You can also find lipids through the means of adding Sudan IV to a solution. The solution turns red if there are lipids present.
Purpose: To show the presence of lipids in various foods.
Independent Variables: The materials tested
Dependent Variables: the translucency of the paper/ the presence of colloidal droplets/ the colour of a substance.
Controlled variables: same paper is used, same amount of materials, same amount of ethanol used, same amount of distilled water, same amount of Sudan IV
Identification of Proteins
Background: Proteins are the most common organic compounds in living cells. They are composed of Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Iron and Phosphorus. Proteins are the building blocks for many organelles, cell membranes, enzymes, muscles and more.
Proteins can be detected by adding copper ions.
Purpose: to show the presence of proteins in various foods
Independent variables: different materials used
Dependent variables: color changes of materials
Controlled variables: volume of materials used, volume of NaOH and CuSO4 used, volume range of HNO3 used.
Materials
Investigation 2 Investigation 3 Investigation 4
*beef fat was not used for experiment due to shortages
*Ethanol replaced isopropanol in the experiment
Procedures
Refer to attached handout in appendix
Observations
Investigation 2: Identification of Carbohydrates – a) Reducing Sugars Test
Investigation 2: Identification of Carbohydrates – b) Starch and Glycogen Test
Investigation 3: Lipid Identification – a) Translucence test
Investigation 3: Lipid Identification – b) Emulsion test
Investigation 3: Lipid Identification – c) Sudan IV test
Investigation 4: Identification of Proteins – a) Biuret test
Investigation 4: Identification of Proteins – b) Xanthoproteic Test
Analysis
Investigation 2: Identification of Carbohydrates – a) Reducing Sugars Test
Investigation 2: Identification of Carbohydrates – b) Starch and Glycogen Test
Investigation 3: Lipid Identification – a) Translucence test
Investigation 3: Lipid Identification – b) Emulsion test
Investigation 3: Lipid Identification – c) Sudan IV test
Investigation 4: Identification of Proteins – a) Biuret test
Investigation 4: Identification of Proteins – b) Xanthoproteic Test
Discussion
The data shown to use by these test shows use which substances have carbohydrates, which substances have lipids, and which substances contain proteins. Using the results from this experiment, we can now arrange our diets in a way that we receive all the substances we need to maintain a healthy diet. For example, using the results from the Xanthoproteic test, we now know that milk is a source of protein. Protein is essential for the development of muscles and organelles. Using this connection, we can conclude that milk can help the development of muscles and organelles, and that we – as humans – should drink more of it for a balanced healthy diet.
This experiment did not run as smoothly as I thought it would. Certain tests had problems that may have resulted in inaccuracy of results or frustration during experimentation.
During the reducing sugars test, there was a problem with the water used to heat the test tubes containing the solutions. The procedure provided did not tell you how much water to heat. Too much water, and the masking tape used to label the test tubes would fall off in the water. Too little water and the tubes would tilt and not stay upright. To improve this experiment, the procedure should state that water should be added to a point where the test tubes are three quarters submerged.
In the Emulsion test, the crushing of the solid ingredients was a very messy task. When crushing a solid in a mortar, you had to add ethanol. The solids were very difficult to mash, and the liquids kept spilling over. If you mashed too hard, it would spill, but it you didn’t grind as hard, the solids would remain solids for ages. To improve this experiment, I would suggest using a smaller sample of solids and liquids. I would reduce the amount from 3 grams to 1.5 grams (of solids) and I would reduce the amount of ethanol used from 10mL to 5mL. In the end of the experiment, only one drop of the liquid I required, so reducing the sample size makes a lot of sense
During the Sudan IV test, we had to “shake the mixture vigorously”. This was a problem because Sudan IV is corrosive and touching it would be potentially dangerous. The instructions don’t specify a safe way to shake the test tubes. I would suggest that the instructions include that you use a test tube stopper to prevent the corrosive solution from spilling.
Conclusion
The only ingredient tested in experiment one that didn’t contain carbohydrates is distilled water. The ingredients that don’t contain lipids are ethanol, Sudan IV and distilled water. The ingredients that don’t contain proteins are distilled water.
by
greg_smith69 (student)
