Biochemistry Laboratory Report

Biochemistry Laboratory Report 1
BIOCHEMISTRY LABORATORY REPORT
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Biochemistry Laboratory Report 2
INTRODUCTION
Protein Background
Proteins have diverse functions since they appear in unique and different structures. They
are macromolecules with a relatively high mass made up of one or more chains of polypeptides
which are composed of different amino acids as the primary building blocks. Cells usually use
twenty amino acids which are available in order to make the polypeptide chains of the proteins.
The amino acids are composed of elements such as nitrogen, carbon, oxygen, hydrogen, and
sulfur. Proteins always share and have similar molecular formula even though most of them
differ in the side groups they possess. Synthesis of proteins involves an enzyme that is located in
the ribosomes of a cell (Piana et al. 2015). It synthesizes proteins by joining the various amino
acids through condensation process where an amino group of an amino acid is joined to an acid
group of the other forming a respective peptide bond linking the carbon and nitrogen atoms of
two amino acids. The structure of a protein and its polypeptide chain is, therefore, very specific
due to the different chemical nature and shape of the amino acids which are involved in bonding
(O'sullivan et al. 2016).
Proteins always have different structural organizations which include the primary
structure which shows the aminoacid sequences in the polypeptide and it basically dictates the
biological function of the protein. This particular sequence is controlled mainly by genes
involved in translation which gives a particular order and the number of a protein’s amino acids,
the second structure level of proteins is the secondary structure which defines the specific shape
that amino acids take in the protein, the third structure level of proteins is the tertiary one which

Biochemistry Laboratory Report 3
defines the 3D structure of the protein which is shown by the bending and folding of the
polypeptide chains in the protein structure, the fourth level of structure of proteins is that of the
quarternary structure which involves the association between two or more polypeptide chains
(Ferreira et al. 2015).
Biuret Assay Background
This is a process that is used in the determination of the concentration of proteins. It is an
important and crucial technique used in most of the processes in protein assay procedures and
analysis including proteomics. Biuret assay reaction is used for both the qualitative and
quantitative analysis of proteins in terms of the peptide bonds which are available in the amino
acid structure bonding in the particular proteins (Liu & Pan 2017).
The principle of this essay revolves around spectrophotometry of color change on copper
ions in solution. A solution containing the proteins is treated with Cu2+ which is the cupric ions
in an alkaline conditioned medium. These ions react with the peptide bonds present in the protein
to form a purple-colored complex which is then measured using a spectrophotometer in a
quantitative analysis of the visible region (Rose, Funk & Neiger, 2016).
Cu2+ - peptide complex formed after the reaction