enzymes - Cellular Metabolism Cellular s Energy as it...

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Unformatted text preview: Cellular Metabolism Cellular s Energy as it relates to Biology s s Energy for synthesis and movement Energy transformation s s Enzymes and how they speed reactions Metabolism and metabolic pathways s s Catabolism (ATP production) Anabolism (Synthesis of biologically important molecules) Energy in Biol. Systems: Energy s General definition of energy: General Capacity to do work Capacity s Chemical, transport, movement s s First Law of Thermodynamics: First Energy can neither be created nor destroyed nor Ultimate source of energy: Sun! 2 types of energy: Kinetic energy = motion examples ? Potential energy = stored energy examples ? Fig 4-2 Energy (E) Transfer Overview Energy Figure 4-1 Potential Energy heat (~ 70% of energy used in physical exercise) Kinetic Energy WORK Bioenergetics = Bioenergetics study of energy flow through biol. systems Chemical reactions transfer energy A+B Substrates or reactants C+D Products Speed of reaction = Reaction rate Initial force = Activation Energy Potential Energy Stored in Chemical Bonds of Substrate can be . . . Bonds 1. transferred to the chemical bonds of transferred the product the released as heat (usually waste) used to do work (= free energy) free 1. 1. Chemical Reactions s s s p 93 93 Activation energy Endergonic vs. exergonic reactions exergonic Coupled reactions Direct coupling vs. indirect coupling s Reversible vs. irreversible reactions Activation Energy Activation Fig 4-3 Endo- and Exergonic Reactions EndoWhich is which?? ATP + H2O ADP + Pi + H+ + Energy Enzyme (= Biol. Catalyst) Enzyme Some important characteristics of an enzyme: 1. 1. Enzymes are proteins ↑ rate of chemical reaction by lowering activation energy energy is not changed itself is not 1. 1. It may change DURING the reaction 1. does not change the nature of the reaction nor the does result result is specific 2. Fig 4-6 Enzymes lower activation energy: Enzymes All chemical reactions in body must be conducted at body temp.!! How do enzymes lower activation energy ? Enzymes bind to reactant molecules and bring them together in best position for rx. bring Some more characteristics of enzymes: enzymes: s s s s Usually end in –ase Inactive form: -ogen in few cases RNA has enzymatic in activity (eg: rRNA → peptide bond) Isoenzymes may be produced in different Isoenzymes areas of the body areas s E.g., LDH Active Site: Small region of the complex 3D structure is active (or binding) site. binding) Enzymes bind to substrate Old: Lock-and-key model / New: Induced-fit model Enzyme-substrate interaction: The old and the new model The Lock and Key: Induced fit: Enzyme Specificity Enzyme s Often: reaction with only one substrate reaction Sometimes: reaction with group of similar substrates similar s Naming of Enzymes Naming mostly suffix -ase mostly -ase first part gives info on function examples s s s s Kinase Phosphatase Peptidase Dehydrogenase Isoenzymes = different models of same enzyme (differ in 1 or few aa) enzyme Catalyze same reaction but under different conditions and in different tissues/organs conditions Examples: 1. 2. Amylase LDH → importance in diagnostics Enzyme Activity 1. 1. 1. 2. 1. 1. 2. depends on Proteolytic activation (for some) (for Cofactors & coenzymes (for some) (for Cofactors Temperature pH Other molecules interacting with enzyme Other interacting Competitive inhibitors Allosteric modulators 1) Proteolytic Activation Also 1. Pepsinogen 2. Trypsinogen Pepsin Trypsin 2) Cofactors & Coenzymes 2) structure: Inorganic molecules (?) function: conformational change of active site structure: Organic molecules (vitamin derivatives, FADH2 ....) function: act as receptors & carriers for atoms or functional groups that are removed from substrate Cofactors bind to active site 3) Breakage of intramolecular bonds lead to ? Siamese Siamese Cats Cats Tyrosine Tyrosine s tyrosinase tyrosinase Melanin Tyrosinase is temperature sensitive ⇒ does Tyrosinase not function at cat’s core body temperature (101.5° F) 3) 4) Molecules interacting with enzyme 4) Competitive inhibitors: bind to active site bind block active site Fig 4-13 E.g.: Penicillin binds covalently (= irreversibly to important bacterial enzyme active site) 4) Molecules interacting with enzyme, cont’d 4) Molecules Allosteric modulators (fig 4-14): bind to enzyme (fig away from active site change shape of away change active site (for better or for worse) active Special case: = end product inhibition Allosteric Modulation Reaction Rate Depends on Enzyme & Substrate Concentration Substrate Reversible Reactions follow the Law of Mass Action Law Three Major Types of Enzymatic Reactions: Reactions: 1. Oxydation - Reduction reactions (transfer of electrons or protons (H+)) Hydrolysis - Dehydration reactions Hydrolysis Dehydration (breakdown & synthesis of water) Addition-Subtraction-Exchange (of a Addition-Subtraction-Exchange functional group) reactions functional 1. 1. ? ...
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This note was uploaded on 03/17/2011 for the course BIO 202 taught by Professor Benking during the Spring '11 term at UT Chattanooga.

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