Please answers part c and d. Briefly answer the questions below. A few sentences
ID: 539231 • Letter: P
Question
Please answers part c and d.
Briefly answer the questions below. A few sentences should be sufficient to fully answer each question. a) Briefly describe the Lock and Key model and explain why enzymes do not typically follow it. b) Briefly describe the composition, structure, and properties of silk. A complete answer will discuss its amino acid composition, structure, and how structure leads to silk's observed physical properties. c) Why is hydrogen bond formation NOT the primary driving force behind protein folding? d) CO_2 is an important allosteric regulator of hemoglobin. Describe in detail how CO_2 regulates hemoglobin function including details on how this regulator interacts with the protein. e) Write the reaction scheme demonstrating how an uncompetitive inhibitor affects a simple Michaelis-Menten enzymatic reaction. f) What is Levinthal's Paradox?Explanation / Answer
(a) The substate binds itself to the active site on the suface of the enzyme. The acive site on the enzyme is so designed that only a specific substrate can fit in it. Thisresults in the formation of an enzyme-substare complex (activated complex) which then decomposes to give the product and the enzyme is regenerated. Enzymes do not typically follow this mechanism because enzymes are realtively flexible molecules and as a result the active site undergoes continious remoulding by interaction with the substrate which results in an non-rigid enzyme-substrate complex.
(b) Two main proteins present in silk are sericin and fibroin. Fibroin is made up of amino acids Gly-Ser-Gly-Ala-Gly-Ala and forms beta pleated sheets, -keratin. In the beta pleated sheet structure the peptide chains are held together by intermolecular hydrogen bonding to form a flat sheet. These sheets are then stacked upon one another to form a 3D structure. Because of this structre silk is one of the strongest natural fibers and has a smooth, soft texture.
(c) Hydrophobic effect is the main driving force behind protein folding. Proteins have many hydrophobic amino acids. Water soluble proteins will consist of poar side chains which are directed towards water while the non-poar side chains are directed away from water and forms the hydrophobic part of the folded protein. This stabilizes the tertiary structure of protein. Thus minimizing the portion of hydrophobic part exposed to water is the main driving force behind protein folding.
(d) Hemoglobin exists in oxygenated state and deoxygenated state. When oxygen concentration is high the oxygenated state is favoured where as in cells where oxygen level are low the deoxygenated stae is favoured in order to facilitate maximum delivery of oxygen to the tissues. Hemoglobin's oxygen binding affinity is inversly realted to the acidity and CO2 concentration. As the tissues metabolic rate increses it produces more CO2 thereby decreasing the pH of blood. This decrease in pH promotes the dissociation of oxygen from hemoglobin. The enzyme carbonic anhydraze also plays an important role in decreasing the pH of blood.
(e)
(f) Theoretically speaking, unfolded protein chain have a large number of degrees of freedom. Because of this the number of possible conformations for a given protein is almost infinite and as a result the protein will take infinite time to arrive at its possible correct conformation. But in reality a protein can attain its correct conformation within a fraction of a second. This is known as Levinthal's paradox.