Lecture 3 â Enzymes Ecosystems ⢠Sunlight drives photosynthesis ...
Lecture 3 – Enzymes Ecosystems • Sunlight drives photosynthesis; sees the formation of plant material from CO2 • Herbivores act as an energy source for carnivores • Food eaten by animals is “burnt off” during respiration, providing energy for physical activity and growth • Photosynthesis (in chloroplasts) à Respiration (in mitochondria) à Photosynthesis Metabolism • Anabolism: The synthesis of complex molecules in cells (storage of energy) • Catabolism: The breakdown of food by heterotrophic metabolism in a number of stages (release of energy) • Autotrophic: Complex materials are built up from simple, inorganic materials using energy from sunlight (plants) • Heterotrophic: Metabolism in which the energy inherent in organic matter is released as organic compounds (respiration) (animals) • ATP (Adenosine Triphosphate): Major intracellular currency for the exchange of energy • ATP + H2O = Energy for cellular work
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Redox Reactions • Reduction/Oxidation processes (transfer of energy) • Oxidation: Addition of oxygen, removes hydrogen, loss of electrons, liberates energy • Reduction: Removes oxygen, addition of hydrogen, gaining of electrons, stores energy Free Energy • Each type of molecules has a certain level of internal energy • Chemical reactions are associated with a change in free energy • When the products of a reaction have a higher energy content (free energy), then energy has to be put into the system • When the reactants of a reaction have a lower energy content (free energy), they energy can be obtained from the system • Exothermic/Exergonic: Energy output (catabolic) • Endothermic/Endogonic: Energy input (anabolic) • Gibbs Free Energy: The energy change during a reaction (ΔG) • ΔG < 0: Exothermic reaction • ΔG > 0: Endothermic reaction • EA: Activation energy (energy required to activate a reaction) Activation Energy • Catalysts speed up the rate of a reaction • The catalysts used by living cells are the enzymes • Reduces the activation energy required Enzymes • Binding the substrate (reactants) to the surface of the enzyme at the enzyme’s active site • Lock and key model/induced fit model • Interactions between enzymes and substrates induces stress on particular bonds • Metal ions or other small organic molecules are called co-factors • More substrate; faster reaction • When substrate is in excess; the enzyme is saturated • Effected by temperature and pH
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Enzyme Inhibition • Competitive Inhibition: An inhibitor that mimics the substrate and competes for the active site • Non-Competitive Inhibition: An inhibitor binds to the enzyme and changes the shape of the active site Feedback • Allosteric Site: Another site of the enzyme, not the active site • Inhibitors feedback from end product of the reaction or metabolic pathways ATP/NAD • ATP + H2O ßà ADP + Pi ; ΔG = -30.5 kJmol-1 • NAD+ à NADH and NADP+ à NADPH • The reduced from of a number of biological molecules can be used as sources of energy to drive endothermic reactions • Very important in respiration • Is usually involved in oxidation reactions Lecture 4 – Respiration Stages in Catabolism • Glucose à Glycolysis à Krebs Cycle à Respiratory e- Transport Chain à 6CO2 + Energy
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Redox Reactions • Reduction/Oxidation processes (transfer of energy) • Oxidation: Addition of oxygen, removes hydrogen, loss of electrons, liberates energy • Reduction: Removes oxygen, addition of hydrogen, gaining of electrons, stores energy Free Energy • Each type of molecules has a certain level of internal energy • Chemical reactions are associated with a change in free energy • When the products of a reaction have a higher energy content (free energy), then energy has to be put into the system • When the reactants of a reaction have a lower energy content (free energy), they energy can be obtained from the system • Exothermic/Exergonic: Energy output (catabolic) • Endothermic/Endogonic: Energy input (anabolic) • Gibbs Free Energy: The energy change during a reaction (ΔG) • ΔG < 0: Exothermic reaction • ΔG > 0: Endothermic reaction • EA: Activation energy (energy required to activate a reaction) Activation Energy • Catalysts speed up the rate of a reaction • The catalysts used by living cells are the enzymes • Reduces the activation energy required Enzymes • Binding the substrate (reactants) to the surface of the enzyme at the enzyme’s active site • Lock and key model/induced fit model • Interactions between enzymes and substrates induces stress on particular bonds • Metal ions or other small organic molecules are called co-factors • More substrate; faster reaction • When substrate is in excess; the enzyme is saturated • Effected by temperature and pH
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Enzyme Inhibition • Competitive Inhibition: An inhibitor that mimics the substrate and competes for the active site • Non-Competitive Inhibition: An inhibitor binds to the enzyme and changes the shape of the active site Feedback • Allosteric Site: Another site of the enzyme, not the active site • Inhibitors feedback from end product of the reaction or metabolic pathways ATP/NAD • ATP + H2O ßà ADP + Pi ; ΔG = -30.5 kJmol-1 • NAD+ à NADH and NADP+ à NADPH • The reduced from of a number of biological molecules can be used as sources of energy to drive endothermic reactions • Very important in respiration • Is usually involved in oxidation reactions Lecture 4 – Respiration Stages in Catabolism • Glucose à Glycolysis à Krebs Cycle à Respiratory e- Transport Chain à 6CO2 + Energy
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