Pieces of Bridges

The semi-coherent and hopefully sometimes educational ramblings of a ridiculously geeky biochemistry student.

Learn amino acids with Olivia: But… why?

Ok, so I figured that seeing as I’m making posts with information about every amino acid it might be helpful to provide some information as to exactly what amino acids are and why they are important. I mentioned this briefly before but I wanted to do a bigger thing on it. 

Basically, amino acids are the building blocks of proteins. And proteins make up pretty much everything in your body. Muscle fibres are made up of two proteins, actin and myosin, hair is made up of keratin, proteins called enzymes are responsible for every metabolic process in your body and so on. So, how do amino acids get turned into proteins? 

Step one- the primary structure

Two processes called transcription and translation convert the information stored in DNA into a long string of amino acids bonded together by a peptide bond. This bond occurs between the amine group of one amino acid and the carboxylic acid group of another. The chain formed is known as a polypeptide chain.

Step two: Secondary structures

Interactions known as hydrogen bonds occur between the backbones of amino acid residues in the polypeptide chain (the backbone is all the parts of the amino acids that are not the side chains) and these can result in one of two structures: an alpha helix or a beta pleated sheet. 

Beta pleated sheets are generally quite strong and rigid while alpha helices are more springy, as their appearance might suggest. Alpha helices have the side groups projecting outwards from the spiral as many of the groups are too bulky to fit on the inside. 

Step three: the tertiary structure

After the protein has formed alpha helices and beta pleated sheets, interactions occur between the side groups of the amino acid residues that fold the protein up into its 3D conformation. These can be hydrogen bonds, Van der Waals interactions, hydrophobic interactions and dipole and/or electrostatic interactions and sulphur bridges between some amino acids. While these interactions are individually nowhere near as strong as the peptide bonds making up the polypeptide chain, together they can hold the whole protein together- provided the temperature or pH does not increase or decrease too much from the optimum range for the body. 

(an example of a protein. Proteins can come in a wide variety of shapes and sizes in organisms according to their different functions.)

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