Question

Read each question carefully. Write your response in the space provided for each part of each question. Answers must be written out in paragraph form. Outlines, bulleted lists, or diagrams alone are not acceptable and will not be scored.

Enolase is an enzyme that catalyzes one reaction in glycolysis in all organisms that carry out this process. The amino acid sequence of enolase is similar but not identical in the organisms. Researchers purified enolase from  Saccharomyces cerevisiae, a single-celled eukaryotic yeast that grows best at  37°C, and from  Chloroflexus  aurantiacus, a bacterium that grows best at the much higher temperature of  55°C. The researchers compared the activity of purified enolase from the two organisms by measuring the rate of the reaction in the presence of varying concentrations of substrate and a constant amount of each enzyme at both  37°C and  55°C.

(a) Depending on the organism, the optimal  pH for enolase to catalyze its reaction is between  6.5 and  8.0.  Describe how a  pH below or above this range is likely to affect enolase and its catalytic ability.

(b)  Identify the appropriate negative control the researchers most likely used when measuring the reaction rate in the presence of each organism’s enolase.

(c) The researchers predict that for any particular concentration of substrate, the  C. aurantiacus enolase-catalyzed reaction is more rapid at  55°C than at  37°C. Provide reasoning to  justify the researchers’ prediction.

Answer 1

Answer:

a):

• pH below or above the optimal range will result in loss of the enzyme activity.
• Changing the pH above or below optimum range affect the charges that reside on the amino acid molecules.
• Amino acids present in the active site of enzymes that attracted each other may no longer continue to be attracted.
• Again, the shape of the active site of the enzyme will change as a result of which substrate binding will be affected.
• Overall we can say that the enzymes are denatured.

b):

• The negative control that the researchers are most likely to use when measuring the reaction rate in the presence of each organism’s enolase is control with no enzyme.

c):

• Since the C.aurantiacus grows best at 550C , we can say that the enzymes that they produce must be at this temperature and so they must be sensitive to this temperature ; hence they would show more activity at 550C temperature.

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