Lab Report Osmosis

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The effect of osmosis on artificial cells with different concentrations of sucrose

Alex McRae
Biology 120-902
Grand Valley State University
1 Campus Drive
Allendale, MI 49401
mcraeal@mail.gvsu.edu

Abstract
In this study, we tested the validity of osmosis in artificial animal cells. Osmosis is the diffusion of free water across a membrane. The purpose of the study was to calculate the rate of osmosis in artificial cells containing different concentrations of sucrose and water. We studied the rate of osmosis in artificial cells by creating five different dialysis bags with different concentrations of both sucrose and water and calculating the cumulative change in weight ever 10 minutes for 90 minutes. Our results for the artificial cells showed different concentrations moved from high to low concentrations- through hypotonic movement or hypertonic movement. Introduction

The main purpose of this paper is to assess the rate of change with osmosis for different concentrations of sucrose in artificial cells. Since the human body is composed of trillions of cells that contain roughly 85% of water, makes osmosis a very important concept (Carmichael, Grabe and Wenger). The forces that affect osmosis are the concentrations of solutes surrounding the cell or inside of the cell. Water will then move across the cell membrane and create a balance of water between the cell and its environment (Reece et al. 133). In order to calculate the average rate of change for our artificial cells, we must understand tonicity as the ability of a nearby solution to cause a cell to lose or gain water, depending on its concentration of non-penetrating solutes relative to solutes inside the cell (Reece et al. 133). The dialysis bags used in this experiment have membranes which are selectively permeable, which only allows particles specifically small enough to pass through (Carmichael, Grabe and Wenger). In a hypotonic solution, water goes into the cell because the solute is more concentrated inside the cell, while in a hypertonic solution, water moves out of the sell because the solute is more concentrated outside of the cell. We are testing the effect of osmosis on different concentrations of artificial cells by calculating the cumulative change in weight and the corrected cumulative changes in weight and by determining whether a solution is hypertonic, hypotonic or isotonic. We predicted that a dialysis bag holding tap water in a beaker also containing tap water is in an isotonic solution. While 20% sucrose, 40% sucrose and 60% sucrose in beakers containing tap water is considered hypotonic solutions. Lastly the dialysis bag holding tap water in a beaker containing 40% sucrose is a hypertonic solution. This will result in isotonic solutions remaining at the same weight, hypotonic solutions gaining weight and hypertonic solutions losing weight. We tested this by creating the five different dialysis bags with different concentrations of sucrose in order to measure the weight change in grams of the bag after nine 10 minute increments. Methods and Materials

This experiment took place on Monday, February 6th, 2011. During this time, we tested the effects of different sucrose concentrations on the rate of osmosis in artificial cells we made with dialysis tubing. We studied five different dialysis bags containing 10mL of different concentrations of tap water and sucrose. Two contained tap water while three contained different concentrations of sucrose, varying from 20% to 60%. Each bag was placed in a beaker surrounded by either tap water or 40% sucrose. We began the experiment by soaking the dialysis tubes to prepare them for the sucrose concentrations they would be filled with. Taking each bag, two were filled with 10mL of tap water, one filled with 10mL of 20% sucrose, one with 10mL of 40% sucrose and another with 10mL of 60% sucrose. Each bag was clamped closed. All the bags...
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