Protein Structure

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Proteins are reasonably large macromolecules comprised of one or more long amino acid chains. They are in every living organism and play a vital role in almost every biological process. They are involved in responding to stimuli, DNA replication, the transportation of molecules to another location, and they act as catalysts for metabolic reactions. In relation to protein structure it is much more complex than when we talk about the structure of smaller molecules because proteins have four different levels to their structure, these are primary, secondary, tertiary, and quaternary. There are twenty separate standard amino acids that cells use to construct protein. As their name suggests, amino acids contain an acidic carboxyl group and a basic …show more content…
Chains that have less than 50 amino acids in them are commonly known as peptides, while chains with more than 50 amino acids are referred to as polypeptides or proteins. A protein can comprised of one or several polypeptide molecules. The end of the sequence that has the free carboxyl group is known as the C-terminus and the end of the sequence with the free amino group is known as the N-terminus. The amino acids are all different based on their side chains which can give different structural, physical, and chemical properties to the protein. The amino acids all have one and three letter abbreviations given to them which are commonly used in science to simplify things. The amino acids can all be classed as either neutral, acidic, or basic depending on their side chain properties. Of all the twenty amino acids that are required to construct the proteins found in humans we are only able to synthesise ten of them in our bodies, the other ten are called essential amino acids meaning we must obtain these through our dietary intake. The sequence of amino acids determines the primary structure of the protein but the chemical and biological characteristics of the protein are highly dependent on the tertiary or three-dimensional …show more content…
There are two primary steps for the synthesis of proteins, these are transcription and translation. Protein synthesis starts off with transcription, the DNA code is transferred to messenger RNA in the nucleus of the cell. RNA polymerase creates a messenger RNA strand using the DNA as a template, this new messenger RNA moves through the nucleus to the cytoplasm. Messenger RNA associates with the ribosome subunits, and an enzyme in the cytoplasm activates its transfer RNA by attaching a specific amino acid to each transfer RNA. The first transfer RNA attaches to the P site of the ribosome and begins a sequence of building a protein using amino acids. The transfer RNA (or tRNA) carries an anticodon which is complementary to the codon on the messenger RNA (or mRNA) strand. For example, if the codon on the mRNA is AUG then the tRNA will have an anticodon UAC. Then the ribosome moves down the tRNA-mRNA complex. The first tRNA anticodon is now at the A site on the ribosome. A new tRNA complementary to the next anticodon in the sequence moves into the P site carrying the next amino acid, an enzyme in the ribosome catalyses the formation of a bond between the two amino acids now in the ribosome. Then the ribosome moves down the tRNA-mRNA complex again, the tRNA that was in the A site is now in the E site, and the tRNA that was in the P site is now in the A site. The
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