Chemical Composition of Cells:

Experiment Instructions (Lab Report)

By the end of this unit. you should be able to do the following:

Describe the dif1’erence benxeeii organic and inorp•anic chemicals.

2. Relate oxygen content of a chemical io whether it is hydrophilic or hydrophobic.

3. Explain the relationship benveen starch. liber. and complex carbohydrates and lio they relate to glucose. sugar. and siiiiple sugars.

4. Describe how to use iodine. Benedict, and Biurei tests to identify starch. sliliple suears. and protein respectively.

5. Describe the color of a positive reaction and a negative reaction for iodine. Benedict. and Bniret tests.

6. Describe how an eniulsitier chan_•es the iiiixing of oil and waier.

7. Identify the Independent, Dependent, and Control Variables iii your experiment.

JL4TERL4LS NEEDED

1 boH1e of’ iodine (Get ”Iodine Tnicture” or Betadiiie antisepiic in the pharmacy seciion. DO NOT use decol( rized iodine.)

1 boH1e of blue or ereeii food coloring I small potato

1 small onion

1 leaf of lettuce I stick of“ butter 1 egg yolk

vegetable oil (or other type of cooking oil)

tap water sugar

com starch

4 “starcliy” foods from your kitchen (foods you tlihik contain stncli)

-     Choose 1 liquid and 3 solids

3 “fatty” foods from your kitchen (foods yort think contain 25% fat or more)

• Deteriiiine fat content by taking the grams of fat on the nutrition label by the total gram weight of the serving. If the food is a liquid, divide by the total inL volume as each mL is approxhnately 1 grain.
• Common fatty foods include artificial cheese (AmelJcw or “sliced” cheese), cheddar cheese, salad, bologna/potted meat (mash up first), potato chips, pork rinds, chocolate candy, mayonnaise, peanut butter, and uncooked sausage or bacon (chop up first).

3 — 6 drinking glasses Coffee pot or microwave

Don’t Foreet to lill ffff fhe Experimeiit Frnrkf/fQ Sheef for eaclt .s#ffiori off/ie

exercise. Remewher to take ito wore than 4 pictfires for the lab report.

COMPLEX CARBOHYDRATES

Iodine turns blue-black in the presence of starch, but not fiber. You will be mixing iodine with water, com starch, lettuce, table sugar, vegetable oi1, potato, onion. and three “stnrcliy” foods from the kitchen to test for starch.

loiline Test

1. In a clear container. add several drops of iodine to 1/4 cup of water in a drinking glass. Mix and observe. Notice the orange or amber color of iodine. This means there is no starch present. This is a neeative control experiment; keep it for reference.
2. In a clear container, add 1/2 teaspoon of starch to 1/4 cup of water in a drinking glass. Mix and observe the cloudy white color of starch. Add several drops of iodine. Mix and observe. Notice the iodine/starch solution has turned black or dark purple. This means there is starch present. This is a positive control experiment; keep it for reference.

3. Tear a small lettuce leaf and drop iodine on the tom edge. Notice that the leaf may turn a light orwge. just like the water, but doesn’t ttun black. This is another negative control experilTlent showing that iodine doesn’t tins fiber black.
4. (Hypothesis) Repeat the test with sugar water, vegetable oil, and any of the “starcliv” foods you chose that are liquids.
5. Cut a small cube of potato, onion and a chunk froiii each of the t1ii’ee “starcliy” foods you chose that are solids.
6. (Hypothesis) Add several drops of iodine to each and observe the color for amber or black color.

Conclusions - Which foods contained starch? Which did not? How did your hypothesis match your results?

L&IDS

Hydrophobic chemicals (like fat and other lipids) do not mix with water. Hot water mixed with a food will melt the fats and cause them to float to the top in little bubbles or even a complete layer. However, if an eniulsifier is present, the fats will stay iiiixed with the water. You will be iiiixing hot water with butter, egg yolk. and thi’ee “fatty” foods from the kitchen to test for emulsifiers.

Test for Emulsifiers

Safety Note — This is the most dangerous experiment you will do all semester because you will be workine with hot water and drinking glasses. DO NOT touch drinking glasses with your bare skin once hot water has been added. Wait at least 15 minutes for the water to cool down before touching with bare skin.

1. Heat water to steaming in a coffee pot, the nicrowave, or from a very hot tap. DO NOT boil water. (If using the microwave, use a microwave safe container and heat in 30 second increments to avoid boiling.)
2. Add 1 cup of hot water to a drinking class. Add a tablespoon of butter (1/8“ or a stick) to the hot water and stir for 30 seconds. Let the cup sit for 5 minutes.
3. Note the bubbles or layer of oil floating on top of the water. Add 1 drop of blue or green food coloring and mix again. Note that the top layer does not absorb the dye. The floating oil that excludes the dye means there is no emulsifier present. This is a negat’w’e control: keep it for reference.
4. Separate an egg yolk from the white and break up the yolk in the bottom of a drinking glass. (See YouTube for videos on how to separate an egg yolk.) Add 1 cup of hot water and stir for 30 seconds. Let the cup sit for 5 minutes.
5. Note that the egg yolk (which is 33% fat) stays mixed with the water. Add 1 drop of blue or green food coloring and mix again. Note that the dye mixes tlu‘oughout