1. Investigation: Oil and Water (cell membrane)
TEK
7.7 E compare the function of a cell to the function of organisms such as removal

2. Background
All of the chemical reactions inside the cell take place in water. Additionally water surrounds the cells. 46% of your body’s mass is comprised of eater water located inside your cells, with another 23% comprised of water located outside the cells. Add it up.. and your body consists of approximately 70% water!

3. More Background Information
Most lipids do not dissolve in water. A cell’s membrane is composed of type of lipid that has two parts: a water- loving (hydrophyllic) head and a water-hating (hydrophobic ) tail. The cell membrane is called the phospholipid bilayer.
Why is it important that cell membranes be composed of lipids ?

4. Procedures
In one open contain you will find water with food coloring in it, and in the other milk. In a closed water bottle, oil has already been added to water with food coloring in it.
Pour the milk into the colored water and stir it using the provided rod.
Shake the water bottle to mix the oil into the water.
Record your observations below.
Clean up: rinse out the containers and place the supply tray back on the counter.

5. Review the Lab

6. Review: Analysis Questions
Why does a mixture of oil and water behave differently from a mixture of milk and water?
Water is charged negatively on the oxygen end, and positively on the hydrogen end. Oil does not have a charge (it's neutral), so the oil does not mix with the water. The milk and water both have charges , so the mix.
2. From what you have observed in this activity, why is it important for a cell membrane to be composed of lipids.
It is important , so the cell regulate (control) how much water is in a cell.

7. Review Analysis Questions
3. The outside of a cell is surround by water. Explain how the water- hating nature of lipids can keep a cell’s insides separate from its outside. The water-hating nature of the lipids makes a wall to hold in the water on the inside of the cell. 4. Predict what you think would happen if the cell membrane was made out of a water- soluble molecules instead of the water-hating lipid. Answers will vary