44. You found two enzymes that catalyze the same hydrolysis reaction in the same
ID: 142777 • Letter: 4
Question
44. You found two enzymes that catalyze the same hydrolysis reaction in the same substrate. You nalyzed their activities and obtained results shown in the graphs below. 1km- 1.0 microM, Vmax - 16.4 molisec Enzyme 82; Km- 20 microM, Vmax - 52 molisec so. 40.0 15.0 30.0 10.0 20.0 5.0 10.0 0.0 0.0 25 020406080100120 10 15 20 Substrate (micro M Substrate (micro M) Based on these results, which enzyme (Enzyme #1 or Enzyme #2) will be more effective at hydrolyzing the substrate in the following cells? Explain your reasoning with couple of sentences Cell Cell B: Contains-10 micro M of the substrates (4pts) oM of the substrates (4pts)Explanation / Answer
Km is the concentration of substrate which permits the enzyme to achieve half Vmax. An enzyme with a high Km has a low affinity for its substrate, and requires a greater concentration of substrate to achieve Vmax."
An enzyme with a low Km relative to the physiological concentration of substrate normally saturated with the substrate will act at a more or less constant rate, regardless of variations in the concentration of substrate within the physiological range.
An enzyme with a high Km relative to the physiological concentration of substrate is not normally saturated with substrate, and its activity will vary as the concentration of substrate varies so that the rate of formation of the product will depend on the availability of substrate.
Thus in the first graph shown above enzyme activity is independent of substrate owing to its low Km value and in the second graph enzyme activity is highly dependent on substrate concentration owing to its high Km value. Thus in the first graph enzyme will act at a more or less constant rate and in the second enzyme activity will vary as the concentration of substrate varies.
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