enzymes PH/TEMP/Substrate Conc Flashcards
(12 cards)
Which of the following best describes the effect of temperature on enzyme activity?
b) Enzyme activity increases with temperature until an optimum, after which it rapidly decreases.
Why does a change in pH affect enzyme activity?
a) It changes the shape of the active site by disrupting hydrogen and ionic bonds.
What happens when substrate concentration increases beyond the saturation point?
b) The rate of reaction remains constant because all active sites are occupied.
Describe how temperature affects enzyme activity and explain why enzyme activity decreases at very high temperatures.
As temperature increases, enzyme activity increases due to more kinetic energy and more frequent successful collisions. However, above the optimum temperature, enzymes denature as bonds break, changing the shape of the active site, so the substrate no longer fits.
Explain how changing the pH of an enzyme-controlled reaction affects the enzyme’s ability to catalyze the reaction.
Changes in pH alter the charges on amino acids in the enzyme’s active site, affecting substrate binding. Extreme pH values break hydrogen and ionic bonds, denaturing the enzyme and decreasing activity.
Sketch a graph to show the effect of increasing substrate concentration on the rate of an enzyme-controlled reaction. Label the key points.
The graph should show a steep increase at first, leveling off at a plateau when active sites become saturated.
A student investigates the effect of temperature on enzyme activity. Explain why they should use a water bath to control the temperature.
A water bath maintains a constant temperature, ensuring results are reliable and not affected by fluctuations in room temperature.
A student carried out an experiment to measure the rate of an enzyme-catalyzed reaction at different pH levels. The following results were obtained: pH Rate of Reaction (arbitrary units) 3 1.2 5 3.8 7 5.6 9 3.2 11 0.8 a) Plot a graph of pH against the rate of reaction. b) Identify the optimum pH for this enzyme. c) Explain why the rate of reaction decreases at extreme pH values.
a) [Graph plotting pH on the x-axis and rate of reaction on the y-axis, showing a peak at pH 7.]
b) The optimum pH for this enzyme is 7.
c) Extreme pH values can alter the enzyme’s active site by disrupting hydrogen and ionic bonds, leading to denaturation and decreased activity.
An enzyme experiment was carried out at 20°C, 30°C, 40°C, and 50°C. The results showed that enzyme activity peaked at 37°C and then dropped sharply. Explain why enzyme activity decreases at 50°C.
At 50°C, the enzyme likely denatures due to the breaking of bonds that maintain its structure, altering the active site and reducing activity.
A student investigates the effect of substrate concentration on enzyme activity and obtains the following results: Substrate Concentration (%) Rate of Reaction (arbitrary units) 1 0.5 2 1.0 4 2.0 6 2.5 8 2.8 10 2.9 a) Plot a graph of substrate concentration against the rate of reaction. b) Explain the shape of the graph.
a) [Graph plotting substrate concentration on the x-axis and rate of reaction on the y-axis, showing a rapid increase followed by a plateau.]
b) Initially, as substrate concentration increases, the rate of reaction increases due to more frequent enzyme-substrate collisions. However, the rate levels off when enzymes become saturated, and additional substrate doesn’t increase the rate further.
