Proteins
Polymers of Amino Acids Vital to Biochemistry in the Human Body
Protein is one of the nutrients we must consume to stay healthy, but what is it and what does it do in the human body?
Proteins are polymers. This means that they are long molecules made up of chains of repeating units. The units in proteins are called amino acids and these are connected by many peptide links. Proteins are used in the body as enzymes (catalysts for important reactions), cellular structure, muscular functions and receptors for hormones all of which are important in the study of biochemistry. Without proteins life as we know it wouldn’t exist.
Amino Acids
There are twenty amino acids which are the building blocks of proteins in the human body. They are all based on a carboxyl group and an amino group joined to a central carbon with different units attached. They become large molecules when the amino group of one amino acid reacts with the carboxyl group on another to form a peptide bond with the loss of a water molecule.
Primary Structure
Proteins are very long chains of amino acids. A typical protein contains 200-300 units, although some have thousands. What makes proteins so versatile is the structure which has three different levels. The first level, the primary structure, is the sequence of amino acids. The body’s DNA contains all the information necessary for the synthesis of very protein the body will need.
Secondary Structure
With the sequence of amino acids we have a kind of necklace made from a chain with different “charms” hanging from each link of the chain. The chain is the back-bone of peptide bonds; the charms are the groups which determine the amino acids. Secondary structure is caused by interactions between the peptide bonds. A peptide bond has one C=O bond (carbon double bonded to oxygen) and one N-H bond (nitrogen bonded to hydrogen. The oxygen in the C=O bond is negative and the hydrogen in the N-H bond is slightly positive, so they can form hydrogen bonds between them (see article on water). Some sections of a protein molecule can role up and become a helix with the side groups pointing outwards. This is called an alpha-helix. Sometimes sections of the chain line up next to each other, connected by hydrogen bonds. This is called a beta-conformation.
Tertiary Structure
The protein chain also folds up into very complex structure, held together by interactions between the side groups. For example the side group of the amino acid called cysteine ends with a –SH group which forms a bond with another cysteine group further down the chain. There are also other hydrogen bonds which can form and other attractions between groups. This macro-structure determines the function of the protein. For example the way an enzyme protein folds up creates an active site with side units in exactly the correct configuration to cause an important reaction to take place.
Proteins are examples of the incredible complexity and accuracy necessary for the human body to function correctly.
