Which Functional Groups Were Present in Certain Substances

Which Functional Groups Were Present in Certain Substances

This lab used many test to determine which functional groups were present in certain substance. The Benedicts test was used to identify reducing sugars (glucose and fructose) based on their ability to reuce the Capric ions to cuprous oxide at high pH. The Cuprous oxide is reddish orange in color when shown to be at high levels by the test, and greenish when at low levels. In both the onion juice and glucose solution the reducing sugar levels were very high, because the test came back dark orange. The starch solution had relatively low levels of reducing sugar present and this was seen by the test coming back cloundy blue, green and brown.

Iodine is used to distinguish starch from mono/di/polysaccharides. In the test only two of the six solutions showed any signs of starch being present. The potato juice turned a brownish color with a precipitate indicating a slight presence of starch. The stach solution turned a dark blue/black color indicating a very high presence of starch in the solution. The presence of starch in the potato juice indicates that it does not have as high an amount of carbohydrates as onion juice, but a higher concentration of starch.

The Biuret test is used in identifing the bond between the amino group and carboxyl group in proteins. These bonds are found on adjacent amino acids and are called peptide bonds. In the test, peptide bonds in proteins complex with Cu in Biuret reagent and produce a violet color. Both the egg albumen and protein solution showed hi abundence of proteins. The egg albumen is rich in protein because it is the food source for the individual as it developes into its species.

Sudan IV is a test that functions by a lipid's ability to selectively absorb pigments in fat-soluble dyes. In both instances the salad oil separated from the other solution (water and Sudan IV). The oil moved to the top of the test tube, while the water and Sudan IV moved under, not mixing. However, the oil, high in lipid content had absorbed much of the die when added to the Sudan IV test tube. The potato juice seemed to form a precipitate when mixed with Sudan IV, it was very cloudy and could not be seen through.