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Chapter 6 An Introduction To Metabolism

Metabolism/Bioenergetics. Metabolism: The totality of an organism's chemical processes; managing the material and energy resources of the cellCatabolic pathways: degradative process such as cellular respiration; releases energyAnabolic pathways: building process such as protein synthesis; photosynthesis; consumes energy.

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Chapter 6 An Introduction To Metabolism

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    1. Chapter 6 An Introduction To Metabolism

    2. Metabolism/Bioenergetics Metabolism: The totality of an organism’s chemical processes; managing the material and energy resources of the cell Catabolic pathways: degradative process such as cellular respiration; releases energy Anabolic pathways: building process such as protein synthesis; photosynthesis; consumes energy

    3. Complexity of Metabolism

    4. Thermodynamics Energy (E)~ capacity to do work; Kinetic energy~ energy of motion; Potential energy~ stored energy Thermodynamics~ study of E transformations 1st Law: conservation of energy; E transferred/transformed, not created/destroyed 2nd Law: transformations increase entropy (disorder, randomness) quantity of E is constant, quality is not

    5. Stability, Spontaneous Change, Equilibrium and Work

    6. Free Energy Free energy: portion of system’s E that can perform work (at a constant T) Exergonic reaction: net release of free E to surroundings Endergonic reaction: absorbs free E from surroundings

    7. Free Energy Equation

    8. Significance of Free Energy

    9. Metabolic Disequilibrium

    10. Free Energy Gradient Keeps Metabolism away from Equilibrium

    11. Energy Coupling & ATP E coupling: use of exergonic process to drive an endergonic one (ATP) Adenosine triphosphate ATP tail: high negative charge ATP hydrolysis: release of free E Phosphorylation (phosphorylated intermediate)~ enzymes

    13. Energy Coupling by Phosphate Transfer

    14. The ATP Cycle

    15. Chemical Reactions

    16. An Energy Profile of a Reaction

    17. Enzymes Catalytic proteins: change the rate of reactions w/o being consumed Free E of activation (activation E): the E required to break bonds Substrate: enzyme reactant Active site: pocket or groove on enzyme that binds to substrate Induced fit model binding of substrate changes shape of the active site so that the substrate can bind

    18. Enzyme Properties

    20. The Catalytic Cycle of an Enzyme

    21. How an Enzyme Lowers Activation Energy Active site holds 2 or more reactants. Induced fit distorts bonds-less E required to break them. Active site may produce a micro-environment. Side chains of amino acids may participate.

    22. How Enzymes Work

    23. Initial Substrate Conc. Determines Rate of an Enzyme-Controlled Reaction

    24. Effects on Enzyme Activity Temperature pH Cofactors: inorganic, nonprotein helpers; e.g. zinc, iron, copper Coenzymes: organic helpers; e.g. vitamins

    25. Enzyme Inhibitors Irreversible (covalent); Reversible (weak bonds) Competitive: competes for active site (reversible); mimics the substrate Noncompetitive: bind to another part of enzyme (allosteric site) altering its conformation (shape); poisons, antibiotics

    26. Allosteric Regulation

    27. Allosteric Inhibition

    28. Feedback Inhibition

    29. Cooperativity

    30. Enzyme Catalysis Lab

    31. Each enzyme is specific for the reaction it will catalyze. In this laboratory, Enzyme = catalase Substrate = hydrogen peroxide (H2O2) Products = water and oxygen H2O2 H2O + O2

    32. To determine the amount of hydrogen peroxide that remains after the reaction, you will do a titration with KMnO4.

    34. Reading the Burette

    35. Analysis of Results Enzyme Action Over Time We can calculate the rate of a reaction by measuring, over time, either the disappearance of substrate or the appearance of product.

    36. Calculate the rate in moles/second between 40 and 50 seconds.

    37. After 40 seconds there were no more substrate molecules. The curve becomes flat at this point, and the rate is zero.

    40. Which of the following graphs represents the rate of the reaction shown above? Notice that in the graphs below, the y-axis is number of molecules/sec.

    41. What is the role of sulfuric acid (H2SO4) in this experiment?

    42. A student was performing a titration for this laboratory, and accidentally exceeded the endpoint. What would be the best step to obtain good data for this point?

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