Effects of Alcohols on Membranes

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Beer’s Law is an empirical relationship that relates the absorption of light to the properties of the material through which the light is travelling. In turn, absorbance is proportional to concentration and the higher the concentration, the higher the absorbance. This experiment incorporated Beer’s Law and is focused on determining the stress that various alcohols have on biological membranes. Using five solutions of differing alcohol concentration for each of the three alcohols; methanol, ethanol, and 1-propanol and a small slice of beet, the stirred solution was placed into a plastic cuvette and then into a spectrophotometer and the absorbance of alcohol solutions were determined in order to conclude which alcohol and concentration of alcohol had the greatest effect on biological membranes. The results showed that the most non-polar of the alcohols being tested, 1-proponal, caused the greatest damage to the biological membrane, the beet cell’s vacuole. INTRODUCTION

The boundary between any cell and its environment is the plasma membrane, composed of a matrix of phospholipids molecules with many different kinds of proteins. Membranes have different properties and a variety of functions, in large part determined by the specific proteins within the membrane. The purpose of this experiment is to observe the effects of various alcohols on biological membranes, to determine the stress that various alcohols have on biological membranes and to conclude which concentration of alcohol has the greatest effect on biological membranes.

The central plant vacuole of plant cells contains water and solutes, including water-soluble pigments. Its membrane, the tonoplast, is normally poorly permeable to water. The central plant vacuole of the root cells of beet contains a water-soluble red pigment, betacyanin, which gives the beet its characteristic color. Since the pigment is water-soluble and not lipid soluble, it remains in the vacuole when cells are healthy. If...
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