Identification of Carbohydrates ,Lipids,and Proteins lab
by
greg_smith69 (student)
Introduction
Identification of Carbohydrates – Investigation 2
Background: Carbohydrates are composed of only the elements Carbon, Hydrogen, and Oxygen, and all carbohydrates have the same empirical formula: (C H O). They provide a source of energy to all cells. Plants manufacture their carbohydrates through the process of photosynthesis. Animals need carbohydrates to function, but they cannot produce any on their own, therefore, they have to consume plants, or an animal that eats plants to receive their share.
In this experiment, we use Benedict’s solution to detect certain carbohydrates called “reducing sugars” in the materials. The free aldehyde groups of the reducing sugars are oxidized by the metallic ion found in Benedict’s solution. If a substance does contain “reducing sugars” then the reaction results in the formation if a coloured precipitate.
We also use iodine to detect the presence of starch and glycogen. Iodine solution reacts with the producing a purple black color. It also reacts with glycogen to produce a more brown color.
Purpose: The purpose of this experiment is to determine the types of carbohydrates that are found in various foods.
Independent variables: The materials tested (1% glucose, 1% fructose, etc.)
Dependant variables: The colour change of the materials
Controlled variables: Volume of materials tested, volume of Benedict’s solution added, volume of iodine added
Control Sample: Distilled water
Lipid Identification – Investigation 3
Background: Lipids contain Carbon, Hydrogen, and Oxygen and make up fats, oils, and waxes. Living things need lipids for long term energy storage, insulation, and to form structural components of cells. Lipids are formed when a glycerol combines with three fatty acids.
Lipids can be detected through the means of rubbing substances on paper. If lipids are present, the paper will turn translucence.
Lipids can also be identified through the means of an emulsion test. When a sample is soaked in ethanol, the lipids dissolve. The solution is then poured into water. Since lipids don’t dissolve in water, when the ethanol is diluted, it falls out of solution. We can then search for Colloidal droplets under a microscope. They indicate that a lipid is present.
