Osmosis

Topics: Osmosis, Diffusion, Cell wall Pages: 4 (1254 words) Published: December 7, 2012
Lab 1
7.2 Osmosis
Introduction
Osmosis is the diffusion of water across a selectively permeable membrane in response to a differing overall solute concentration (Starr, Evers, and Starr 85). Most polar molecules such as sugars and proteins cannot freely pass through a lipid membrane; although water molecules are polar they are small enough to pass though the membrane freely. This special case of diffusion that involves the movement of water molecules across a membrane is called Osmosis. This process is very important to maintain the water content in plants cells; it is the vital step in the transport of fluids in living organisms. Without the process of osmosis plants would dehydrate and die. It is a matter of life and death. Cells exposed to hypotonic solutions will take up water, swell, and burst. Cells exposed to hypertonic solutions will lose water, and shrink.

Material and Methods
* Four 15cm lengths of dialysis tubing, soaking in dH20
* Eight 10cm pieces of string
* Ring stand and funnel apparatus
* 25mL graduated cylinder
* China marker
* Four 400mL beakers
* Dishpan half filled with dH20
* Paper towels
* Balance
* Source of dH20 (at each sink)
* 15% and 30% sucrose solutions
1. Obtained one of four of the precut and presoaked dialysis tubing from bowl of dH20. 2. Folding over one end of the tubing it was tied tightly with string. 3. The opened end of the tubing was slid over the stem of the funnel, using a graduated cylinder filled bags 1-4 as follows: Bag 1. 10mL dH20 Bag 2. 10mL 15% sucrose Bag 3. 10mL 30% sucrose Bag 4. 10mL dH20. 4. As each bag was filled, any excess air was forced out by squeezing the bottom of the tube. 5. Each open end of each bag was then folded over and tied tightly with string. 6. Each bag was then rinsed in the dishpan containing dH20, and then gently blotted off any excess water with a paper towel. 7. Then, one at a time each bag was weighed to the...
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