Metabolism

1. Metabolism Enzymes Metabolism and Metabolic Pathways

2. Enzymes • Proteins which function as biological catalysts • Each biochemical transformation in a cell has a specific enzyme associated with it

3. Enzymes and Activation Energy

4. Lock and Key Model • Interaction between enzyme and substrate analogous to a lock and key • Active site • Allosteric sites

6. Kinetics of an Enzymatically Catalyzed Reaction • Conversion of substrate to product • Concentration of substrate and enzyme constant • All experimental conditions (pH, temp) constant

7. Effect of [S] on V0 • Initial linear relationship between increasing [S] and initial reaction velocity • Saturation kinetics • Overall a hyperbolic curve

8. Michaelis-Menton Kinetics • Vmax • Maximum reaction rater • KM • Affinity constant • [S] when V0 = 1/2 Vmax • Values can be estimated from hyperbolic graph

9. Lineweaver - Burke Plots • Linearizes Michaelis-Menton plot • Plot 1/V0 vs 1/[S]

10. Monod Equation

11. Metabolism

12. Definitions • Metabolism: The sum of the biochemical reactions which occur in a cell • Pathway: • A series of connected reactions • A --> B--> C-->D-->E • Catabolism: • Breakdown complex substrates • Generally oxidations

13. Energy yielding • Generate reduced electron carriers • Anabolism • Build up complex molecules from precursors • Generally reductions • Energy requiring • Oxidize electron carriers

14. ATP and Energy Transfer • ATP <---> ADP <---> AMP • High energy (squiggle) phosphate bonds • 7.3 kcal to make or break these bonds • Transfer energy from energy yielding reactions to energy requiring reactions

16. Mechanisms of Energy Generation • Substrate level phosphorylation • Oxidative phosphorylation • Photophosphorylation

17. Electron Carriers • Coenzymes • NAD/NADH + H+ • FAD/FADH2 • Transfer electrons from oxidation to reduction reactions • Need for initial electron donor and terminal electron acceptor

18. NAD/NADH + H+

19. Understanding Metabolic Pathways • Keep track of: • Elements • Energy (ATP/ADP) • Electrons • Why are there so many steps in the pathways • Energetic constraints • Generation of intermediates

20. Central Metabolic Pathways • Essential pathways • Found in all organisms • Include: • Glycolysis (EMP) • TCA (Kreb’s) cycle • ETS

21. Other Pathways • Specific catabolic pathways not found in all organisms • If an organism can convert a compound into an intermediate in Central metabolism, complete mineralization (catabolism to carbon dioxide and water) is possible.

22. Overview of Pathways

23. Conversion of glucose to 2 pyruvate Most common pathway for initial metabolism of glucose Anaerobic pathway Substrate level phosphorylation Low energy yield/incomplete oxidation Production of NADH + H+ Glycolysis

25. Fermentation • Reoxidation of NADH + H+ to NAD • Organic compound functions as a terminal electron acceptor • Important in • Industrial production of chemicals • Food production: bread, wine, etc.

26. TCA Cycle • Oxidation of pyruvate to carbon dioxide • Low direct energy yield • Generates large amounts of reduced coenzymes • Produces biosynthetic intermediates

27. Respiration • Transfer of electrons from electron acceptors to terminal electron acceptors • Aerobic organisms: oxygen • Anaerobic organisms: other inorganic compounds • Nitrate • Sulfate • Iron • Carbonate

28. Electron Transport System • Series of compounds which are alternatively reduced and oxidized • Orientation in the membrane. Net translocation of charge and hydrogen across the membrane

29. Chemiosmosis • Couples electron transport with ATP generation • Development of transmembrane potential by transfer of electrons and hydrogens • Where H+ reenters the cell, ATP synthease is present