The structure of proteins

Amino acids

Proteins are made of amino acids, which are bonded together by bonds called peptide bonds. The picture below depicts an amino acid.

As you can see, an amino acid consists of an amino group (NH2), a carboxyl group (COOH) and a variable, which is also called R. The variable is different in every amino acid, and this is why each of them is unique. 

The structure of proteins

The shape (conformation) of a protein determines what job it preforms. There are four levels of protein structure, all of them discussed and pictured below :).

PRIMARY STRUCTURE: The primary structure refers to the sequence of aminoacids in the protein. The amino acids are bond together by peptide bonds and thus form a long chain called a polypeptide chain. This chain of amino acids is an example of primary structure of a protein.

SECONDARY STRUCTURE: The secondary structure refers to a protein chain that is coiled up, either as alpha helix or beta pleated sheet (pictured below). The chain coils up because of the hydrogen bonds between the amino acids.

TERTIARY STRUCTURE: The tertiary structure is the three-dimensional (not just flat) conformation (shape) of a protein. It determines the specifity of the protein, and some factors that contribute to the tertiary structure are for example hydrogen bonds between R-groups, Ionic bonds between R-groups or disulfide bonds between cysteine amino acids.

QUATERNARY STRUCTURE: The quaternary structure refers to proteins made up of more than one polypeptide chains. An example of that is hemoglobin, which is essential in order to carry oxygen in our blood. 

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