<<

Identification of Biomolecules Bio 2402 Lab Our physical bodies are essentially a collection of common and exotic chemicals. Many of these chemicals are simple inorganic combinations such as sodium chloride, hydrochloric acid, molecular , and dioxide. Most chemicals comprising our bodies are larger more complex organic . The biochemical reactions that are occurring constantly within our cells synthesize new, larger molecules or decompose larger molecules into smaller pieces. Anabolism is a term used for all the synthesis reactions occurring at any time; Catabolism is a term that refers to all the decomposition reactions occurring at any time. is a term that refers to ALL the reactions that might be occurring in the body. While our bodies can metabolize a wide variety of organic molecules, the vast majority belong to three major groups: , and . We can perform simple tests to identify some of these molecules by adding indicators to a solution to be tested. A change in color, or other physical characteristic usually indicates the presence of a particular chemical. A. Simple carbohydrates (; simple sugars). Benedicts solution causes these sugars to turn green, yellow, orange or red when heated to boiling. The color of a positive reaction depends on how much sugar is present (green indicates low levels; red high sugar levels) B. Complex carbohydrates ( or ). Lugol’s iodine causes a solution containing to turn dark blue to black. The more starch there is the darker the color. C. Lipids ( and oils). Large amounts of concentrated lipids leave a translucent stain on paper after drying. D. Proteins (and Polypeptides) Biuret solution causes a solution to turn pink or violet. E. Sodium Chloride (NaCl) is a common inorganic constituent of body fluids. Silver nitrate causes solutions containing sodium chloride to develop a white precipitate. The first step in learning to detect these chemicals is to perform control tests with substances known to contain or not contain specific chemicals. You will perform each of the above tests on a “positive” and a “negative” solution (the “negative” is usually water). After completing the tests you will see both the positive and negative results for each kind of above.

Control Test Procedures: 1. Sugars: a. take two clean test tubes and label one su+ and the other su-. b. add about 1 cm of solution (10% Karo) to su+ c. add about 1 cm of DI water to su- d. add 10 drops of Benedict’s solution to each test tube e. place both test tubes in a boiling water bath at your table for about 2 minutes f. record the reaction as either “+” or “-“ in the table below 2. Starches a. add a drop of boiled starch solution (1% starch) to one of the wells in the spot plate and a drop of water to another well b. add 1-3 drops of Lugol’s iodine to each of the wells c. record the reaction as either “+” or “-“ in the table below 3. Lipids a. with a dropper add a drop of oil (vegetable oil) to one half of a paper towel b. with another clean dropper add a drop of DI water to the other half of a paper towel c. place the paper towel in the incubator on a warming tray for 5 minutes d. record the reaction as either “+” or “-“ in the table below 4. Proteins a. take two clean test tubes and label one pr+ and the other pr- b. add about 1 cm of protein solution to pr+ c. add about 1 cm of DI water to pr- d. add 10 drops of Biuret solution to each test tube e. record the reaction as either “+” or “-“ in the table below 5. Sodium Chloride (NaCl) a. take two test tubes and label one NaCl+ and the other NaCl- b. add about 1 cm of sodium chloride solution to NaCl+ c. add about 1 cm of DI water to NaCl- d. add a few drops of silver nitrate solution to each tube e. record the reactions as either “+” or “-“ in the table below Experimental Tests In the second part of this exercise you will be testing each of the solutions that you are given by adding indicators to test for the above molecules. Before testing each solution indicate your hypotheses concerning which of the substances each contains. Rather than writing out each hypothesis for each unknown solution indicate what you expect to find by checking the appropriate boxes for each solution. Note: to save space and time, you don’t need to write out your complete set of hypotheses for each solution – just indicated which molecules you expect to be present with a “+” or “-“ sign in that column under expected results; these are your “hypotheses”) Then perform the tests on each of the solutions and record your results in the table on your data sheet. Use the spot plate for the starch tests; use a paper towel for the oil test; use test tubes for the benedicts and protein tests. You will need to clean and rinse the test tubes in DI water and reuse them during this lab Cleanup and Disposal Discard all solutions into the sink with the water running Dispose of empty test tubes in the glass disposal box Dispose of plastics and paper towels in trash Clean spot plates with soap and water and return it to your lab table Make sure the hot plate is turned off and unplugged before you leave; leave the beaker and boiling stones on the hot plate Name:______Group:______Due Date:______Identification of Biomolecules Bio 2402 Lab Data Sheet

Control Tests: Write out your hypothesis being tested for each control test below and then record your results as a “+” or “-“ in the column to the right. Hypothesis being tested Result +/- sugar test

Sugar Sol

DI water starch test

Starch Sol

DI water test

Oil

DI water protein test

Protein Sol

DI water NaCl test

NaCl Sol

DI water

Were all of your hypotheses verified by your experiments, if not explain?

Why are these called “control” tests What would be the consequences for the rest of this experiment if any were not verified?

Expected Results (Hypotheses) [+/-] Experimental Results [+/-] solution sugar starch lipid protein salt sugar starch lipid protein salt apple juice diet soda powdered sugar sol potato sol bottled water tuna sol

List at least five assumptions that you are making when you formed your hypotheses for the unknowns.

Make a table that lists any discrepancies between what you expected to find (your hypotheses) and what you actually found (your experimental results) in each of the solutions. Then explain each of these specific discrepancies (use additional sheets as needed):