Protein Digestion Design Lab. To detect the amount of protein molecules or short polypeptide chains in the cooked egg white for this experiment, the biuret reagent will be used.

Protein Digestion Design Lab

Introduction

It is known that the chemical digestion of protein occurs in the stomach and small intestine. Proteins are polymers of monomers known as amino acids (a monomer is one unit of amino acid) aligned in a genetically determined sequence. Proteins contains the elements carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur. The amino acids in a polymer are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code.

Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in virtually every process within cells. Many proteins are enzymes that catalyze biochemical reactions and are vital to metabolism. An enzyme is a biological catalyst made up of protein. It alters the rate of a chemical reaction without itself being chemically changed at the end of the reaction. Variables that affect enzyme activity include temperature and pH. There is a particular optimum temperature and pH which allow enzymes to perform most efficiently. This implies that since the structure of the enzyme can be affected by temperature and pH, enzymes must be proteins. When the bonds which give a protein its unique shape are broken, the protein, in this case an enzyme, is denatured.

Every enzyme functions most effectively at a specific pH. For example, pepsin, the protein-digesting enzyme secreted by the cells of the stomach lining, functions optimally at a pH of 2, depending on the substance being digested. On the other hand, trypsin, a protein-splitting enzyme secreted by the pancreas, functions optimally in an alkaline medium at a pH of 8.5, depending on the substance being digested. Most intracellular enzymes have pH optima near neutrality and do not operate successfully in an acid or alkaline medium. Furthermore, a major shift from the enzyme's optimal pH range may irreversibly inactivate the enzyme. Two protein-digesting enzymes are pepsin, secreted in the stomach, and trypsin, secreted in the pancreas. Trypsin is a component of pancreatin, along with pancreatic amylase and lipase.

To detect the amount of protein molecules or short polypeptide chains in the cooked egg white for this experiment, the biuret reagent will be used. The biuret test is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper(II) ion forms a violet-colored complex in an alkaline solution. The biuret reagent is made of potassium hydroxide (KOH) and hydrated copper (II) sulfate, together with potassium sodium tartrate. The reagent turns from blue to violet in the presence of proteins, blue to pink when combined with short-chain polypeptides.

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