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Understanding Metabolism, Energy Transformations, and Enzymatic Reactions

This lecture explores the fundamentals of metabolism and the role of enzymes in energy transformations. We delve into kinetic, thermal, and potential energy, highlighting the principles of thermodynamics. Key concepts include Gibbs free energy (ΔG) and the distinctions between spontaneous and non-spontaneous reactions, along with exergonic and endergonic processes. We also examine the significance of equilibrium in metabolic reactions and provide illustrative examples such as respiration and photosynthesis, emphasizing how energy is transferred within biological systems.

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Understanding Metabolism, Energy Transformations, and Enzymatic Reactions

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  1. Lecture #7 Introduction to Metabolism & Enzymes

  2. Energy • the capacity to cause change • the ability to do work • Kinetic Energy • Thermal energy • Potential Energy

  3. Thermodynamics • The study of energy transformations that occur • Law #1 – Energy can neither be created nor destroyed; it can only be transferred and transformed

  4. Chemical Potential Energy A + B ↔ C + D The potential energy available for release in a chemical reaction Potential energy - stored energy that can be used to transfer energy from one system to another

  5. G and DG • Gibbs free energy - the energy portion of a system available to do work – when temperature and pressure are constant • DG – the change in free energy that happens when a system changes DG = Gend – Gstart

  6. What DG means…. A + B ↔ C + D • if DG is negative – the ending free energy is lower than the starting free energy • therefore, there has been a release of energy – energy must have been transferred or transformed – spontaneous reaction • If DG is positive – the ending free energy is higher than the starting free energy • Energy is absorbed by the system - non-spontaneous reaction

  7. Exergonic reaction • energy is released • the DG value is less than 0 (negative) • spontaneous • the DG value represents the theoretical maximum amount of work (quantity of energy that can be transferred to another system) • Endergonic reaction • energy is absorbed and stored • the DG value is grater than 0 (positive) • non-spontaneous • the DG value represents the amount of energy required to drive the reaction

  8. Respiration/Photosynthesis C6H12O6 + O2↔ 6CO2 + 6H2O forward reaction: DG = -686 kcal/mol reverse reaction: DG = 686 kcal/mol

  9. Equilibrium • balance • when a chemical reaction proceeds at the same rate as its reverse reaction, with no change in the amount of each compound • lowest possible free energy (G) value • a system in balance cannot spontaneously change • Must push the system away from the balance

  10. Equilibrium in Metabolism? C6H12O6 + O2→ 6CO2 + 6H2O O2 O2 C6H12O6 + O2→ 6CO2 + 6H2O C6H12O6 CO2 C6H12O6 CO2

  11. ATP Pi ATP ADP DG=-7.3 kcal/mol P

  12. Ca2+-ATPase – skeletal muscle Ca2+ Ca2+ Ca2+ CYTOPLASM ATP P Ca2+ Ca2+ Ca2+ ER LUMEN Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+

  13. Enzymes • a protein catalyst • catalyst – speeds up a chemical reaction

  14. E + S ↔ ES ↔ E + P

  15. E + S ↔ ES ↔ E + P

  16. E + S ↔ ES ↔ E + P

  17. Continued tomorrow and in today’s lab session……..

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