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Cooperativity

by Kevin Ahern, PhD
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    Now, I'm going to show you schematically here what actually happens with that process I've just described to you. Hemoglobin can exist in what are called "two states". A T-state, which is described as the tight state and R-state, which is described as the relax state. And on this figure, the T-state is shown in squares and the R-state is shown as circles. Well, what's the difference between the two? The difference is that the T-state does not tend to bind oxygen very well at all. Whereas the R-state binds oxygen really well. What happens when hemoglobin gets to the lungs if it's in the T-state? It's in state that we see on the left. Four units, none of which like to bind oxygen very well. Well, the oxygen concentration in the lungs is relatively high. In fact, it's very high compared to what it was in the rest of the body. It's so high, in fact, that oxygen forces its way onto one of those units that doesn’t want to bind oxygen. Well, that's depicted in the second figure over. We see the blue circular form. That is that molecule or that protein of globin that got changed in structure by the binding of the first oxygen. So that change in structure changed it from a T-state into an R-state. And we can see that as a result of that change, that blue circle is interacting with two other subunits. And those two other subunits have started to change their shape, meaning that the change in shape of the first one has been communicated to the other two subunits touching it. Well, because they have had their shape changed slightly, each of those subunits is more like an R than it was like a T. The result being that...

    About the Lecture

    The lecture Cooperativity by Kevin Ahern, PhD is from the course Amino Acid Metabolism.


    Included Quiz Questions

    1. The binding of the first oxygen is the least favorable oxygen binding.
    2. The binding of the last oxygen is the least favorable oxygen binding.
    3. The binding of oxygen turns hemoglobin into the T-state.
    4. None of the answers are true.
    5. All of the answers are true.
    1. None of the answers are true.
    2. ...to the same extent as hemoglobin at high oxygen concentration and at very low.
    3. ...with high affinity at low and high concentrations.
    4. ...oxygen concentration.
    5. ...non-cooperatively.

    Author of lecture Cooperativity

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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