Video Transcript
The graph provided shows the rate of an enzyme-controlled reaction relative to
temperature. How would you be able to determine an enzyme’s optimum temperature from a graph? (A) It is the temperature at which the reaction is completed. (B) It is always the first temperature recorded on the graph. (C) It is the temperature at which the rate of reaction is fastest. Or (D) it is the final temperature minus the temperature at which the rate of
reaction is slowest.
Enzymes are biological catalysts. They speed up chemical reactions but remain unchanged during this process. Enzymes are globular proteins. Each type of enzyme has a specific structure and shape. This includes a region called an active site, which is where the substrate molecule
will bind in order for the reaction to take place.
Since enzymes are proteins, they can be denatured by changing conditions, such as pH
and temperature. This means that the bonds holding the protein structure in place are disrupted, which
changes the shape of the active site. If the active site changes shape, the substrate can no longer fit. Therefore, the reaction can no longer be catalyzed by the enzyme.
Different enzymes have different optimum conditions. An enzyme will work best at a specific temperature and pH. As the graph shows, as the temperature increases, the rate of reaction also
increases. An increase in temperature increases the kinetic energy of both the enzyme and
substrate molecules. They move around more quickly, increasing the frequency of successful collisions,
thus increasing the rate of reaction.
The optimum temperature is the temperature at which an enzyme-controlled reaction
occurs at its highest rate. If we look at our graph, we can see that the rate of reaction increases as the
temperature increases up to 50 degrees Celsius. Above this temperature, the rate of reaction starts to decrease as the enzymes become
denatured.
We now have enough information to answer our question. The correct way to determine an enzyme’s optimum temperature from a graph is given in
answer choice (C). It is the temperature at which the rate of reaction is fastest.
