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Unformatted text preview: 3-1 SPRING 2010 NAME______________________ BTNY 210 SECTION (DAY/HOUR)____________________ LABORATORY #3(MOVEMENT OF WATER INTO AND OUT OF CELLS; RESPIRATION) Lab #3 Objectives:1) study how different factors affect diffusion 2) know the difference between diffusion and osmosis 3) be able to predict direction of water movement across a selectively permeable membrane 4) recognize plasmolysis and the conditions required to cause it 5) learn about the inputs and outputs of respiration NOTE: We ask that you work in groups of three for the osmosis experiment on page 3-4 and the respiration experiment on page 3-7. These experiments need to be setup at the beginning of class so you have adequate time to observe the results. The rest of this weeks lab is to be done individually, but feel free to work through and discuss them with your lab group; however, your answers should be your own. Your two group members are: andA. DIFFUSION 1. In your own words define diffusion: When we think about diffusion, we have to understand the following: All molecules have energy. In fact, individual molecules actually "bounce" around because of this inherent energy. Molecules that make up solids are not bouncing very much whereas molecules that make up gases are bouncing quite a bit (relatively speaking). The only time when molecules are not bouncing or moving is at 0 Kelvin, or absolute zero. Because molecules move, they can diffuse. The movement of molecules during diffusion is purely random. Eventually (if you wait long enough), molecules that originate from a point source will diffuse and become distributed evenly throughout the system. 3-2 One factor that affects the rate of diffusion (how fast molecules diffuse) is the molecular weight of the molecule. You will examine two test tubes containing solidified gelatin. Two days ago, 5 drops of neutral red (molecular weight = 289 g/mole) were placed on top of the gelatin of one tube. At the same time, 5 drops of aniline blue (molecular weight = 738 g/mole) were placed on top of the gelatin in the other tube. 2. Before you look at the tubes, which substance do you think would have a faster rate of diffusion, the neutral red or the aniline blue and why? 3. Now look at the tubes. Which compound showed the faster rate of diffusion? 4. Will the molecules stop moving when diffusion stops (when the molecule concentration is uniform in the tube)? 5. Are the water molecules in the gelatin also moving and diffusing? Temperature is another factor that affects the rate of diffusion. Examine the two agar plates. Two days ago, a single drop of malachite green was placed in the center of each plate. One plate was left at room temperature (78F/25C) while the other plate was placed in the refrigerator (41F/5C)....
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This note was uploaded on 02/23/2012 for the course BTNY 210 taught by Professor Staff during the Spring '08 term at Purdue University-West Lafayette.
- Spring '08