Download 8 Factors Affecting the Rate of Enzyme Activity NOTES I. Pepsin a

Factors Affecting the Rate of Enzyme Activity
NOTES
I. Pepsin
a) Pepsin is an _________________ released in the _________________ that breaks down the ______________
in food into its ____________________________ building blocks.
b) Diagram:
Pepsin
c) Pepsin will ONLY break down the _________________ in food, and not organic compounds like
_____________________ and __________. This is because protein has a specific _______________ that fits
perfectly into the pepsin enzyme.
II. RATE of Enzyme Activity
The rate (speed) at which all enzymes in the body – like pepsin in the stomach – work depends on TWO factors:
(1) Temperature
1. As
temperature
rises, enzyme
activity speeds
up
2. Optimum (best)
temperature
3. Enzyme stops working because it begins to lose its _________________
Almost ALL enzymes work best at ______________ temperature, which is _________, or ___________.
This is why it is important that we maintain temperature ___________________, or a stable body temperature.
(2) pH
•
•
pH is a measure of how _______________ or basic a substance is
Most enzymes work best at a pH of approximately __________, which is the pH of the blood.
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I. How does TEMPERATURE affect the RATE at which pepsin works?
The effect of temperature on the action of pepsin, a protein-digesting enzyme present in stomach fluid,
was tested. In this investigation, 20 milliliters of stomach fluid and 10 grams of protein were placed in each of five
test tubes. The tubes were then kept at different temperatures. After 24 hours, the contents of each tube were
tested to determine the amount of protein that had been digested. The results are shown in the table below.
Using the information in the data table, construct a line graph on the grid, following the directions below.
1. Mark an appropriate scale on each axis.
2. Plot the data on the grid. Surround each point with a small circle and connect the points.
3. According to your graph, at what
temperature does pepsin work the fastest?
_______________
4. What happens to pepsin activity at really
low temperatures and really high
temperatures?
_________________________________
_________________________________
5. Our normal body temperature is 98.6°F (37°C). How does this graph show why it is important to maintain
temperature homeostasis (a stable body temperature)? What do you think happens to the speed of enzyme
activity when you have a fever?
_________________________________________________________________________________________
_________________________________________________________________________________________
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_________________________________________________________________________________________
II. How does pH affect the RATE at which pepsin works?
a) The pH of a substance is a measurement of how acidic the substance is, or how much acid is in the substance.
b) When you measure the pH of a substance, the measurement is a number between 1 and 14.
pH of substance
Acid or Base?
Example
Between 0 and 7.0
7.0
Between 7.0 and 14.0
•
The lower the pH of a substance, the more _________________ the substance is.
•
The higher the pH of a substance, the more _________________ the substance is.
•
The pH of our blood is approximately ____________.
c) The graph below shows the rate (speed) at which pepsin and another enzyme (trypsin, found in the small intestine)
work at different pHs:
(5) Based on the information above, what do you think the
pH in our stomachs must be?
Pepsin:
(1) At what pH does pepsin work the fastest? _______
________________________
(2) Does pepsin work best in acid or in base? ________
(6) What would happen if this pH did not remain stable?
Trypsin:
___________________________________________
(3) At what pH does trypsin work the fastest? _______
(4) Does trypsin work best in acid or in base? ________
___________________________________________
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___________________________________________
Enzymes
REGENTS PRACTICE
(4) the temperature before the reaction occurs
1. Meat tenderizer contains an enzyme that interacts with
meat. If meat is coated with tenderizer and then placed in a
refrigerator for a short time, how would the enzyme be
affected?
(1)
(2)
(3)
(4)
5. The graph below shows the affect of temperature on the
relative rate of action of enzyme X on a protein.
It would be broken down.
Its activity would slow down.
Its shape would change.
It would no longer act as an enzyme.
2. Which condition is necessary for enzymes to function
properly in the human body?
(1)
(2)
(3)
(4)
These chemicals must have a specific shape.
These chemicals must be able to replicate.
Body temperature must be above 40°C.
Body pH must be above 10.
Which change would not affect the relative rate of action of
enzyme X?
3. The graph below illustrates the relative amounts of
product formed by the action of an enzyme in a solution with
a pH of 6 at seven different temperatures.
(1) the addition of cold water when the reaction is at
50°C
(2) an increase in temperature from 70°C to 80°C
(3) the removal of the protein when the reaction is at
30°C
(4) a decrease in temperature from 40°C to 10°C
6. The diagram below represents a beaker containing a
solution of various molecules involved in digestion.
Which statement best expresses the amount of product that
will be formed at each temperature if the experiment is
repeated at a pH of 4?
(1) The amount of product formed will be equal to that
produced at pH 6.
(2) The amount of product formed will be greater than
that produced at pH 6.
(3) The amount of product formed will be less than that
produced at pH 6.
(4) The amount of product formed can not be accurately
predicted.
Which structures represent products of digestion?
(1) A and D
(2) B and C
(3) B and E
(4) D and E
7. An enzyme and four different molecules are shown in the
diagram below.
4. The equation below represents a chemical reaction that
occurs in humans.
What data should be collected to support the hypothesis that
enzyme C works best in an environment that is slightly basic?
(1) the shape of enzyme C
(2) the amount of substance W produced in five minutes
at various pH levels
(3) the shapes of substances X and Y after the reaction
occurs
The enzyme would most likely affect reactions involving
(1) molecule A, only
(2) molecule C, only
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(3) molecules B and D
(4) molecules A and C
Base your answers to questions 8 and 9 on the graph below
and on your knowledge of biology.
8. Pepsin works best in which type of environment?
(1)
(2)
(3)
(4)
acidic, only
basic, only
neutral
sometimes acidic, sometimes basic
9. Neither enzyme works at a pH of
(1) 1
(2) 5
(3) 3
(4) 4
10. An incomplete graph is shown below:
What label could appropriately be used to replace letter Z on the axis?
Base your answers to questions 11 and 12 on the statement below and on your knowledge of biology:
Some internal environmental factors may interfere with the ability of an enzyme to function efficiently.
11. Identify two internal environment factors that directly influence the rate of enzyme action.
_________________________________________________________________________________________________
_________________________________________________________________________________________________
12. Explain why changing the shape of an enzyme could affect the ability of the enzyme to function.
_________________________________________________________________________________________________
_________________________________________________________________________________________________
13. Enzyme molecules are affected by changes in conditions within organisms. Explain how a prolonged, excessively high body
temperature during an illness could be fatal to humans.
_________________________________________________________________________________________________
_________________________________________________________________________________________________
_________________________________________________________________________________________________
_________________________________________________________________________________________________
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