Assignment 4
Due September 19
Determining enzyme activity
Question 1. Multiple-choice
The mouse intestine was flushed before homogenization in order to:
Remove the enzyme maltase from the intestine
Remove the substrate maltose from the intestine
Remove blood from the intestine
Remove feces from the intestine
None of the above
Question 2. File upload
Use this simulated spectrophotometer to measure and record the absorption of each
solution. Then use a glucose standard curve to calculate amounts of glucose. Divide these
values by incubation time to complete the following table.
Tube
Incubation Absorption
Glucose
Maltase activity
number Time (min)
(ug)
(ug glucose/min)
1*
0
2
5
3
10
4
15
5
20
6
30
*This tube contains both homogenate and substrate, but was not incubated.
(TGO was added immediately after the substrate).
Make a line graph of glucose amount vs. incubation time using the on-line plotter.
Capture an image of the plotter, including both graph and plotter table, and submit it to
WebAssign.
Question 3. Refer to the data in the above table and do the following:
a) Record what you believe to be the most accurate value for maltase activity:
____ ug glucose/min
b) Discuss the question “Does enzyme activity depend on incubation time?” and give
sufficient details to justify your answer.
Properties of enzymes
Question 4. File upload
Use this simulated spectrophotometer to measure and record the absorption of each
solution.
Tube
number
Maltose
concentration
Absorption
of solutions
0
1
2
3
4
5
6
7
8
9
0
1.0
mM
2.5
mM
5.0
mM
10
mM
25
mM
50
mM
75
mM
100
mM
150
mM
0
Now use the on-line plotter to graph absorption vs. substrate concentration. Make a
scatter plot—if you want to add lines, make sure to connect the points (do not make a line
regression). Capture an image of the plotter, including both graph and plotter table, and
submit it to WebAssign.
Question 5. Essay
Think about the data in the above table and the shape of your graph. Then write a short
essay that answers the following questions:
What is the effect of substrate concentration on maltase activity? Explain why the shape
of your graph is not a straight line. (You have not been given the answer to this question,
so give the best explanation you can based on logic and information about enzymes on
the course web site.)
Question 6. File upload
Use the on-line plotter to construct a graph that displays the effect of pH on maltase
activity. Capture an image of the plotter, including both graph and plotter table, and
submit it to WebAssign.
Question 7. File upload
Use the on-line plotter to construct a graph that displays the effect of temperature on
maltase activity. Capture an image of the plotter, including both graph and plotter table,
and submit it to WebAssign.
Question 8. Multiple-choice
Based on the data in your graph, the pH optimum for maltase is:
A neutral pH
A slightly acidic pH
A slightly basic pH
A pH of 10
Maltase activity is the same at all pH values.
Question 9. Multiple-choice
Based on the temperature data in your graph, which of the following is a true statement?
Maltase has higher activity at 10°C than at 20°C.
Maltase has no activity at 4°C.
Maltase has no activity when the enzyme is boiled before assay.
The optimal temperature for maltase activity is 20°C.
All of these statements are true.
Question 10. File upload
Use the on-line plotter to construct a graph that displays the effect of copper ion on
maltase activity. Capture an image of the plotter, including both graph and plotter table,
and submit it to WebAssign.
Question 11. Multiple-choice
The concentration of copper ion that produces a 50% inhibition of maltase activity is
approximately:
0.1%
0.4%
2.0%
4.0%
10.0%
Applying what you have learned
Question 12. Matching
Complete the table, then answer the matching question in WebAssign.
Tube number
Correct label for
tubes (A-E)
1
2
3
4
5
Introduction to eukaryotic cells
Question 13. Essay
Observe the images and diagrams that compare cell and organelle sizes. Then write a
short essay that answers the following questions:
How do most prokaryotes compare in size to small and large eukaryotic cells?
How does a mitochondrion compare in size to a nucleus and to a prokaryote?
You might use statements such as “cell X is almost 20x bigger than cell Y” or you could
use this grid image to obtain measurements. Try to incorporate information from both the
images and the diagrams. Most importantly, your essay should make clear the magnitude
of size differences.
Question 14. Essay
View the videos in activity 3 and carefully observe the four living protists (two protists
are shown in video 1). Pick one protist from the first video and one protist from either of
the other videos and describe how each protist moves. Are visible structures involved in
locomotion? Also, describe any internal organelles that are clearly visible.
Question 15. Matching
Match each cell structure in the liver cell to its name, using the word bank below. Then
do the same matching in WebAssign. Note that several names are not used.
Name of structure or organelle
Structure A
Structure B
Structure C
Structure D
Structure E
mitochondrion, chloroplast, nucleus, nucleolus, Golgi, ribosomes, vesicles, plasma
membrane, cell wall