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An Introduction to Metabolism

An Introduction to Metabolism. Metabolism, energy and life Enzymes The control of metabolism. Metabolism. Metabolism- totality of an organism’s chemical reactions. Metabolism. Catabolic pathways - release energy by breaking down complex molecules to simpler compounds. Metabolism.

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An Introduction to Metabolism

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  1. An Introduction to Metabolism Metabolism, energy and life Enzymes The control of metabolism

  2. Metabolism • Metabolism- totality of an organism’s chemical reactions

  3. Metabolism • Catabolic pathways- release energy by breaking down complex molecules to simpler compounds

  4. Metabolism • Anabolic pathways- consume energy to build complex molecules from simpler compounds

  5. Energy • Energy- capacity to do work • Kinetic energy- the energy of motion • Potential energy- the capacity to do work, energy stored as a result of its location or structure • Chemical energy- form of potential energy- stored in molecules as a result of the arrangement of the atoms

  6. Metabolism, energy, and life • Metabolism = anabolism + catabolism • Metabolic reactions are organized into pathways • Energy: kinetic and potential

  7. Thermodynamics • Thermodynamics- study of energy transformations • The First Law- the energy of the universe is constant • Energy can be transferred and transformed but it cannot be created or destroyed • “principle of conservation of energy”

  8. Thermodynamics • The Second Law- Every energy transfer or transformation increases the entropy of the universe • Entropy- the measure of disorder

  9. Free Energy- the portion of a system that can perform work • It is available for work • Symbol is G

  10. Exergonic reaction- “energy outward” Proceeds with a net release of free energy Occurs spontaneously Endergonic reaction- “energy inward” absorbs free energy from its surroundings nonspontaneous Energy Coupling- the use of an exergonic process to drive an endergonic one

  11. Cells are kept alive with a flow of energy The products of a reaction become the reactants of the next reaction.

  12. Rube Goldberg Machine

  13. Cellular Work • 1. Mechanical work • 2. Transport work • 3. Chemical work

  14. ATP • Adenosine Triphosphate • Adenine bonded to ribose RNA has one phosphate group attached to ribose ATP has three phosphate groups attached to ribose

  15. ATP to ADP • Phosphate bonds- broken by hydrolysis • Without 3rd Phosphate Group= Adenosine Diphosphate (ADP) and inorganic phosphate

  16. ATP + H2O → ADP + Pi Test tube: Change in G = -7.3 kcal/mol Cell: Change in G= -13 kcal/mol

  17. ATP to ADP Is this reaction Exergonic or Endergonic? • Exergonic- ADP is more stable than ATP, energy is released with the loss of Pi • Negative G value

  18. Phosphorylation • Pi is not transferred into solution, given to another compound • Compound receiving the Pi is phosphorylated.

  19. ATP cycle ATP + H2O → ADP + Pi Change in G =-7.3 kcal/mol ADP + Pi → ATP + H2O Change is G = 7.3 kcal/mol

  20. Enzymes Catalyst- chemical agent that changes the rate of a reaction without being consumed by the reaction Enzyme- catalytic protein

  21. Activation Energy or “free energy of activation” – the energy required to break the bonds in the reactants • Symbol- EA

  22. Cellular issue with heat

  23. Induced fit hypothesis • Change in the shape of an enzyme’s active site, which is induced by the substrate.

  24. Enzyme-substrate complex • Substrate held by weak interactions- hydrogen and ionic bonds • R-groups of amino acid chain of the protein catalyze the substrate

  25. Lowering the EA Active site • Stresses critical bonds that must be broken • Can provide a microenvironment Ex: Acidic R groups form a pocket of low pH • Brief bonding- covalent bonding between substrate and R groups

  26. Rate of reaction • Determined by the concentration of substrate and enzyme • Saturation point

  27. Temperature and pH Optimal Temperature Optimal pH

  28. Cofactors • Bind to active site permanently or loosely • Inorganic • Organic- coenzyme

  29. Inhibitors • Competitive inhibitors- block active site • Noncompetitive inhibitors- bind to another part of enzyme • Types: poison, antibiotics

  30. When is it useful to inhibit enzymes?

  31. Allosteric regulation • Allosteric site- specific receptor site on enzyme away from active site • Can activate or inhibit

  32. Feedback inhibition Most common Pathway switch off by its end product

  33. Cooperativity • Substrate induces enzyme to accept more substrates

  34. Multienzyme complex Team of enzymes assembled together Ex: Mitochondria in eukaryotic cells- enzymes for respiration are clustered together

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