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NOT be graded. Page 3 Question #1 (Tutorial and Lecture, 18 points)
The enzyme carbonic anhydrase of erythrocytes catalyzes the hydration of CO2:
H2O + CO2 H2CO3 This reaction is important in the transport of CO2 from the tissues to the lungs.
Carbonic anhydrase is a monomeric enzyme with a molecular mass of 30, 000 Daltons.
(a) Provide the 1 word (semi) systematic name for the enzyme ____________________ (2 points).
(b) (2 points) The kcat for the enzyme (pH = 7.4) is 1.5 x 105 sec-1. State in a single sentence what
a kcat value of 1.5 x 105 sec-1 means. ( c) A series of enzyme assays was carried out with an unknown quantity of carbonic anhydrase. The data
was subjected to a Lineweaver-Burk analysis and the following results were obtained
Slope of line, m = 1.5 min/L.
Intercept on y-axis, b = 0.17 (mmol/min)-1
(i) (5 points) What quantity of carbonic anhydrase (in µ g) was used in the enzyme assays? Page 4 (ii) (2 points) Calculate Km. Express your answer in mM. (iii) (2 points) Using the concepts of active site filling and maximum reaction rate, explain in 2-3 sentences
what a Km value represents. (d) Carbonic anhydrase is inhibited by acetazolamide, a drug used to treat glaucoma (high pressure within the
eyeball). The experimental curve of reaction velocity, given here as percentage of Vmax versus [S, units not
shown] for the carbonic anhydrase reaction (+/-acetazolamide) is illustrated (Note: the same enzyme
concentration was used in both cases). (i) (1 point) Is the data consistent with the idea that the inhibitor reversibly binds in the active site
Yes or No? (Circle one)
(ii) (4 points) Briefly explain your answer to (i). Begin your answer in the space next to the graph. Page 5 Question #2 (20 points)
In some microorganisms, enzymes called peptide synthetases catalyze the formation of peptide bonds without
the participation of ribosomes, tRNA, mRNA etc. The formation of the peptide bond between the two amino
acids involves the consumption of ATP. Consider the specific case of peptide bond formation between two
Glycine + Glycine + ATP Glycylglycine + AMP + PPi + H+ (a) (5 points) Calculate the threshold amount of energy that must be supplied to synthesize 1 mol of
glycylglycine by the following mechanism .
2 Glycine Glycylglycine +...
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This test prep was uploaded on 04/01/2014 for the course BIOL 201 taught by Professor Chowrira during the Winter '13 term at The University of British Columbia.
- Winter '13