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20 Cards in this Set
- Front
- Back
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How do we prevent O2 from dissociating as a superoxide? |
Distal histidine |
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What's the diff. b/w hemoglobin and myoglobin? |
Hemoglobin is a homo-tetramer, myoglobin is a monomer |
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What formula do we use to determine ligand affinity? |
Fraction of protein bound by ligand =Y = [Ligand]/(Kd +[Ligand]) |
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What is the relationship between ([P] and [PL]) and (Kd and [L]) |
at 50% saturation [P] = [PL], and Kd = [L] |
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How do we make a hill plot? |
Linearize the hyperbolic plot of ligand affinity by taking the log of the ligand affinity formula |
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What is the linearized formula of ligand affinity? Aka what is the equation for a hill plot? |
Log (Y/1-Y) = nLog pO2 - nLog P50 Where, Y = mx + b and n=hill coefficient |
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What is the hill coefficient of a multisubunit complex where all the subunits express the same affinity for a ligand? |
N = 1 This is non-cooperative binding |
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Where n = hill coefficient; If n > 1, the binding shows ____ cooperativity If n < 1, the binding shows ____ cooperativity |
Positive, Negative |
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What are the two models of cooperativity? Which model contributes more? |
Two State, concerted --> Greater contributor One State, Seqeuntial
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What is the structural difference between oxy and deoxy hemoglobin? |
Fe 2+ is not in the plane of protoporphyrin in deoxyhemoglobin Fe 2+ is in the place of protoporphyrin in oxyhemoglobin |
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Describe the one state sequential "induced fit" model |
Binding of neighboring sites increases binding affinity without inducing a full conversion from T --> R |
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Describe the two state MWC model |
Overall assembly can only be in T or R state and binding of ligands shifts equilibrium between states As a hemoglobin tetramer binds each O2, the probability that the tetramer is in the R state increases |
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Where does the distal histidine bind? |
Binds to the oxygen that's at the 6th coordination site |
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Where does the proximal histidine bind? |
Binds 5th coordination site |
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What feature ensures the oxygen doesn't unbind as an ROS (superoxide)? |
Distal histidine |
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What does 2,3-BPG do? |
Lowers affinity of oxygen to hemoglobin by allostery |
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Where does BPG bind? |
Binds to middle of heterotetramer to 4 His and 2 Lys |
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What is the bohr effect? |
H+ ions and CO2 are allosteric effect that enhance oxygen release Lower pH decreases affinity of Oxygen |
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Where does carbamate bind to globins? |
CO2 binds with NH2 at N-terminus of globins |
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What does carbamate do? |
Triggers loss of O2 from hemoglobin |
