SC BIOL 541 - Molecular Basis of Hemoglobin (3 pages)

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Molecular Basis of Hemoglobin

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Molecular Basis of Hemoglobin


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University Of South Carolina-Columbia
Biol 541 - Biochemistry

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BIOL 541 1ST Edition Lecture 7 Outline of Last Lecture I Extract Crystallography Outline of Current Lecture II Positive Co operativity III Bohr effect IV Enzymes Kinetics Current Lecture Biochemistry Lecture 7 Molecular basis for hemoglobin properties Positive co operativity Oxygen binding on one subunit alters the conformation for other units to accept oxygen readily This coordinated activity enables bonds to have a low energy state in oxygenated as well as deoxygenated states 1 ASP Asparatic acid H bond 2 GLU THR H bond Oxygen binding Oxygen displaces HIS and donates 2 unpaired electrons to Fe 4 unpaired electrons Thus combine to form 3 pairs of electrons Low spin state of electrons creates less spin radius shrinks Deoxygenated state Radius large Fe can not move into the ring Oxygenated state Radius small Fe moves into the ring Fe is attached to HIS in the helix and pulls HIS The F helix is pulled to hemoglobin In turn the bonds stabilizing elbow fulcrum amplifies the tip 6 10 A HIS moves but the elbow moves a full 1 A 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 Loops 90 degrees rotated to the right and make a connection to the sub units in the deoxygenated form Unstable low state forms the formation of the bonds drives energy for change in conformation for alpha unit Exposing Fe to any oxygen and moving F helix not all the way to the center but exposed Kinetically and mechanically molecular affinity for oxygen increases as Fe is closer Oxygen binds to Beta unit and forces alpha unit into the oxygenated conformation More Fe becomes available and increases alpha unit s availability for Fe Bohr Effect Sensitivity of Hb hemoglobin to pH HIS is a pH sensor HIS charged when forms an ionic bond when the c o of the asparatic acid HIS is not charged in its physiological environment As asparatic acid increases pka to 3 pH decreases to 7 2 and protonates the

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