Bio 201 1st Edition Lecture 18 Outline of Last Lecture I. Last of Signal TransductionA. Receptor Tyrosine Kinases and RasB. Steroid Hormone ReceptorsOutline of Current Lecture. Spontaneous?. Catalysts. EnzymesA. Inducing FitB. How enzymes work1. Orientation2. Strain3. Chemistry C. Mutation and Human DiseasesCurrent Lecture. Spontaneous- Not all spontaneous reactions occur spontaneously. Consider DiamondCarbon, this reaction is exergonic but does not happen within the blink of an eye. This is because Activation energy needed to bring reactants to transition state is not low enough. II. Catalysts- Increase the reaction rate by altering transition state, thereby lowering Ea, altering intermediate. Catalysts do not alter reactants or products not G of reaction. Catalysts are not itself altered by reaction. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.III. Enzymes- Biological catalysts. Moste enzymes are proteins (some are RNA, ribozymes). Substrates bind to enzyme active site. Enzymes are specific for 1 or or small number of substrates. A. Inducing Fit- Binding of substrate to active site, this triggers conformational change in the enzyme that leads to catalytic activity (head hits pillow, pillow conforms to head shape), this is not a permanent change.B. How enzymes work1. Orientation- When an enzyme brings 2+ reactants close together and orients them so they can interact. 2. Strain- When an enzyme changes conformation, it may induce a strain on chemical bonds, facilitation hydrolysis. 3. Chemistry- When an enzyme interacts chemically with a substrate making the substrate more reactive.-The conformation and chemistry of the active site or critical for enzyme function. Induced fit model indicates that precision in the interaction between enzyme and substrate are moreimportant for enzyme activity. Enzymes are extremely sensitive to anything that alters their conformation.C. Mutation and Human Disease- Sir Archibald Garrod, in 1902, discovered mutations inenzymes homegentisic acid 1,2-dioxygenase can cause black urine disease. The absence of this enzyme caused black urine. -Most mutations do not directly affect active sites, active sites are sensitive to effects of changes elsewhere in protein. Enzyme activity is sensitive to temperature. -pH alters ionization of functional groups, pepsin- extracellular protease in stomach, pH=12. Chymotrypsin- extracellular protease in duodenum, pH=7.4. Arginase- catalyzes final step of the breakdown of ammonia into urea in liver
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