Consider the information provided in the Why? box and in Model 1 about these proteins.
a. In which body organ is pepsin active? b. In which body organ is pancreatic lipase active?
answer
a. The stomach b. the small intestine
question
For each enzyme in Model 1, circle the pH that best represents the environment in which the enzyme is most active.
answer
Pepsin 1.5 Lipase 8
question
Compare the rate of the pepsin-catalyzed reaction at pH 1.5 with the rate of the lipase-catalyzed
reaction at pH 1.5
answer
At 1.5, the pepsin-catalyzed reaction has already begun to react while the lipase-catalyzed reaction isn't able to work at such a low pH level.
question
Compare the rate of the pepsin-catalyzed reaction at pH 8 with the rate of the lipase-catalyzed reaction at pH 8.
answer
At 8, pepsin-catalyzed reaction isn't able to work because the enzymes have denatured while the lipase catalyzed reaction is able to react with ease.
question
Using your knowledge of protein structure, explain in detail the effect of exposing an enzyme to a pH outside of its optimal range. Include the effect on both enzyme structure and function.
answer
By exposing n enzyme to a pH outside of its range, the enzyme would denature which means that the enzyme will lose their structure and unfold.
question
At what pH values is lipase likely to be denatured? Justify your answer.
answer
Lipase looks to be denatured by the time it reaches a pH of 12. At 12, the reaction rate has gone down to zero.
question
At what pH values is pepsin likely to be denatured? Justify your answer
answer
Pepsin looks to be denatured by the time it reaches a pH of 5. At 5, the reaction rate has gone down to zero.
question
In addition to being produced in the pancreas, lipase is also produced in the stomach. Is the structure of pancreatic lipase the same as gastric (produced in the stomach) lipase? Justify your
reasoning.
answer
The structure would need to be different because the environment in the stomach is different from the pancreas, so the enzymes would have to change their structure in order to survive.
question
Antacids work by neutralizing acids, bringing the pH of the stomach to a range of 6—7. What is the effect of taking an antacid on a person's ability to digest proteins?
answer
This will slow down their ability to digest
question
Amylase is an enzyme that catalyzes the digestion of carbohydrates. The graphs in Model 2 provide data on several factors that affect the function of amylase in the body.
a. The relationship of which two variables is illustrated in graph A of Model 2?
answer
the rate of reaction and the temperature in °C
question
b. The relationship of which two variables is illustrated in graph B or Model 2?
answer
the rate of reaction and the enzyme concentration
question
c. The relationship of which two variables is illustrated in graph C or Model 2?
answer
the rate of reaction and the substrate concentration
question
What is the optimum temperature for amylase?
answer
37 °C
question
What is the biological significance of the temperature at which the amylase-catalyzed reaction is fastest?
answer
This is the temperature of the human body as well.
question
Predict what causes a decrease in enzyme activity at temperatures above 37 °C.
answer
The enzymes begin to denature.
question
A young child runs a fever of 40 °C for 24 hours. Explain what effect this may have on his digestion.
answer
With the addition of excessive heat, this can cause denaturing and decrease the activity of
the enzymes in the body that are breaking down things for energy.
question
Describe the relationship between enzyme concentration and reaction rate.
answer
the higher the enzyme concentration, the higher the rate of reaction.
question
Propose an explanation for this relationship
answer
Enzymes are catalysts. Catalysts lower the activation energy required for reactions. The lower the activation energy, the faster the rate. Therefore enzymes speed up reactions by lowering activation energy.
question
What is the relationship between substrate concentration and the reaction rate?
answer
the more substrate, the higher the reaction rate until the amount of the substrate exceeds the amount of the enzyme.
question
Propose an explanation for why a maximum reaction rate is reached in graph C.
answer
when all the active sites have been filled, the reaction rate levels off.
question
As a group, develop an analogy for the function of an enzyme that will explain the concentration graphs in Model 2 (graphs B and C)
answer
Enzymes are like builders. When the amount of building projects exceeds the amount available crews, the rate of new buildings built level off.
question
Would the reaction rate on graph B of Model 2 ever reach a maximum level? Justify your answer.
answer
The reaction rate of graph B could reach a maximum level if the enzyme concentration ever equaled the substrate concentration.
question
Predict why this bacterial polymerase is used instead of a human polymerase
answer
This bacterial polymerase is able to withstand extreme temperatures. If human polymerase were to be within such extreme thermal conditions, the enzyme would denature, rendering the entire operation faltered.
question
What would happen if you used a human polymerase in a series of PCR reactions?
answer
If a human polymerase were used within a series of PCRs, the enzyme affective to the according reactions would be denatured due to extreme temperatures.
question
As a group, develop an analogy for the function of an enzyme that will explain the concentration graphs in Model 2 (graphs B and C)
answer
Enzymes are like builders. When the amount of building projects exceeds the amount available crews, the rate of new buildings built level off.
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