Membranes
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LAB 2: BIOLOGICAL MEMBRANES

Introduction  

Many believe that life as we know it would not be possible without biological membranes. This lab is designed to explore the dynamic structure of biological membranes.  

Pre-Lab Questions  

            1.         What are the steps in the scientific method

           

            2.         Give an accurate definition of diffusion:  

 

            3.         Give an accurate definition of osmosis:  

 

            4.         Define Hypotonic, Hypertonic and Isotonic

 

            5.         What is a contractile vacuole in Paramecium?  

 

            6.         Define Plasmolysis?

 

Procedure:  

You will again be working in teams of two students. You will be given a number of materials and will use the scientific method to answer a question or demonstrate a process and if possible organize and quantify your results.  

Question 1 What is the rate of diffusion of dye molecules in water (remember to quantify) ? You will be given the following materials:                                             

                                                Ruler

Sheet white Paper

Petri Dish

Dye Solution

Water  

 

Question 2 What happens when a model cell is placed in a hypotonic solution (remember to quantify)?

You will be given the following materials:  

                                                Dialysis Tubing (behaves like a biological membrane)

                                                Dental Floss or tubing clamps

                                                Raw eggs that have soaked in vinegar for 1 week prior to lab*

                                                30% sucrose solution

                                                Large Beaker

                                                Distilled Water

                                                Balance           

 

Question 3 -  Does Paramecium have the ability to osmoregulate (control how much water it contains), remember to quantify! You will be given the following materials

 

                                                Live Paramecium

                                                Compound Microscopes

                                                Slides and Coverslips

                                                Solutions of Distilled Water and 1% and 5% Salt Solutions

                                                Stopwatch

 

Question 4 Demonstrate the process of plasmolysis (this one is more difficult to quantify). You will be given the following materials:

 

                                                Live Elodea leaves

                                                Compound Microscope

Slides and Coverslips

Solutions of Distilled Water and 1% and 5% Salt Solutions 

 

Materials: See questions above

 

References:  

Helms, D.R., C.W. Helms, R.J. Kosinski, and J.R. Cummings. 1998. Biology in the Laboratory, 3e. New York: W.H. Freeman. 

Johnson, Leland. Using Paramecium to demonstrate osmotic homeostasis. 

Kaplan, Eugene H. 1976. Experiments in Life Science - A Laboratory Guide, 2nd ed. New York: MacMillan 

Tharp, Gerald D. 1993. Experiments in Physiology, 6th ed. New York: MacMillan.