Question

29. Differentiate between the four possible levels of a protein. Include the bonds involved and what part(s) of the amino acid are involved. a. Primary structure b. Secondary structure c. Tertiary structure d. Quaternary structure

Answer 1

A protein consists of a long chain of "building blocks", called amino acids There are 21 different amino acids which can be mixed and matched to obtain different proteins. Proteins can be hundreds of amino acids long In biochemistry, we call the linear sequence of these amino acids the "primary structure" of a protein The primary structure is a long, straight, chain of amino acids. However, in practice, some amino acids (that are non-adjacent) will bind together and form hydrogen bonds with one another This creates a "secondary structure" within the protein. Rather than forming a straight line, the secondary structure consists of planar "sheets (called beta-sheets) or "spirals" (called alpha-helixes). This increases the integrity and stability of the protein. These different secondary structures are still relatively elongated and will be organised even further in a third step This elaborate "folding" of the protein is called its "tertiary structure". Because each amino acid is different in terms of size, charge, and molecular composition, they tend to clump up and create "pockets" where they are most comfortable. Because of this tertiary structure, proteins will have a distinct shape In some cases, multiple distinct proteins may bind together and form a fourth structure called the "quater nary protein structure". In short Primary: Amino acid sequence Secondary: Helices or beta-sheets Tertiary: The folding of the protein due to forces between AA R-groups (e.g. disulfide bridges) Quaternary: Association of protein sub-units (e.g. hemoglobin has four sub-units)