Identifying Carbohydrates

When placing the large test tube in boiling water, be sure to keep the face of the large test tube away from you or any lab partners with safety tongs.

1. Benedict’s solution is added to white grape juice and heated. The color changes from blue to orange. Based on this result, what biological molecules are

The iodine test is used to identify glycogen and starch. These polysaccharides combine with iodine to

A cell, the building block of all living organisms, is composed of four fundamental biomolecules: proteins, carbohydrates, sugars and lipids. Proteins provide a vast amount of functions cells such as they serve as enzymes, provide structural support to cells, and act as antibodies. Reagents are used to spark a chemical reaction. The reagent used to detect protein traces in a substance is Biuret’s. Biuret’s will turn purple if proteins are present and blue if they are none. Biuret’s copper particles, have a charge of +2, are diminished to a charge of +1 when peptide bonds, which are in proteins, are present, creating the color change. Polysaccharides, which are carbohydrates, are most notably known to provide energy to the body, but they also help in breaking down fatty acids. Iodine is the reagent used to determine whether a substance has starch in it. The iodine/starch complex has energy levels that are only for retaining unmistakable light, giving the complex its extraordinarily dark black-blue shade. If there is no starch found, iodine will remain its natural yellowish-brownish color, but if starch is present, iodine will turn blue-black. Monosaccharides, which are sugars, like polysaccharides, provide the body with energy. To detect monosaccharides, the reagent, Benedict’s, is used. Benedict’s reagent is added to a test tube, then it is placed in

C. Pour about one quarter of the first unknown packet into the first cup and add

2. Four unknown samples were included in the lab kit: flax seed meal, potato starch, egg whites, and dried milk. Using the results of the biochemical testing, determine which number corresponds to the correct unknown. (8 points)

b) Benedict test the solution color will change from blue to pink/orange red, indicating simple sugars are present. Lugols test the solution color will change from yellowish brown to dark purple, indicating starch and polysaccharides are present. Sudan iV test the lipid content will turn into red, indicating lipids are

3.Measure and add 0.5g, 1.0g, and 1.5g of sucrose into 3 of the test tubes. Do not add sucrose into the 4th test tube because this will be the control. Lightly shake the test tube to mix the contents together.

Caution – Hydrochloric acid is corrosive to eyes, skin and clothes. Wearing a lab apron, rubber gloves, goggles, and a face shield is essential. Rinse any spills on skin or clothing with plenty of cold water. Clean up spills immediately – ask your instructor for help.

Soda ash to pre-soak your shirts in. Some kits have it included. If not, you can find soda ash, (aka sodium carbonate); at

You only use this if you have an experiment that most likely will explode or splatter during the reaction.

Place tube in the hot water. After about 2-4 minutes in the hot water, check if the solution changed color. If the solution did change color to a more yellow, orange, brick red color, it is positive for the benedict's test. Positive for monosaccharides.

Measure out one scoop of albumin powder (rich protein) and place it into each individual tube.

Solutions and color reaction for Benedict’s test for reducing sugars and 2 iodine test for starch

Half of each tube’s contents are poured into a new test tube each respectively after the tubes are incubated for 1 hour. One set of tubes is tested for: