Exercise 1: Starch and Sugar

Data Table 1. Benedict’s Reagent Data.

Sample

Initial Color

Final Color

Reducing Sugar Present in Sample? Y or N

dH2O

Clear

Blue

N

Albumin

Yellow

Blue

N

Unknown

Clear

Blue

N

Milk

White

Yellow

Y

Glucose

Clear

Orange

Y

Data Table 2. Lugol’s Iodine Data.

Sample

Initial Color

Final Color

Starch Present in Sample? Y or N

dH2O

Clear

Amber

N

Albumin

Clear

Amber

N

Unknown

Clear

Amber

N

Milk

White

Beige

N

Starch

Cloudy

Dark Blue

Y

Raw Potato

Beige

Black

Y

Questions

A) In each of the two tests (starch and sugar) a positive and negative control was used. What was the positive control in each of the tests and what was the negative control. Explain your answers.

B) Did the Benedict’s test for reducing sugars net a positive or negative result for milk? Research the sugar content of milk and the definition of a reducing sugar to explain if your result is what you would expect.

C) Based on your results, is sugar and/or starch present in your Unknown? Use your results to explain your answer.

Exercise 2: Proteins and Lipids

Data Table 3. Biuret’s Reagent Data.

Sample

Initial Color

Intermediate Color

Final Color

Protein Present in Sample? Y or N

dH2O

Clear

Blue (Light)

Blue (Light)

N

Albumin

Yellow

Purple

Purple

Y

Unknown

Clear

Purple

Purple

Y

Milk

White

Purple

Purple (light)

Y

Data Table 4. Lipid Observations.

Sample

Sample Observations

Lipid Present in Sample? Y or N

Distilled water

The distilled water did not take the Sudan III red coloring outside of the pencil line.

N

Albumin

Albumin did not take the Sudan III red coloring outside of the pencil line.

N

Unknown

The unknown did not take the Sudan III red coloring outside of the pencil line.

N

Milk

The milk did take a very small amount of the Sudan III red coloring outside of the pencil line.

Y

Vegetable oil

The vegetable oil easily made it outside the pencil line with the Sudan III red coloring.

Y

Questions

A) Review the Data Tables in Exercises 1 and 2. Compare the results of the Unknown for all tests to the results for the various known samples to determine the identity of the Unknown. Explain the identity of the Unknown using your experiment results in the exercises to help explain and support your answer.

B) Eggs are known to contain cholesterol which is a lipid. Did your experiment results indicate a presence of lipids in the albumin solution? Think about this result and where cholesterol is present in eggs to explain how your results support or reject cholesterol in eggs. How could you test this? Explain the experiment that you would perform to test this.