A) Write the Henderson-Hasselbalch equation for the acid dissociation reaction of guanine. Identify the conjugate acid and conjugate base (HA and A-) for guanine forms. B) If the pK₂=9.7 (see above), What is the value of the acid dissociation equilibrium K₂? C) At pH 7.4, calculate (1) the ratio of the protonated and deprotonated forms of guanine. (2) the fraction of protonated guanine (i.e., HA / (HA+ A-)
Catalysis and Enzymatic Reactions
Catalysis is the kind of chemical reaction in which the rate (speed) of a reaction is enhanced by the catalyst which is not consumed during the process of reaction and afterward it is removed when the catalyst is not used to make up the impurity in the product. The enzymatic reaction is the reaction that is catalyzed via enzymes.
Lock And Key Model
The lock-and-key model is used to describe the catalytic enzyme activity, based on the interaction between enzyme and substrate. This model considers the lock as an enzyme and the key as a substrate to explain this model. The concept of how a unique distinct key only can have the access to open a particular lock resembles how the specific substrate can only fit into the particular active site of the enzyme. This is significant in understanding the intermolecular interaction between proteins and plays a vital role in drug interaction.
![cids and bases. Guanine is weakly acidic. It can lose a proton at higher pH, which disrupts base pairing and DNA
structure. (See section 1.3 of your textbook and the lecture slides.)
SACZALLAES
H
Guanine (G)
Biochemistry P14
Seventh Edition
2012 W. H. Freeman and Company
NH₂
pk₂=9.7
H
+H*
NH₂
1.0
0.8
0.6
E
0.4-
0.2
0
Fraction of molecules in
double-helical form
gure 1.16
8
9
pH
10
11
A) Write the Henderson-Hasselbalch equation for the acid dissociation reaction of guanine. Identify the conjugate acid
and conjugate base (HA and A-) for guanine forms.
B) If the pK₂=9.7 (see above), What is the value of the acid dissociation equilibrium Ka?
C)
At pH 7.4, calculate (1) the ratio of the protonated and deprotonated forms of guanine. (2) the fraction of
protonated guanine (i.e., HA / (HA+ A-)
D) The titration curve above shows DNA being titrated with a strong base, such as NaOH. Calculate the precise
fraction of DNA in the double helical form at three different pH values: 7.4, 8.4, and 9.4. [Hint: Note that the
double-helical form requires the protonation of guanine. Therefore, you will need to calculate the fraction in part C
(above).]](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F98f55b86-7303-4c60-8f43-d1d4ebde1187%2F52eddad2-8963-443c-8e92-3bac845ec4c3%2Fid5ofm_processed.jpeg&w=3840&q=75)
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