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ENERGY

ENERGY. Intro to Cellular Metabolism. Metabolism:. Metabolism – totality of an organism’s chemical reactions Catabolic pathways – metabolic path that releases energy by breaking down complex molecules into simpler molecules

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ENERGY

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  1. ENERGY Intro to Cellular Metabolism

  2. Metabolism: • Metabolism – totality of an organism’s chemical reactions • Catabolic pathways – metabolic path that releases energy by breaking down complex molecules into simpler molecules • Anabolic pathways – metabolic path that consumes energy to build complex molecules from simpler molecules

  3. Forms of Energy (capacity to cause change) • Radiant: sunlight, EM waves • Chemical: Glucose, ATP, Starch • Kinetic: Molecular movement (diffusion, osmosis) • Heat • Mechanical: Muscle contraction

  4. 1st Law of Thermodynamics • Energy may neither be created nor destroyed; it may only be transferred or transformed. • Thus in a closed system the total energy remains constant.

  5. Closed vs. Open Systems • Organisms are open systems that exchange materials with their environments

  6. 2nd Law of Thermodynamics • At every energy transfer, some energy is lost to the system (usually in form of heat) • This loss increases entropy (disorder)

  7. Large Scale • Energy flows into ecosystems as heat and exits as heat radiated into space

  8. Small Scale • Animals take in organized forms of matter and energy & replace them with less ordered forms. OrderedLess ordered • Starch • Proteins catabolized CO2, H2O • Lipids

  9. A word about “order” • Systems rich in energy are highly ordered • Examples: • Complex molecules • Human beings • Smaller parts (e.g. monomers of macromolecules) have less energy and are less ordered

  10. Spontaneous processes • Reactions that occur without outside help. Ex: water flowing downhill • Release energy • For a rxn to be spontaneous, it must increase entropy of universe

  11. Spontaneous reactions

  12. Non-spontaneous processes • Require an input of energy • Ex: Synthesize a protein • Decrease entropy in a system • (a protein is more ordered than it’s amino acid monomers)

  13. Non-spontaneous reactions

  14. Gibb’s Free Energy • Free energy (G) is the portion of a system’s energy that can perform work. • Free Energy Change: ΔG = ΔH – TΔS • H = total energy (enthalpy) • T = degrees in K • S = entropy • OR: ΔG = G(final state) – G(initial state)

  15. Spontaneous Rxn: ΔG = ΔH – TΔS • For a rxn to be spontaneous, ΔG must be negative • Either decrease enthalpy (total energy) • Or increase entropy (give up order)

  16. Endergonic vs. Exergonic • Endergonic rxn – absorbs free energy from surroundings (ΔG is positive) • Creates more order (anabolic) • Exergonic rxn – releases free energy into surroundings (ΔG is negative) • Creates more disorder (catabolic)

  17. Metabolic Equilibrium( a very, very bad thing) • Reactions in a closed system reach equilibrium • ΔG will be 0; no work can be done. • A cell that reaches metabolic equilibrium is dead!

  18. Key to preventing equilibrium = • The product of one reaction becomes the reactant in the next. • i.e. Products do not accumulate • Energy coupling: the use of an exergonic reaction (release energy) to power an endergonic (requires energy) reaction.

  19. Example:

  20. ATP! (adenosine triphosphate) • Energy source that powers cell’s activities

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