Question

EXPERIMENT #1: EGG OSMOSIS

STEP ONE:

Read the introduction in your lab manual on page 233-244.

Watch the video on blackboard entitled “Osmosis Lab Procedure Video 1”

In this lab, decalcified eggs are placed into 4 separate solutions of varying glucose concentrations. The eggs are meant to simulate cells. Mass of the eggs will be recorded initially, and then eggs will be placed into a beaker filled with one of the following:

-Distilled Water

-0.5 M glucose

-1.5 M glucose

-2.0 M glucose

Egg mass will be recorded every 15 minutes, for 90 minutes total.

Changes in egg mass over time will be a result of osmosis--water entering or exiting the egg (“cell”).

Because this lab is being done online, data has been provided for you.

STEP TWO:

Assume that the experiment has been run to completion. Review the following results that were obtained from the experiment:

Osmosis-decalcified eggs

Table 1: Mass of Eggs in grams (pg 237 in lab manual)

Egg in	0 min	15 min	30 min	45 min	60 min	75 min	90 min
Water	85.8	87.8	89.0	89.8	90.9	92.1	93.0
0.5 M glucose	91.1	92.0	92.4	92.8	93.0	93.3	94.0
1.5 M glucose	94.5	93.7	92.9	92.3	91.8	91.0	90.4
2.0 M glucose	93.6	92.2	90.9	89.9	89.1	88.0	87.5

STEP THREE:

Watch the video on Blackboard entitled “Osmosis Lab Procedure Video 2”

Using the data in Table 1 above, you will now calculate the percent change in mass using the following equation (on page 236 of your lab manual):

[new mass-initital mass] [initial mass] x 100

Calculate the percent change in mass for each egg at each time interval and record in table 2 below.

Notes:

-the initial mass used in the equation will always be the mass at 0 min. Thus as you calculate percent change, the only value you should be changing in the equation is the new mass

-the percent change at 0 min will be 0 for all four eggs.

-The first calculation for the egg in the distilled water at 15 minutes has been done for you

Table 2: Percent change in mass (pg 238 of your lab manual

Egg in	0 min	15 min	30 min	45 min	60 min	75 min	90 min
Water	0%	2.33%
0.5 M glucose	0%
1.5 M glucose	0%
2.0 M glucose	0%

STEP FOUR:

Using Microsoft excel, create a graph for table 2 above. Create a “marked scatter plot”. Make sure the graph is properly labeled, with appropriate units.

After creating the graph, save it onto your computer! You will need to turn it in as well as use it to answer the discussion questions at the end.

Answer 1

Okay, let's calculate those percent changes in mass:

Egg in	0 min	15 min	30 min	45 min	60 min	75 min	90 min
Distilled water	0%	2.33%	3.72%	4.66%	5.94%	7.34%	8.39%
0.5M glucose	0%	0.98%	1.42%	1.86%	2.08%	2.41%	3.18%
1.5M glucose	0%	-0.84%	-1.69%	-2.32%	-2.85%	-3.7%	-4.33%
2M glucose	0%	-1.49%	-2.88%	-3.95%	-4.8%	-5.98%	-6.51%

Note that in 1.5 and 2 M glucose the percentages are negative, that means the egg lost mass, this occurs because those concentrations are already hypertonic for the egg (make the egg lose water), while the distilled water and 0.5 M glucose were hipotonic for the egg (make the egg gain water).

Now let's plot this: