Hemoglobin & Myoglobin

Will be realesed and his has a pka of 66 the same his

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Unformatted text preview: with one the reaction will go a lot faster - want to know how the proton and CO2 - how they are going to promot the release of oxygen from hemoglobin? MCB 2000 Lecture 6 23 BGP - carbon and protons stablize the T state - all shift to the right - look at 50% staturation - - the lower the number of PO2 the hgiher the affi nity of hemoglobin for oxygen - shifting right wards the numbers of incrases - the affi nity for oxygen is decrease (being release to the tissue) Hb carries 2 end products of respiration: Binding of O2 to Hb influenced by pH and [CO2] Lower pH and a lot of CO2 r elease of oxygen (88% r elase) - more r ealse. muslce aerobic - gets ATP from aerobic r espiration 2/8 and 2/11/13 drop of pH - greater release of oxygen from hemoglobin - favor the relase of oxygen from hemoglbin MCB 2000 Lecture 6 Drop of pH will relase an additionally 11% - this makes s ense because excersiting tissue - the PP drops to about 20 torr Bohr Effect: Chemistry of H+ Binding In the lungs where hemolgobin loaded with oxygen - proton no longer going to be bound to salt bridge - the proton will be realesed and His has a pka of 6.6 - the same His residue dealing wtih low PP of oxygen - the His will act as a base - but in the lungs His will act as an acid Protons react with Histidine side chains. His-146 in B-subunit important; protonation promotes release of O2. Acid-base properties of Hb Where is the proton binding? - how do a proton effect the relase of oxygen from hemoglobin? one of the salt briges: His 146 and Asp 94 - when you have a proton in s olution - its going to be added to the His ( pka around 6) and act as a base or acid the end products going to be added to His and reestablish the salt bridge with Asp 94 when oxygen is realease - promopts this r elase is reforming the salt bridge that was broken -- His 146 becomes protonated then reform salt bridge - His in capillary beds is going to have a pka of 8.2 not 6 and that means it (the higher the pka) the greater tendency to accept a proton pKa of His146 = 6.6 for oxygenated Hb; pKa of His146 = 8.2 in deoxygenated Hb 2/8 and 2/11/13 MCB 2000 Lecture 6 News: the fi rst thing when trying to dig out your car and you start it up - you have to clear your ex. - if not will fi ll up with CO2 - fi rst looks like a c old or fl u - put him in hyperbaric chambers - to recover from CO2 posioning - binds to hemoblogin much more tightly then oxygen does - now oxygen cant be released - why was he put in the chamber? - raise the PPo2 and out heat the CO2 The Bohr Effect: Chemistry of [CO2]*binding At low pH and high CO2 in peripheral tissues, Hb affinity for O2 decreases. CO2 binds to -amino group at amino terminus of each globin chain Amino terminus becomes an anion reacts with Arg141 of -chain; forms a salt bridge Deoxygenated (T) state stabilized and promotes release of O2 2/8 and 2/11/13 CO2 combine wtih water forms carbonic acid and dissoicates into bicarbonate and the proton - in addition to the weak organic acid - will relase protons into the blood stream - leads to the release of the proton - CO2 going to bind to the free amino terminus - free amino terminus - form c arbamate - and liberate a proton - now have an added proton and CO2 has two effects - alter M and that process a proton and binds to hemogloin - making carbamte - and that bicarbonate equil. CB 2000 Lecture 6 makes a proton - this ensure that oxygen relase from the tissue </99"2()%*[3435(1-*$9*!'* The deliverly of oxygen to tissues is also tied into the buffering capacity of hemoglobin - hemoglobin has accpeted a proton - in capillary co2 with water to form carboniacic acid and the bicarbonate can go into the blood stream - in the lungs (CO2 as gas - has you exhale you effect the direction of the equilbria) - rate of breathing tied into the pH - low pH - going to signal the rest of the body to (increase the breathing - release more CO2 - exhale more and this willl allow the blood to become more alloic - hold your breath - blood pH will decrease bcecause not exhaling the CO2 pKa of H2CO3 = 6.35; blood pH = 7.4; therefore ~90% of dissolved CO2 will be this above is sensed by hypothamlus of the brain and - regulates this present as HCO3 and H+. 2/8 and 2/11/13 MCB 2000 Lecture 6...
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