Question

1. Carbonic anhydrase is an enzyme that willconvert CO2 and water into HCO3.

CO2 + H20 > H+ + HCO3

Assume the Km of one variant of carbonicanhydrase is 1 mM.

First, imagine an experiment employing 10 testtubes. The test tubes are all filled with 100 ml water. Imaginethat the different test tubes have different concentrations of CO2,ranging from 0.01 mM to 100 mM CO2. Initially, there isNO enzyme in any of the test tubes.

(a) Draw a graph showing what you might expectto see for the amount of HCO3 in each of the test tubes 1 minuteafter the addition of CO2. Be sure to label the axes of the graph.Designate this curve as %u201CA%u201D (note: the exact values onthe Y axes here are guestimates %u2013 you get to make them up). (4points)

(b) Now, imagine that the test tubes arefilled with water and a significant amount (say, 1 mM) of theenzyme carbonic anhydrase in each test tube. Draw on the same graphas before what you might expect to see for the amount of HCO3 ineach of the test tubes 1 minute after the addition of CO2. Labelthis curve %u201CB%u201D. (note: again, the exact values on the Yaxes here are guestimates %u2013 you get to make them up). (2points)

(c) Now, on the same plot, draw a graphshowing the curve that results when you subtract the data obtainedin the first condition (without enzyme) from the data obtained inthe experiments obtained when the enzyme is present. Label this curve %u201CC%u201D. (2 points)

4. Using the data from 2C above (that is, subtracting thebackground production of CO2 due to simple mass action from thatresulting from the combination of enzyme action and mass action),draw a graph showing the alteration in the rate of carbonicanhydrase as the CO2 level is varied as a percentage of the maximal rateof HCO3 production %u2013 that is, 100% is as fast as the enzymecan function. Be sure to label the axes of the graphs. That is,again draw a graph showing what you might expect to see for theamount of HCO3 produced by the action of the enzyme in each of thetest tubes 1 minute after the addition of CO2. (4 points)

There are many different isoforms of thisenzyme (see for instance

http://en.wikipedia.org/wiki/Carbonic_anhydrase

Assume that one variant has a Km of 10 mM.Draw on the same graph as above a plot showing the alteration inthe rate of carbonic anhydrase as the CO2 level is varied, assumingthe concentration of the enzyme (1 mM) in the test tube is the sameas for the previous enzyme. (2 points)