6. You have three unlabeled solutions-A, B, and C. You know that one is an enzym
ID: 212596 • Letter: 6
Question
6. You have three unlabeled solutions-A, B, and C. You know that one is an enzyme solution, another is a solution of that enzyme's substrate, and the third contains an inhibitor of enzyme activity. You know that when the enzyme and the substrate react, the solution will turn red. You mix various amounts of the three solutions. From the results, determine the identities of solutions A, B, and C. Is the inhibitor competitive or noncompetitive? Reaction Buffer (ml) Solution A (ml) Solution B (ml)Solution C (ml) Color 0.4 0.5 0.3 0.4 0.3 0.5 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Medium pink Red Light pink Colorless Dark pink Colorles:s Red 2 0.2 0.2 0.1 0.1 0.1 4 0.2 0.1 0.4 0.2Explanation / Answer
6.
When any of the two solutions are added, no reaction occurs (Tube #6 and 4). These tubes either lack the enzyme or substrate. Addition of B and C gives a red color (Tube 2), indicating a positive reaction. Hence, B and C will be either enzyme or substrate. Solution A is the inhibitor as a medium pink color is obtained only when this solution is added in equal concentration to mixture of solution B and C (tube 1)
When the inhibitor (Solution A) is added in high concentration (tube 3), it inhibits the reaction and give a light pink color. The light and medium pink color indicate level of inhibition of the enzyme catalyzed reaction. Thus, enzyme inhibition is dependent on concentration of inhibitor.
Increased amount of B (0.4 ml) and C (0.2 ml) is able to overcome the inhibition by the inhibitor A (Tube 7). Hence, the enzyme is now able to carry out the reaction completely and inhibitor has no effect on the binding of substrate to enzyme. However, increasing the concentration of solution B to 0.2 ml, while keeping solution C constant, is still able to overcome effects of the inhibitor A (Tube 5). Hence, the amount of color produced depends more on solution B than solution C.
Hence, solution B is substrate and solution C is enzyme. Fluctuating increasing levels of enzyme is able to overcome the effects of the inhibitor. Solution A is inhibitor.
In competitive inhibition, inhibitor has more affinity for enzyme than substrates. These inhibitors bind to the active site of the enzyme. Hence, they compete with the substrate for active site of enzyme.
In non-competitive inhibition, the inhibitor binds to enzyme at a site other than the active site of the enzyme. Thus, substrate and inhibitor can theoretically bind to the enzyme. Increasing substrate concentration will not increase rate of enzyme-catalyzed reaction or alter product formation. They reduce the number of functional enzyme molecules that are involved in the reaction.
Since the solution B can increased enzyme catalyzed reaction when doubled or even four time (tube 5 and 7), this type of inhibition is a competitive inhibition.
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