The catalytic activity of an enzyme is being measured at pH 7.5 and requires that the side chain of a specific Cys (C) residue be in its unprotonated (conjugate base) form for the enzyme to be active. That specific Cys side chain in the protein has a pka of 7.8. a) For this Cys side chain with a pKa of 7.8, what is the base/acid ratio at pH 7.5? b) What fraction of the total enzyme molecules in a solution of the enzyme at pH 7.5 have that Cys side chain in the active form? (Express the answer as a %) c) The name of the Cys side chain functional group is? d) The active form of the Cys side chain in this enzyme would be? i. positively (+) charged ii. uncharged (neutral) iii. negatively (–) charged

The catalytic activity of an enzyme is being measured at pH 7.5 and requires that the side chain of a specific Cys (C) residue be in its unprotonated (conjugate base) form for the enzyme to be active. That specific Cys side chain in the protein has a pka of 7.8. a) For this Cys side chain with a pKa of 7.8, what is the base/acid ratio at pH 7.5? b) What fraction of the total enzyme molecules in a solution of the enzyme at pH 7.5 have that Cys side chain in the active form? (Express the answer as a %) c) The name of the Cys side chain functional group is? d) The active form of the Cys side chain in this enzyme would be? i. positively (+) charged ii. uncharged (neutral) iii. negatively (–) charged

Chemistry

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ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

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Spectroanalytical Methods

Spectroanalytical methods measure the wavelength and intensity of radiations that are either emitted or absorbed by a molecular or atomic species. These methods are useful for evaluating the electronic or atomic arrangement of the molecules of a given analyte.

Question

The catalytic activity of an enzyme is being measured at pH 7.5 and requires that the
side chain of a specific Cys (C) residue be in its unprotonated (conjugate base) form for
the enzyme to be active. That specific Cys side chain in the protein has a pKa of 7.8.
a) For this Cys side chain with a pKa of 7.8, what is the base/acid ratio at pH 7.5?
b) What fraction of the total enzyme molecules in a solution of the enzyme at pH 7.5
have that Cys side chain in the active form? (Express the answer as a %)
c) The name of the Cys side chain functional group is?
d) The active form of the Cys side chain in this enzyme would be?
i. positively (+) charged
ii. uncharged (neutral)
iii. negatively (–) charged

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