Diffusion and Osmosis

Topics: Cell, Cell biology, Cell wall Pages: 9 (3022 words) Published: December 1, 2012

In this Diffusion and Osmosis lab a total of three experiments were performed. For experiment 5.1 we investigate diffusion through a selectively permeable membrane and the many factors that influence the rates of diffusion. In experiment 5.2 we investigate both animal and plant cells in different molar solutions and the different osmotic behaviors within the cells. In experiment 5.3 we test the osmolarity of plant cells through the usage of potato tuber cells. In experiment 5.1 in order to observe diffusion we examine the Brownian movement by observing carmine on a wet mount slide, and by using dialysis tubing, we investigate the selective permeability to reducing sugar, glucose, starch, and iodine potassium iodine. In experiment 5.2 we use samples of ox blood and Elodea plant to observe the net flow of water from the surrounding solution into the cells. In experiment 5.3 in order to estimate the osmolarity of the potato tuber cells we use the methods of change in weight and change in volume. In experiment 5.1 while observing the wet mount, the Brownian movement of the carmine particles are never ending and show no pattern. While investigating the permeability of the dialysis tubing through the Benedict’s test, the solution inside of the bag (glucose), was originally clear, but after the Benedict’s test turned a strong orange color, finally ending with a final color of dark blue-black. In experiment 5.2 while observing the ox blood under the microscope the cells underwent either lysis or shriveled up. When observing the Elodea cells in distilled water and separately in salt water, the appearance and condition of the cell drastically changed. When the Elodea cell was placed into the distilled water, the cell became swollen and underwent lysis. However, when the Elodea cell was placed into salt water, the cell shriveled up and appeared bumpy. In experiment 5.3 when placing the potato segments into different molarities of sucrose a trend appeared. With a higher sucrose molarity, the potato segment gained less and less weight until eventually, the potato lost weight. In experiment 5.1, using this information we discovered from the wet mount, we concluded that smaller particles move more rapidly than larger particles. In the dialysis tubing experiment we determined from the color changes in and outside of the bag that iodine and glucose are smaller particles able to pass through the tubing, while the starch is unable to do so because of its larger particle size. Iodine was absorbed into the tubing, turning the solution into the resulting blue-black color. In experiment 5.2 we determined that when the animal cell is placed in a hypertonic solution, water left the cell making the cell shrivel up and appear bumpy, or crenate. However, when the animal cell is placed in a hypotonic solution, water enters the cell and undergoes lysis, making the cell swell and eventually burst. When observing the Elodea plant, we determined that the distilled water was the hypotonic solution and the salt water was the hypertonic solution and had a higher OAS. We determined that the preferred way of living for plant cells is in either an isotonic or hypotonic environment. In experiment 5.3 we determined that as the sucrose molarity increases, less weight is gained by the potato, until eventually, the potato segments lose weight and their percent weight change becomes negative. Introduction

In this lab, we observe the process of diffusion and osmosis. In the process of diffusion, molecules spread from an area of higher concentration to an area of lower concentration. When the molecules are even throughout the area, this is called equilibrium. Osmosis is the diffusion of water across a membrane. In osmosis water will move towards the higher concentration of solute. Diffusion and osmosis are both type of passive transport, meaning that no energy is required for the molecules to move into or out of the cell...

References: * Lodish, H; Berk, A; Kaiser, C; Scott, M; Ploegh, H, Bretscher, M. 2007. Molecular Cell Biology, Freeman, United State of America.
* Wayne, R. 2009. Plant Cell Biology: From Astronomy to Zoology, Academic Press, United States of America.
* Lewis, M. 1997. Diffusion, Osmosis, and ATP. Pp. 176-182 in Mallinson, J et al. eds, Integrated Science: Horizons (6th edition), Ginn, New Jersey.
* Miller, S. 2006. Animal Cells and Their Function. Pp. 126-148 in Castro, B et al. eds, Zoology (7th edition). McGraw-Hill, Texas
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