Question

1) Think about the bisubstrate reaction F + G -> H that can be catalyzed by an enzyme that 10) obeys Michaelis-Menten kinetics. Assume that [G] is so high that it is essentially unlimited.

Which one of the following scenarios is the one that can best be described as "first order with respect to F"?

=> [F] is three times lower than the Km.

Explain Why answer is [F] is three times lower than the Km.

14. Choose the answer and Explain Why
    If no ESI complex is ever formed, we can best conclude, based on our coverage of reversible 1inhibitors, that:

    1. A) the inhibitor is an uncompetitive inhibitor (but not the other two types)

    2. B) the inhibitor is a noncompetitive inhibitor (but not the other two types)

    3. C) the inhibitor could be either an uncompetitive or a noncompetitive inhibitor (but not the other type)

    4. D) the inhibitor is a competitive inhibitor (but not the other two types)

    5. E) the inhibitor could be either a competitive or an uncompetitive inhibitor (but not the other

       type)

Answer 1

Ans 1: Bi-substrate reactions are the ones in one enzyme catalyzes the conversion of two substrates into two products.
This kind of reaction can occur sequentially where one substrate binds first followed by the other substrate. After binding of both the substrate, the enzyme will convert them into products that are released one after another.
The other way by which these reactions occur is that initially it converts one substrate to a product during which enzyme gets modified followed by conversion of the second substrate into product.
According to the given reaction, F + G ----> H
It has said in the question that [G] is in unlimited concentration and to catalyze this reaction as 1st order, [F] has to be used in lower quantities than Km. This means when the concentration of F will be smaller than Km, it implies now the reaction rate depends on the [F] as it is in less quantity. When the rate of reaction depends on one substrate, then the order of the reaction will be the first order.
Ans 2: In competitive inhibition, the inhibitor binds to the active site where the substrate bind as an inhibitor resembles the substrate chemically. Only one component among the substrate or inhibitor can bind to the active site of an enzyme at a time. This means during competitive inhibition, no ESI complex will form.
In non-competitive inhibition, the inhibitor can bind to both free enzyme or substrate-bound enzyme as an inhibitor does not resemble substrate and bind to the site other than the active site. In this case, the ESI complex will form.
In uncompetitive inhibition, the inhibitor binds only to the Enzyme substrate complex and not to the free enzyme. Here also ESI complex will form.
If no ESI complex has formed that means it is the competitive inhibitor and not others like non-competitive and uncompetitive.
Hence, the correct option is :D the inhibitor is a competitive inhibitor (but not the other two types)

I hope this will help you.