Experiences

Levels of organization of the protein molecule

Nevenka Kostova

Bulgaria

High Secondary School

Chemistry

Teaching in class

Direct

Sheet of paper is folded into a fan. On the composed thin sides are written arbitrary functional groups of protein molecules. In the inner parts of the so formed angles of the fan are also written functional groups that are close to each other when the sheet unfolds. Unfolded sheet represents the primary structure of the protein.
The closely located functional groups form hydrogen links and cause the folding of the polypeptide chain in the space.
At the beginning the sheet is unfolded (primary structure), closest functional groups form hydrogen links. This causes the folding of the polypeptide chain (secondary structure) - the sheet is folded into a fan. In this case the functional groups at the edges of the sheet, which at the beginning were remote, now converge and this leads to the formation of new hydrogen links between them, which causes a further folding of the protein molecule in the space (tertiary structure) - the sheet is crumpled with hands to form a ball, which corresponds to the globule.
For clarification of the quaternary structure of the proteins it is used one more sheet or more (or more) and it is made of a larger ball from all sheets, where each sheet is a single polypeptide chain. In the quaternary structure of proteins two or more polypeptide chains connect through weak links.