Organic Molecules

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Title: Benedict ’s test for Reducing Sugars

Testable Question: Are all carbohydrates reducing sugars?

Hypothesis: If the carbohydrate contains available ketone or aldehyde molecules then they are reducing sugars.

Variables:

a. Independent: Function groups react w/ reagent

b. Dependent: Color change (red, orange, yellow)

Control: Water

Materials:

- 4 mL of each solution (Water, Starch, Glucose, Maltose, Sucrose, Onion Juice, Potato slice, Milk)

- 8 test tubes

- 8 pipetes

- Benedicts regagent

- 150 mL of water

- Beaker

- 1 pair of tongs

- Test tube rack

- Hot plate

- Dropper

- Timer

Procedure:

1. Set up a row of eight test tubes. Use a marker to number them 1 through 8.

2. To each test tube, add 4 mL of the solutions listed above, matching each number to the number on the tube.

3. Add one dropperful (2mL) of Benedict’s reagent to each tube.

4. Mix the reagent and the sample by agitating the solution in each tube from side to side. Record the original color of each tube’s contents in your data table.

5. Heat the test tubes in a boiling water bath for 2 minutes. Record any color changes in the data table you created.

6. Pour the contents of each test tube down the sink and flood with water. Wash out and dry each test tube and ready them for the next exercise.

Title: Lugol’s Test for Starch

Testable Question: Are all carbohydrates polysaccharides?

Hypothesis: If a carbohydrate is a polysaccharide, then it will react with the reagent and change color.

Variables:a) Independent: The type of carbohydrate

b) Dependent: Color change

Control: Water

Materials:

- 4 mL of each solution (Water, Starch, Glucose, Maltose, Sucrose, Onion Juice, Potato slice, Milk)

- 8 test tubes

- 8 pipetes

- Lugol’s regagent

- Test tube rack

- Dropper

Procedure:

1. Prepare your clean test tubes as indicates in the procedure for the Benedict’s Test.

2. To each test tube, add 4 mL of the solutions listed above, matching each number to the number on the tube.

3. Record the original color of each tube’s contents in your data table.

4. Add 5 drops of Lugol’s reagent to each tube; mix and immediately record any color changes that take place. DO NOT heat the test tubes during this test.

5. Pour the contents of each test tube down the sink and flood with water. Wash out and dry each test tube and ready them for the next exercise.

Title: Proteins and Amino Acids.

Testable Question: Do all organic molecules contain peptide bonds?

Hypothesis: If a substance is not a protein, then it will not have peptide bonds.

Variables:a) If it is a protein

b) Color change

Control: Water

Materials:

- 4 mL of each solution (Distilled Water, Egg albumin, Potato starch, Glucose, Amino acid)

- 5 test tubes

- 8 pipetes

- Biuret Reagent

- Test tube rack

- Timer

Procedure:

1. Obtain 5 clean tubes and number them from 1 through 5

2. To the tes tube, add 4mL of the solutions listed above, matching each number to the number on the tube. Record your original color before adding the biuret’s.

3. Add one dropperful (approximately 2mL) of biuret reagent to each tube.

4. Gently mix the reagent and the solution by agitating the solution in each tube from side to side.

5. Allow to sit for two minutes, record your results in your data table and determine whether the solution

Benedicts Test for Reducing Sugars

1. We tested water with Benedict’s reagent because water was the control. The water is the standard of comparison.

2. The sugars glucose, maltose, sucrose, onion juice, potato slice and milk reacted with the reagent because the have an available ketone or aldehyde group.

3. Starch did not react with Benedict’s reagent because...
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