F BICH 410 1st Edition Lecture 13 Outline of Last Lecture Myoglobin Hemoglobin Outline of Current Lecture Hb T to R o 1st binding low affinity T o 2nd binding T to R o 3rd binding high affinity R o 4th high affinity R Cooperativity is designed to release O2 at low pressures Y pO2n p50n pO2n Allosteric effects binding of one site affects another site o Hb is allosteric quaternary protein o Homotropic ligand and effector identical o Heterotropic different o Binding of something that lowers O2 affinity increases p50 and moves curve to the rightT STATE o Binding of something that increases O2 affinity decreases p50 and moves curve to left R state o Bohr effect binding of O2 decreases proton binding o Bohr effect pka of ionizable groups in ionic interactions are perturbed specifically His146 DeoxyHb T state favors ionic interactions to form stable structure therefore protonated oxyHb R state O2 binds and ionic interactions disrupted deprotonated High H favors protonation favors T state lowers O2 affinity and increases p50 CO2 allosteric effector diminishes O2 binding decreasing pH and Hb acts as CO2 transporter Carbonic Anhydrase C02 H20 H HCO3o Carbonic anhydrase accelerates rxn o CO2 lowers the pH of blood o O2 depleted and muscles make lactic acid lowering pH o Consequently protons are taken up by Hb as O2 dissociates Carbamation Hb acts as CO2 transporter o HCO3 binds to amino N terminal group and forms carbamates o Aids in transport of CO2 to lungs o Increases Bohr effect by releasing H 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 o Carbamates form ion pairs and stabilize deoxy Allosteric shift to T release O2 co2 bpg h and shift to r state bind O2 02 favors R state and releases H causing equilibrium to CO2 to H20 SO c02 can be expired Hb releases 02 CO2 abundant pH low favors deoxy state BPG reason why O2 binds tighter to pure Hb than serum o Binds to central cavity of deoxyHb has 5 charge which interacts with positive charge amino acids in Hb Decreases O2 and pressure with altitude increases BPG production so increases O2 delivered to tissues Fetal Hb fetus receives O2 from mothers blood via placenta o Fetal blood has higher affinity for O2 than mother o HbF has composition alpha2gamma2 o HbF has lower affinity for BPG than HbA o Differences accounted for Ser 143 in place of His 143 in HbF
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