLaws of Thermodynamics • The terms open or closed systems refer to whether or not energy can be transferred between the system and its surroundings (can energy be imported or exported) • First Law of Thermodynamics: Energy can neither be created nor destroyed, only transformed from one type to another • Second Law of Thermodynamics: Each energy transformation results in less usable (ordered) energy

  8. Enthalpy or work total energy is a measure of all the energy in a system Symbolically represented as “H” Entropy is a measure of randomness (disorder) Symbolically represented as “S” Free EnergyG=H-TS Free energy (G) is the portion of system energy that can do work under uniform temperature Temperature (T) is measured in 0K

  9. G • The higher the G the more unstable the system • A change in free energy can occur with metabolism • Exergonic: reactions that lose energy; -G • Endergonic: reactions that gain energy; + G • Metabolic reactions are often coupled where an exergonic reaction might fuel an endergonic reaction • When G = 0 no work can be done • When reactions go to equilibrium, G = 0(therefor metabolic reactions do not usually reach an equilibrium) • Energy needed for Mechanical, Chemical, and Transport workings of the cell

  10. Objectives • Explain the role of ATP in the cell • Describe ATP’s composition and how it performs cellular work • Explain the importance of chemical disequilibrium • Understand the energy profile of a reaction including: activation energy, free energy change, & transition state • Describe the role and mechanisms of enzymes • Explain how enzyme activity can be controlled by environmental factors, cofactors, enzyme inhibitors, and allosteric regulators • Distinguish between allosteric activation and cooperativity • Explain how metabolic pathways are regulated

  11. ATP • Energy molecule used to couple exergonic reactions to endergonic • Nucleotide with three phosphate groups attached to the ribose sugar • ATP has a high G

  12. ATP • Energy is released from ATP through the loss of phosphate groups • Catabolic reaction resulting from hydrolysis producing ADP + Pi (inorganic Phosphate) + energy (G = -7.3Kcal/mol in the lab, -13Kcal/mol in the cell)

  13. How ATP works • Hydrolysis of ATP produces inorganic phosphate that is attached to a molecule involved in an endergonic process • Phosphorylation is the process of ATP transferring phosphate to a molecule • Results in a phosphorylated intermediate

  14. Regeneration of ATP • ATP loses energy when it phosphorylates an intermediate molecule of an endergonic reaction. ATP becomes ADP • Regeneration of ATP occurs when inorganic phosphate (Pi) is bound to ADP utilizing energy supplied by a catabolic reaction

  15. Cell Efficiency • ATP is a good energy source because: • It can participate in a many different kinds of reactions within the cell • Usually is directly involved in reactions • Little wasted energy during phosphorylation of an intermediate • Enzymes • Regulation of reactions

  16. Enzymes • Enzymes are proteins • Specific because of conformational shape • Enzymes are catalysts • Catalyst: chemical that changes the rate of a reaction without being consumed • Recycled • Enzymes reduce the activation energy of a reaction • Amount of energy that must be added to get a reaction to proceed

  17. Activation Energy • EA= Activation energy • EA is usually supplied by heat • Reactants absorb heat increasing G making the reactants unstable so they react

  18. How Enzymes Function • Enzymes are substrate specific • Substrate: any molecule to which an enzyme will bind • Although an enzyme can be a large protein, only a specific region of the enzyme interacts with the substrate • Active Site: region of enzyme that “reacts” to substrate • As enzyme and substrate bind, the enzyme shape is modified to better fit the substrate • Induced fit occurs as a result of the enzyme substrate complex

  19. Enzyme activity • The rate at which an enzyme can function is dependant on several factors including: • Temperature • pH • The rate of reaction is also influenced by the concentration of the substrate or enzyme • Some enzymes utilize inorganic or organic molecules as helpers • Cofactor: inorganic molecule (mineral) • Coenzyme: organic non-protein molecule (vitamin)

  20. Enzyme Inhibitors • Enzyme activity may be reduced by molecules attaching to the enzyme. • Inhibition may occur at two different locations • competitive inhibition: inhibitor mimics molecule that attaches to active site • noncompetitive inhibition: inhibitor binds to enzyme away from the active site resulting in modification of active site

  21. Control of Metabolism • Allosteric Regulation: enzyme function may be stimulated or inhibited by attachment of molecules to an allosteric site • Feedback Inhibition: end product of metabolic pathway may serve as allosteric inhibitor • Cooperativity: single substrate molecule primes multiple active sites increasing activity

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