C2cEggDiff

EGG OSMOSIS

PRE-LAB

Everyone knows what a chicken egg looks like. You probably picture a white or brown hard oval, slightly pointed on one end, two to three inches long. What makes it hard? Why is it hard? Is it porous? Is it alive? Is it a cell? Compare a normal chicken egg to an ostrich egg. How are they similar? How are they different? Why are bird eggs larger than most cells. Pay special attention to the pores in the ostrich egg. How is the outside of an egg different from a plant or animal cell? Where is the cell membrane of a chicken or ostrich egg?

BACKGROUND

Cells have an outer covering called the cell membrane, which controls what moves into and out of cells. The cell membrane must permit some substances to pass through, yet prohibit other substances from doing so. It may also allow rapid diffusion of some substances and very slow diffusion of others. Diffusion is the movement of particles from where they are more concentrated to where they are less concentrated. Osmosis specifically refers to the diffusion of water through a membrane. Membranes can be referred to as differentially permeable, selectively permeable, or semi-permeable.

In this lab, you will perform an experiment that will illustrate osmosis through a semi-permeable membrane. A chicken egg will be used as the model cell, because the egg is actually a single large cell. The egg white, or albumin, which surrounds the yolk, contains water and several different proteins.

SAFETY

Follow standard lab safety procedures. Be careful with glassware.

MATERIAL

One ostrich egg per class

Each group of 2-3 students will need;

1 raw egg 80-100 ml of distilled water

80-100 ml of white vinegar balance

1 100 ml graduated cylinder 1 250 ml glass jar with lid

Paper towels 80-100 ml of dilute syrup (corn)

Weigh boats 1 plastic spoon

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10/7/11ASIM Biology: Cells

C2cEggDiff

PROCEDURE

Day 1.

  1. Place the egg in a weigh boat. Find the mass of the dry egg. Record your findings in the table under “Mass of egg, Day 1.” Place the egg in jar.
  1. Using the graduated cylinder measure enough vinegar (80 to 100 ml) to cover the egg in the jar. Record the amount of vinegar measured under Day 1.

Day 2.

  1. After 24 hours, carefully remove the egg from the jar, rinse it with water, and dry it with a paper towel. Pour off the vinegar into a graduated cylinder and record its volume under Day 2.
  1. Place the egg in a weigh boat. Find the mass of the egg. Record your findings in the table under “Mass of egg, Day 2.”
  1. Rinse the jar and dry it thoroughly. Return the egg to the jar.
  1. Measure enough syrup (80 to 100 ml) to cover the egg in the jar. Record the amount of syrup measured under Day 2.

Day 3.

  1. After 24 hours, carefully remove the egg, rinse and dry it. Place egg onto the weigh boat. Record the mass of the egg under Day 3. Measure and record the volume of the remaining syrup.
  1. Rinse the jar and dry it thoroughly. Return the egg to the jar.
  1. Measure enough water (80 to 100 ml) to cover the egg in the jar. Record the amount of water measured under Day 3.

Day 4.

  1. After 24 hours, carefully remove the egg and dry it. Place the egg onto the weigh boat. Record the mass of the egg under Day 4. Measure and record the volume of the remaining distilled water.
  1. Rinse the jar and dry it thoroughly.
  1. Complete the Analysis section of the student data sheet.

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10/7/11ASIM Biology: Cells

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STUDENT DATA SHEETNAME ______

EGG OSMOSISDATE ______

Egg # / Day 1 / Day 2 / Day 3 / Day 4
Mass of Egg / ml of Vinegar / Mass of Egg / Change in mass / ml of Vinegar / change in vinegar / ml of syrup / Mass of Egg / Change in mass / ml of syrup / change in syrup / ml of water / Mass of Egg / Change in mass / ml of water / change in water / Change in mass from day 1 to day 4 of egg
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Class Avg
1. How does the mass of the egg change each day?
2. What causes the change in the mass of the egg?
3. From Day 1 to Day 2 does the volume of the vinegar change? Is the change an increase or decrease? Explain how the change occurred.
4. From Day 2 to Day 3 does the volume of the syrup change? Is the change an increase or decrease? Explain how the change occurred.
5. From Day 3 to Day 4 does the volume of the water change? Is the change an increase or decrease? Explain how the change occurred.

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10/7/11ASIM Biology: Cells