Lipids & Protein Assignment(S)****

Chemical Basis of Life - Part 2 (Lipids & Proteins) Below is a listing which will help you to prepare for the quiz and lab on this material.

CONTENT TO KNOW: (Some review from previous lab)

I. MACROMOLECULES (ORGANIC MOLECULES) - These are the large biological molecules, found in living things

The 4 Main Groups of Organic Molecules are:

 Carbohydrates  Lipids  Proteins  Nucleic Acids

• This lab uses biochemical tests to identify each group of molecules. • The 4 tests and the results, both positive and negative are summarized in the table

below

NAME OF TEST Substance To Be

Identified (+) RESULT RESULT

1. Benedict's Test

MONOSACCHARIDES DISACCHARIDES

yellow, red, or brown Clear Blue

2. Iodine Test (IKI)

STARCH Black color Brown

3. Sudan IV LIPIDS (FATS) Spreads outside the circle

Does not spread outside circle

4. Biuret Test PROTEIN Violet/Purple Color Blue

II. LIPIDS (Fats) - includes fats (glycerides) and oils

Triglycerides - have a Glycerol head and 3 fatty acid tails

Click HERE for a picture of a triglyceride

Saturated Fats - solid at room temperature • (ex: lard, butter)

Unsaturated Fats - liquid at room temperature • (ex: salad oil, olive oil) (shown above)

III.TEST FOR THE PRESENCE OF LIPIDS - The SUDAN III Test - if the substance dissolves into the Sudan III, it indicates lipids are present; the drop moves outside the pencil circle drawn

• NEGATIVE Lipid Test - does not dissolve into solution; stays inside pencil circle • POSITIVE Lipid Test - dissolves into solution and moves outside pencil circle

IV. PROTEINS - Composed of amino acids

• The building blocks (sub-units) of all proteins are AMINO ACIDS • There are 20 different amino acids (AA) • Peptide bonds - the covalent bonds which link amino acids in proteins • The ultimate shape of a protein determines what job it can do • Polypeptides = short proteins

 Examples of Proteins: Hair, Enzymes, Nails, Albumin (egg white)

Click HERE for a picture of an amino acid chain V. BIOCHEMICAL TEST FOR THE PRESENCE OF PROTEINS:

• BIURET TEST for Proteins -

o NEGATIVE BIURET TEST - remains light blue (Left Tube) o POSITIVE BIURET TEST - violet/purple color is seen (Right Tube)

Click HERE for a picture of the Biuret Test

**NUCLEIC ACIDS - DNA & RNA - will be covered in a later lab