Cell Transport Mechanisms and Permeability: Physioex Laboratory Simulation on the Effects of the Rate of Simple Diffusion with Membranes of Varying Molecular Weight Cutoff, the Effects on Facilitated Diffusion of

Introduction

The special way that the plasma membrane of a cell is built enables it to bring materials that it wants into the cell or push things it doesn’t need out. Because of this unique property of selective permeability, transport of fluids, nutrients, etc. are possible either via passive transport or active transport. Passive transport is a type of transport process that does not require ATP energy, whereas it is a prerequisite in active transport. Diffusion and filtration are both types of passive transport processes, which rely on a concentration or electrical gradient, as in diffusion, or pressure, as in the process of filtration.

The first simulation will be testing the effects of membranes of differing molecular weight cutoffs (MWCO) on the rate of simple diffusion. MWCO is like the pore size of the membrane, which would restrict certain molecules too big to pass through. The solutes NaCl, urea, albumin, and glucose will be used to demonstrate diffusion through a 20, 50, 100, or 200 MWCO membrane. If the molecular size of the solute is too large, then it will be unable to diffuse through the smaller MWCO membranes, whereas if the molecular size of the solute is tiny, then it will be able to diffuse through any of the various MWCO membranes.

The second experiment will demonstrate the effects of glucose concentration and the number of glucose carrier proteins embedded in the plasma membrane on the rate of facilitated diffusion of glucose. Glucose, being a large molecule, needs to combine with carrier proteins in the membrane in order to transport down their concentration gradient. This process is called facilitated diffusion. The simulation will take either a concentration of 2.00 mM or 8.00 mM of glucose and let it diffuse through a membrane with either 500, 700, or 900 glucose carrier proteins embedded. If there is a more concentrated solution of glucose and a higher number of glucose carrier proteins, then there will be an increase in the rate of...