? asked in 科學及數學生物學 · 1 decade ago

Something about Oxygen Dissociation Curve

Q: The plateau of the curve indicates that a further increase in oxygen

pressure produce only a small increase in oxygen uptake. Why?

1 Answer

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  • 1 decade ago
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    Although I have no idea what experiment you are talking about, I guess it has something to do with using oxygen as a reactant, such as, respiration, maybe?

    OK. For a certain chemical reaction to go forward, the reaction rate is mainly dependent on a [limiting factor]. This factor can be the concentration of the one reactant, temperature, etc.

    So the question is: What makes that particular reactant to be limiting?

    Say you have A + B --> C. If the concentration of A equals B, you have optimal reaction rate, and neither A nor B is wasted in the reaction. However, if you have more A than B, the B will be used up in the reaction to make C. When no more B is left, the reaction stopped, even when there is still a lot of A. We can say that A is in excess. In this case, if you add more A, nothing happens. If you add more B, the reaction rate increase greatly because now both A and B are present. Therefore B is the limiting factor.

    In the first part of your experiment, oxygen was a limiting factor. Therefore by increasing the pressure of oxygen [=total amount of oxygen available to the reaction], the reaction rate increases. However, at a certain point, even if oxygen increase, the rate do not increase. Maybe now the oxygen is in excess. The other reactant becomes limiting factor.

    This second limiting factor maybe another reactant, or enzyme, or simply temperature.

    Source(s): f.5 chemistry
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