Basic Science #4: Amino acids as building blocks for proteins.

Amino acids are the basic building blocks of proteins.  Proteins can be very complex, up to thousands of amino acids attached to each other in a chain to make a protein.  Here is a simple amino acid: Alanine.  As I showed you it has an amino group NH₂ which is basic (blue) in pH and a carboxyl group COOH which is acidic (red.)

Two amino acids are connected to each other in a peptide bond.  The next amino acid will be connected to the previous peptide via the carboxyl group, so that each chain of amino acids bound together will have an amino end and a carboxyl end.

To understand the complexity of proteins I will bring here a table of the 20 amino acids in life.  The names of the acids were given by the Greeks historically according to their source (like Serine was isolated from silk) or their color (Leucine for white.)  But it is more important to understand their diversity in structure. The position of the amino acid in the protein will determine how the protein will interact with its surroundings and what will be its activity. 

To envision this check the following table.  The amino acids are categorized in 5 groups.  First by their interaction with water: a hydrophilic amino acid  will be in a water environment and a hydrophobic amino acid (turquoise) will be in a fat environment as a cell membrane of a fat cell.

Next the hydrophilic amino acids can be polar but uncharged (grey.) They can be basic with two amino groups (blue) or acidic with two carboxyl groups (red.)

The order of the amino acids in the chain is just the primary structure of the protein.

The next level of complexity is the secondary structure, the way this amino acid chain twists and turns, as a helix.  Sometimes to the right, sometimes to the left and this is called a and b helix.

The next level is the tertiary structure, this is caused by bridges of bonds between two different parts of the protein.  These bridges are made with di-sulfide bonds between two amino acids that contain sulfur: Cysteines. 

There is a Quaternary structure as well by combining a whole folded protein with another similar (or different) sub-unit to make a dimer, a trimer and so on.  All the different possible combinations exist.  This is one way to show how we have such an amazing beautiful diversity in life!