Macromolecules Web site for further clarification: http://www.srvhs.org/staff/teachers/rgroch/bio/bio_home_page/idorgcomp.pdf I. Introduction A. Define categories of macromolecules 1. Carbohydrates a. monomer- sugar b. linkage- glycosidic 2. Protein a. Monomer- amino acid b. Linkage- peptide bond 3. Lipid a. Monomer- Fatty acid, glycerol b. Linkage- ester 4. Nucleic acids a. Monomer- nucleotide b. Linkage- Phosphodiester B. Refer to bullet handout for details of introduction II Procedures A. Tests for Carbohydrates 1. Iodine test for the presence of starch. http://www.elmhurst.edu/~chm/vchembook/548starchiodine.html a. Iodine intercalates into the helical structure of starch polymers resulting in the color change from yellow to blue/black b. add 3- 5 drops of IKI reagent to approximately 1 ml of sample to be tested. i. If sample is a solid, a slurry of the solid can be made with water to facilitate testing. c. a positive result is a blue/black color d. a negative result is a yellow/brown color. (anything other than blue/black/grey is considered negative) 2. Benedicts test for reducing sugar http://www.biosci.ohiou.edu/introbioslab/Bios170/170_2/benedict.htm a. The Cu+2 ion contained within the reagent is reduced to Cu+ by reacting with the free aldehyde or ketone group present in all monosaccharides and some disaccharides. b. Mix approlomately equal volumes of solution to be tested with the Benedicts reagent. Heat in boiling water bath for 5 minutes. c. positive test is noted for color changes to green, orange, brick red or brown. d. Negative results are seen as blue (No color change) B. Tests for lipids 1. Brown paper test a. Lipids do not evaporate readily into air. They do, however, impregnate uncoated brown paper to form a translucent spot. Unlike aqueous solutions, the lipid residue will not disappear (evaporate) after 30 minutes. b. Spot one drop of substance to be tested onto a piece of brown paper. Observe after 30 minutes for translucency. 2. Emulsion test a. Lipids do not dissolve in water, but do dissolve in ethanol. This characteristic is used in the emulsion test. b. Do not start by dissolving the sample in water, but instead shake some of the test sample with about 4 ml of ethanol. Decant the ethanol/ lipid solution into a test tube containing 4-8 ml of water. (leave any undissolved substances behind.) If there are lipids dissolved in the ethanol, they will precipitate in the water, forming a cloudy white emulsion. C. Tests for Protein 1. Biuret test. http://www.biosci.ohiou.edu/introbioslab/Bios170/170_2/biuret.htm a. Biuret reagent contains Cu+2 ions that form of a tetracoordinated cupric ion (Cu+2 ) with amino groups participating in a peptide bond. This complex is violet in color. Note- a minimum of 3 amino acids must be covalently bonded via peptide bonds to react positively with biuret reagent. b. Add equal volumes of substance to be tested and biuret reagent to a test tube. Mix and observe for color change. c. positive results appear violet or rose colored. (Rose color indicates presence of short chain polypeptides.) d. Negative results appear to remain blue in color. e. Production of a yellow color indicates the presence of a strong acid that interferes with the accuracy of this test. D. Design an experiment to test for the presence of each of the above 3 categories of macromolecules in various food substances of choice. E. Based on what you know about living organisms, would you expect many food substances to contain nucleic acids?