UTEP - Chem 3330 - Exam 2 - Chapter 5 Complete Questions With Accurate Answers

reversible binding of ligands is essential (T/F) T induced fit The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate. cooperativity A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits. Enzyme = _______ catalyst What do enzymes transform into other molecules? ligands ligand is called a substrate (T/F) F when dealing with enzymes What is the ligand binding site called? catalytic site or active site What is a ligand? a molecule that binds to a protein; typically a small molecule What is a binding site? a region in the protein where the ligand binds Ligand binds using different noncovalent interactions that dictate protein structure. (T/F) False - ligand binding uses the same noncovalent interactions found in protein structure When is a binding expressed in terms of partial pressure? when a ligand is a gas High specificity can be explained by the complementarity of the binding site and the ligand. There is complementarity in: _______ size, shape, charge, and hydrophobic/hydrophilic character Who founded the lock and key model? Emil Fisher; assumed that complementary surfaces are preformed. Explain Induced Fit induced fit allows for tighter binding of the ligand and high affinity for different ligands. Both the ligand and the protein can change their conformations. the ___ group is present in myoglobin. hemoglobin, and many other proteins designated heme proteins heme What does heme contain? heme consists of a complex organic ring structure, protoporphyrin with a bound iron atom in its ferrous state (Fe2+) What does His93 prevent? His93 prevents the simultaneous binding of more than one oxygen molecule with two free coordination sites which can result in irreversible conversion of Fe2+ to Fe3+ What color is deoxyhemoglobin? purple in venous blood What color is oxyhemoglobin? bright red in arterial blood How can affinity to oxygen change? What is it called? Must be a protein with multiple binding sites. Binding sites must be able to interact with each other called cooperativity. what is positive cooperativity? first binding event increases affinity at remaining sites and is recognized by sigmoidal binding curves (n 1) what is negative cooperativity? first binding event reduces affinity at remaining sites (n 1) Hill equation A mathematical expression for the degree of saturation of ligand binding to a molecule with multiple binding sites as a function of the ligand concentration allosteric regulation The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site. homotropic regulation when the substrate of an enzyme also regulates its activity (Ex: O2 is a homotropic allosteric modulator of Hb) heterotropic regulation different ligand affects binding of the normal ligand Tense state of hemoglobin more interactions, more stable, lower affinity for O2 Relaxed state of hemoglobin fewer interactions, more flexible, higher affinity for O2 What triggers a T to R conformational change? O2 binding Conformational change from the T state to the R state involves breaking ion pairs between the a1 - b2 interface (T/F) T What is one dramatic result of the T to R transition? the narrowing of the pocket between the B subunits What is the Bohr effect? a decrease in the amount of oxygen associated with hemoglobin in response to a lowered blood pH resulting from an increased concentration of carbon dioxide in the blood 15-20% of CO2 is exported in the form of a carbamate on the __________ of each of the polypeptide subunits amino terminal residues the carbamate forms additional __________, stabilizing the T state salt bridges 2,3-bisphosphoglycerate (BPG) - biproduct of metabolism - adjusts metabolism - in Hb - used for fine tuning oxygen transport - increased in high altitudes sickle cell anemia - Glu6 Val in the B chain of Hb - new Val side chain can bind to a different Hb molecule to form a strand similar to amyloidgenic proteins - this sickles (elongates) the red blood cells