Water Flow Across Cell Membranes

Topics: Concentration, Cell membrane, Red blood cell Pages: 6 (1529 words) Published: October 7, 2012

Lab Report 1
Water Flow Across Semi-Permeable Membranes


The movement of water across semi-permeable membranes as it relates to the laws of thermodynamics and energy flow with the diffusion of molecules down a concentration gradient of various solute concentrations, observing microscopically viewed outcomes, and spectrophotometrically measured results. ABSTRACT

This experiment will identify the movement and exchange of water through semipermeable membranes and the recognizable amount of cellular destruction possible as a result in this change of environment. Tested were different samples of mammalian red blood cells (RBC) which were microscopically analyzed and measured for absorbency rates with a spectrophotometer when introduced to the various solute concentrations of 0.6% salt (Na), 0.897% Na, 5.0% Na, and distilled water with a 0.0% Na solute concentration. My hypothesis is that cellular form and contents will either change or maintain form and consistency when introduced to these various different environments as osmosis occurs until a dynamic equilibrium has been reached between the membrane and its environment. It was found that when RBC’s are introduced to various solute concentrates their form and consistency did changed with highest amount of hemolysis evident in the distilled water 0% Na concentration with an absorbency rate of 2.091% and the lowest amount of hemolysis occurring WATER FLOW ACROSS CELL MEMBRANES pg.3 in the 0.897% Na or isotonic solution with an absorbency rate of 1.657%. Therefore it can be said that water will always move down its concentration gradient crossing semi-permeable membranes from a high concentration of water to a lower concentration of water.

In order for our cells to function properly they must be able to exchange substances into and out of the cell body through the cell membrane. This exchange is crucial to our existence and ability to maintain a constant state of homeostasis. This process takes place through either active transport with the use of cellular energy or passive transport requiring no cellular energy. In order for passive transport to occur the cell membrane must be semi-permeable to the substance or molecule in which it is transferring while preventing the transferring of unwanted molecules. This can be done through a process called diffusion. Diffusion is the movement of molecules from areas of high concentration to low concentration down a concentration gradient. In this experiment the diffusion process is the diffusion of water molecules. Molecules are always in constant movement balancing act or “dance” with each other to become equally distributed among both sides of the concentration gradient thus equaling a dynamic equilibrium which gives us a state of homeostasis or well-being. This is achieved when the concentration of molecules is equal in both areas where molecules will transfer. Often times a shift or disruption amongst the concentration gradient occurs and compromises the WATER FLOW ACROSS CELL MEMBRANES equilibrium of the cellular body and can cause cell damage. If two solutions have the same or equal solute concentrations it’s referred to as an isotonic solution. If one of the two solutions has a high solute concentration it’s referred to as a hypertonic solution. And finally if one of the two solutions has a low solute concentration it’s referred to as a hypotonic...
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