Biology Protein Lab Report

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Abstract

The objective of this lab was to measure the amount of protein from a piece of beef liver . This was done by taking the liver, blending it and then using a centrifuge to separate the supernatant from the pellet. Once that was completed, ammonium sulfate was added to the supernatant, chilled and then spun for a second time. Next, 20 mL of water is added to the pellet, stirred and the volume was recorded. The teacher calculated the total mass of liver to be 10.098g. Lastly a spectronic 20 at a wavelength of 540 nm is used to measure the absorbance of protein at different concentrations of the liver extract. The results for this showed that an absorbance of 540 nm, as the amount of liver extract increases, the absorbance increases.

Introduction

The main objective of this lab was to measure the amount of protein from a piece of beef liver, and then use the spectronic 20 to discover the concentration of protein found in the beef liver. “When a solution containing protein is saturated with a salt (ammonium sulfate, for example), the high salt concentration can alter the proteins‘ configuration (tertiary and quaternary structure) by competing with water for hydrophilic sites. Proteins are kept in solution normally by their hydrophilic interactions with water.” (43) When these interactions are disturbed, the molecules of protein change their shape and aggregate form a precipitate. I f the salt is taken out of the solution, the proteins will go back into the solution and sometimes return to their normal shape.

Salting out is the method of causing “proteins to form a precipitate in the presence of high concentrations of salt.” (43) Most proteins have a particular concentration of salt which can be used to form a precipitate. By increasing the concentration of salt in the liver it will slowly increase the amount of proteins that are salted out. After the proteins have been salted out and redissolved, they are assayed into different...
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