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SOTM LAB: B14 12/99

I. TEACHER NOTES & GUIDELINES

Title of Lab: Effects of Temperature and Solvents on the Cell Membrane

Developers of Lab: Adapted by James Kirby JD726, Jennifer Mortellaro JD449, and James Prockup JD575 from a publication by the Department of Biological Sciences at Western Michigan University, Kalamazoo, MI

Overview of Lab: Description: The purpose of this lab is to illustrate the effects that temperature and solvents have on the cell membrane.

Red beet tissue contains large amounts of betacyanin, a red pigment, located in the large internal membrane vacuoles. When the membrane is damaged, this pigment can cross the vacuole membrane and cell (plasma Membrane). In
Be specific.

DISCUSSION OF PRECONCEPTIONS Have one person, from each group, discuss with the class the group’s answer to each question.

III. EXPLORATION OF SCIENTIFIC PRINCIPLE & INTRODUCTION OF EXPERIMENTAL PROTOCOL

PROBLEM What effect will temperature changes have on a membrane?

EXPERIMENT AND TECHNICAL OOPERATION OF EQUIPMENT

PROCEDURE

1. Cut 5 uniform cylinders of beet using a cork borer with a 4-mm inside diameter. Line up the pieces, cut off the ends and make another cut to obtain 15-mm long pieces (all pieces must be the same size). 2. Rinse each piece for 2-min in a large beaker of tap water to remove the excess red dye that leaked during the cutting procedure. 3. Place one piece into each of the 6 test tubes and write a number on the tube/lid with a marker. a) Frozen (from teacher) b) On ice for 15-mins c) 25C (room temp) for 15-mins d) 37C (hold in your hand) for 15-mins e) 55C for 15-mins f) 80C for 15-mins

4. After temperature treatments, add 5-mL of distilled water, cover with parafilm and allow to stand for 15-mins. During this time the teacher will preview with you the operation of the spectrophotometer. Invert the tubes gently several times during the 15-mins. 5. Pour the liquid from test tube (a) into a clean cuvette. Wipe down the outside of the tube, and