Osmosis and the Marvelous Egg

A Report on Ongoing First Year Biology Lab Development

Richard Cooper, Department of Mathematics

Robert Blystone, Department of Biology

For Synergistic Learning In Biology and Statistics (SLIBS)

A Look at the Problem.

As a first lab for the developmental biology course we decided to try the lab suggested by Barbara Cocanour and Alease Bruce in "Osmosis and The Marvelous Membrane" JCST November 1985, pp127-130. This serves four purposes:

To introduce the biology students to data collection, storage and analysis in a manner that is not intimidating.
To prepare the biology students for handling the eggs in preparation for the embryo lab which is the second lab.
To introduce the biology students to the concept of osmosis in anticipation of the red blood cell lab later in the semester.
To introduce the biology students to the concept and style of the lab report.

We weighed and decalcified six eggs by soaking them in an acetic acid solution for 48 hours.

We weighed and decalcified six eggs by soaking them in an acetic acid solution for 24 hours. Removing the eggs from the acetic acid, dying them, weighing them and soaking them in a new acetic acid solution for an additional 24 hours.

We decalcified an additional eight eggs by soaking them in an acetic acid solution for 48 hour.

We then placed the 20 eggs in beakers of de-ionized water. At fifteen minute intervals we removed the eggs (one at a time), dried the egg, recorded its weight and returned it to the beaker.

The Raw Data

Time	Egg1	Egg2	Egg3	Egg4	Egg5	Egg6
Whole	51.26	51.99	51.11	47.43	49.98	52.37
DeShell	74.71	82.84	72.6	70.83	70.64	76.4
15	76.08	84.58	74.17	72.58	71.78	77.97
30	77.24	86.02	75.8	73.86	72.62	79.01
45	77.79	86.67	75.84	74.55	73.11	79.59
60	78.18	87.12	76.17	74.88	73.46	79.9
75	78.58	87.69	76.55	75.34	73.91	80.34
90	78.75	Burst	76.86	75.66	74.09	80.58
105	78.91		76.98	75.7	74.21	80.69
120	78.94		77.03	75.75	74.28	80.6

This is what the data looks like after dividing by the weight of the decalcified egg:

Time	Egg1	Egg3	Egg4	Egg5	Egg6
0	1.0000	1.0000	1.0000	1.0000	1.0000
15	1.0183	1.0216	1.0247	1.0161	1.0205
30	1.0339	1.0441	1.0428	1.0280	1.0342
45	1.0412	1.0446	1.0525	1.0350	1.0418
60	1.0464	1.0492	1.0572	1.0399	1.0458
75	1.0518	1.0544	1.0637	1.0463	1.0516
90	1.0541	1.0587	1.0682	1.0488	1.0547
105	1.0562	1.0603	1.0688	1.0505	1.0562
120	1.0566	1.0610	1.0695	1.0515	1.0550

A look at differences:

Time	Egg1	1st Diff	2nd Diff	3rd Diff	4th Diff
0	1.0000	0.0183	-0.0028	-0.0054	0.0114
15	1.0183	0.0155	-0.0082	0.0060	-0.0037
30	1.0339	0.0074	-0.0021	0.0023	-0.0055
45	1.0412	0.0052	0.0001	-0.0032	0.0062
60	1.0464	0.0054	-0.0031	0.0029	-0.0046
75	1.0518	0.0023	-0.0001	-0.0016
90	1.0541	0.0021	-0.0017
105	1.0562	0.0004
120	1.0566

A look at differences over weight at time 0:

Time	Egg1	diff/weight
0	74.71	0.0183
15	76.08	0.0152
30	77.24	0.0071
45	77.79	0.0050
60	78.18	0.0051
75	78.58	0.0022
90	78.75	0.0020
105	78.91	0.0004
120	78.94

The Theory

Fick's Law:

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