BIOL 101
Names: Lab 3-4 Post-Lab
Section:
Complete this post-lab assignment as a group
, in your own words. It is worth 15 pts.
Please type your answers after “Answer here:” for each question to maintain the formatting.
Decide which one
of you will bring a hard copy to lab next week to hand in for grading.
1.
(1 pts) Cells that are specialized to allow diffusion of substances from one place to another in the body, like those that line the air sacs (alveoli) of our lungs or that form the walls of our tiniest blood vessels (capillaries), are often broad and thin. Explain this observation, making specific reference to your results from Exercise 1
.
Answer here: 2.
(2 pts) Imagine we had included in Exercise 1 an agar rectangle that was 20 by 20 by 30 mm and you measured a rind thickness of 6 mm after soaking in NaOH for 2 minutes. Complete the table below for this cube. Surface
area
(cm
2
)
Volume
(cm
3
)
SA /
Volume
(cm
-1
)
Rind
thickness
(mm)
Uncolored
volume
(cm
3
)
Diffused
volume
(cm
3
)
Percent
diffused
(%) 3.
(2 pts) If you were to graph your group’s results for Exercise 1, would a bar graph or a scatter plot be the better choice? Why? Provide a complete graph title for this graph, considering the criteria for graph titles we discussed in Lab 1.
Answer here: 4.
(2 pts) Which of the three alternate hypotheses in Exercise 1 was most strongly supported? Explain why, with specific reference to your data
.
Answer here:
5.
(2 pts) What feature of dialysis tubing membrane makes it selectively permeable? Hint: see beginning of Exercise 2 in the lab manual. In Exercise 2, which solutes were able to diffuse freely through the dialysis tubing membrane and which could not? Answer here: 6.
(2 pts) The phospholipid bilayer of a biological membrane is impermeable to ions, polar molecules, and large molecules. Even water does not freely cross a phospholipid bilayer if aquaporin proteins are not present in the membrane. If you were to repeat Exercise 2 using a phospholipid bilayer membrane instead of dialysis tubing, how would the results have differed from your results using dialysis tubing? Hints: Iodine is an ionic solute, your textbook gives information on size and relevant properties of the other solutes involved. And consider your answer to the first part of question 5.
Answer here: 7.
(2 pts) The goal of the experiment in Part 2 was to determine the osmolarity of your plant tissue. Summarize the experimental design that you used to do this. Include which tuber you used, how you prepared them, the set-up of the experiment, and how you determined the osmolarity value. Answer here: 8.
(2 pts) Copy and paste the Excel graph of your group’s data here. Make sure to use the graphing checklist provided in Lab 1. Indicate the value on your graph that best indicates the osmolarity of both
tuber varieties studied by your group.
Answer here:
