Proteins
Protein is a complex chemical made up of a chain of units called amino acids. Proteins are the " worker bees" of the cell. They perform thousands of functions necessary for the survival of the cell. A string or chain of amino acids is called a polypeptide chain. There are 20 natural amino acids. A protein can have hundreds of amino acids connected in specific order. Proteins can be made of one or more polypeptide chain. 13 The sequence of nucleotides on the mRNA will determine the proteins built. The various arrangements of the four bases on the mRNA are grouped into bundles of three bases called codons, each codon decoded for particular amino acids.( see Figure 7) There are 4 3 or 64 codon variations that translate into the 20 amino acids. 14 Therefore, an amino acid can be coded in more than one way. For instance: The amino acid, leucine, can be coded in four different ways, CUU, CUA,CUG, and CUC (see Appendix). After a protein is made, it is folded and then does its job. There are special codons that signal the beginning and ending of a sequence of amino acids. For instance, a polypeptide sequences would begin with the codon, AUG and ending codons could be either, UAA, UGA, or UAG. 15
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