IB+Lab+-+Invertase

3 Chemistry of Life - 3.1 Chemical elements and water - 3.2 Carbohydrates, proteins and lipids - 3.3 DNA structure - 3.4 DNA replication - 3.5 Transcription and translation - 3.6 Enzymes - 3.7 Cell respiration - 3.8 Photosynthesis - Biochemistry Labs - DNA Labs


 * Invertase**

//Introduction// Our most common food sugar—the disaccharide, sucrose—is formed in all green plants. The metabolism of sucrose in the animal body begins with the action of invertase (sucrase) which hydrolyzes the disaccharide to two monosaccharides, fructose and glucose. This same enzyme is also produced by plants and fungi.

//Materials// Sucrose (0.25 M solution) Glucose (0.25 M solution) Benedicts solution (in dropper bottle) Distilled water (100 ml) Hot plate with water bath Stirring rods (2) Beaker (50 ml) Test tubes (5) Test tube rack Pipet or syringe to measure 3 ml Tes-Tape (tape from drug store used to test for glucose in urine samples) Balance or teaspoon

//Procedure// 1. Prepare yeast by mixing 1 teaspoon (3 g) dry yeast with 20 ml of distilled water. Let stand for 20 minutes. 2. Fill each of two test tubes 1/3 full with sucrose solution. 3. Add 3 ml yeast suspension to one tube. Mix. 4. Add 3 ml distilled water to the other tube. Mix. 5. After 10 minutes test each test tube plus the yeast suspension with a strip of Tes-Tape. (Benedict's test for reducing sugars can also be used here since sucrose will give a negative Benedict's test and glucose/fructose will give a positive test (yellow-orange-red) depending on the amount of reducing sugar present. Remove about 2 ml of the solution, place in another test tube, add 10 drops of Benedict's solution and place in a boiling water bath for about 3 minutes. Prepare a glucose solution for comparison.)

//Results// For best results, do not go over the recommended incubation period. Both the Tes-Tape and Benedict's should give positive tests for samples from tube 1 while the tube without yeast gives negative results.