Essay On Starch Macromolecules

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:

Sample Before Heating A. Benedict’s Solution +Heat B. Iodine Solution C. Biuret Reagent
1. Protein Solution Purple Light Purple Dark Orange Light Purple
2. Glucose Solution Light Blue Orange-yellow Light Orange Transparent
3. Sucrose Solution Light Blue Light Blue Light Orange Transparent
4. Starch Solution Light Blue Light Blue Dark Brown Transparent
5. Distilled Water Light Blue Light Blue Light Orange Transparent

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 and starch, sucrose and glucose solutions all turned transparent when the Biuret Reagent was added, but the protein solution turned light purple. Therefore, a positive test for the presence of protein macromolecules is when the solution turns light purple when Biuret Reagent is
added.

5. The purpose of having distilled water is to use it as a control to test the procedure for false positives. If the distilled water results in a positive test, one can immediately infer that there was an error during the process (contaminated water, dirty test tubes, etc.) since there should not be any macromolecules in pure water.

6. Retrieve a small amount of breakfast cereal into four test tubes separately. Add 1 drop of Benedict’s solution to one test tube and heat it in a hot water bath, 1 drop of iodine solution to the second test tube, and 1 drop of Biuret reagent to the third, and distilled water for fourth test tube (used as a control). If the first test tube turns orange-yellow, then glucose is present. If the second test tube turns dark brown, starch solution is present. Finally, if the third test tube turns light purple, it can be deduced that protein is present in the cereal.

7. High amounts of glucose and lipids in one’s body can indicate a risk of heart related conditions such as coronary artery disease and the development of diabetes. A test that can be used to predict eh presence of glucose in urine is adding Benedict’s reagent. Glucose found to be present in urine is an indication of diabetes mellitus (only glucose is indicative of diabetes). When a reducing sugar is detected in the urine, further tests have to be undergone to verify which sugar is present. High levels of protein can indicate a woman’s pregnancy as well. High levels of protein can also help indicate if one is experiencing kidney failure, usage of anabolic steroids and other hormones.