Testing for Macromolecules

Topics: Glucose, Carbohydrate, Nutrition Pages: 2 (661 words) Published: February 9, 2011
Focused Question:
How can one determine the presence of glucose, starch, lipid, and protein in various samples?

Pre-lab Questions:
Glucose is a monosaccharide. What does this mean?
A monosaccaride is a carbohydrate molecule with three to seven carbon atoms with the corresponding number of hydrogen and oxygen atoms.

Proteins are made of amino acids. What atom is present in an amino acid that is not present in a sugar molecule? One nitrogen atom is present per molecule in an amino acid. Data Collection:

SampleBefore HeatingA. Benedict’s Solution +HeatB. Iodine SolutionC. Biuret Reagent 1. Protein SolutionPurpleLight PurpleDark OrangeLight Purple 2. Glucose SolutionLight BlueOrange-yellow Light OrangeTransparent 3. Sucrose SolutionLight BlueLight BlueLight OrangeTransparent 4. Starch SolutionLight BlueLight BlueDark Brown Transparent 5. Distilled Water Light BlueLight Blue Light OrangeTransparent

1. If there is starch in the substance, the colour changes to a dark brown when drops of iodine solution are added to it. Starch is the only solution that exhibits a major change (dark brown) that is different from the other solutions (orange colour) when iodine is added. It can therefore be inferred that a positive test for starch macromolecules occurs when the solution turns dark brown when Iodine solution is added.

2. If there is glucose in the substance, the substance turns to an orange-yellow colour when Benedict’s Solution is added to it. The colour of the glucose solution when it is mixed with Benedict’s solution with heat is orange-yellow, while all of the sample solutions turn into a light blue or purple colour. We can therefore deduce that a positive test for glucose macromolecules is when the colour changes orange-yellow when Benedict’s solution and heat is added.

3. For the presence of proteins in the substance, it must change its colour to light purple when Biuret Reagent is added to it. The distilled water...
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