Membrane Permeability

Membrane Permeability

Introduction

The term used to describe the concentration of solutes in a given solution is tonicity. Three states of tonicity exist: hypotonicity, hypertonicity, and isotonicity. In a hypotonic solution, contains a greater concentration of impermeable solutes on the external side of the membrane. In a hypertonic solution, contains a lesser concentration of impermeable solutes on the external side of the membrane. In an isotonic solution, contain equal concentrations of impermeable solutes on either side of the membrane; this state is referred to as dynamic equilibrium.

Diffusion, dynamic equilibrium, is an important process that helps balance out particles inside and outside the cell. The plasma membrane defines the boundary of the cell. And membranes are semi-permeable and it allows certain substances in and out of the cell.

This lab determines the tonicity of Solution A sucrose, Solution B sucrose, Solution C methyl alcohol, and Solution D ethyl alcohol, Solution E propyl alcohol, and Solution F glycerol relative to a plant cell.

Methods and Materials

In this lab the actual concentrations of Solution A is 0.3M sucrose, Solution B is 0.6M sucrose, Solution C is 0.3M methyl alcohol, Solution D is 0.3M ethyl alcohol, Solution E is 0.3M propyl alcohol, and Solution F is 0.3M glycerol. The other materials needed for this lab are a compound light microscope, six slides, six slide covers, and six droppers.

The first step is to label A and B on two slides. Then cut two plant cubes at approximately 1.0 cm per side and place on each slide. Place two drops of Solution A 0.3M sucrose on the slide labeled A, and two drops of Solution B 0.6M sucrose on the slide labeled B. Then observe slide A with 0.3M sucrose solution and slide B with 0.6M sucrose solution under the microscope. Recorded the results and draw a pictures of the cells on the data sheet.

The second part of the experiment is to look at different alcohols. Follow the same procedures and label C, D, E, and F on four new slides for alcohols. Then cut four plant cubes at approximately 1.0 cm per side and place on each slide. Place a different alcohol group (Solution C 0.3M methyl alcohol, Solution D 0.3M ethyl alcohol, Solution E 0.3M propyl alcohol, and Solution F 0.3M glycerol) on each plant slide. Then observe slide C with 0.3M methyl alcohol, slide D with 0.3M ethyl alcohol, slide E with 0.3M propyl alcohol, and slide F with 0.3M glycerol solutions under the microscope. Recorded the results and draw a pictures of the cells on the data sheet.

Results

Originally, water entered and left the cell at the same rate in plants. After five minutes, Solution A's plant appears isotonic. And a hypertonic change occurred in Solution B's plant after five minutes. Solution C, Solution D, and