Atichai Suwannapeng
Pre Lab #6
Diffusion, Osmosis, and Tonicity
Group #3
Section A3
Group Members: Laghu Shakya, Alex Maican, Kelvin Chen, Ziye Lin
10/18/2015

Abstract:
In this lab we will be gaining an understanding of how transport in membranes work. This is important because in our semi permeable cell membrane the mode of movement relies on transport. Some methods of transportation for molecules are simple diffusion, facilitated diffusion, active transport, exocytosis and osmosis. The reason molecules tend to move around when dissolved in a solution is because all molecules display random thermal motion and have kinetic energy. Kinetic energy is what allows the molecules to diffuse down a gradient of high concentration to regions of low concentration until the distribution of molecules become equal and achieved dynamic equilibrium. The entire solution only becomes homogeneous when one of the several factors are reached: the size of the dye molecules, temperature of the solution, density of the solvent and concentration of the dye. Heat is what causes random motion of molecules and passively moves molecules in biological systems. However, we can’t see this movement with our naked eye. In order for us to see this movement, we must use a microscope to see the small particles move after collision, this is called the Brownian movement. When talking about the cell membrane we must understand that it is selectively permeable, which means it can choose what can pass through the membrane and what can’t. Polarity and size are he two most important characteristics of molecules govern their passive movement through a lipid membrane. Dialysis tubing is what we are going to be using in our second procedure to model a selectively permeable membrane. Dialysis is the separation of dissolved substances by means of their unequal diffusion through a selectively permeable