How does a proteins structure relate to its function?
A protein's 3D structure is largely determined by the primary sequence of the peptide.
First, the primary sequence detirmines the secondary structure of the protein, as groups that are located near one another on the chain interact to form local organized structures (mostly commonly: alpha-helices or beta-pleated sheets).
Furthermore, the primary structure of the peptide determines the tertiary and quaternary structure of the protein, since the R groups of amino acids will interact with each other and the environment. This leads to formation of larger non-localized structures. As a general rule in determining tertiary structure, polar, basic and acidic amino acids will all interact with one another or an aqeuous (water-rich) environment, while non-polar amino acids interact amongst themselves or a non-polar environment-such as a plasma membrane. This means that non-polar amino acids are generally found in the core of the protein where they help to maintain overall structure, while polar/ basic/ acidic amino acids are found either on the protein surface or in an enzymatical active site where they play a greater role interacting with and responding to the environment.
A protein's structure can relate to it's function in many ways, but consider these two points as an example. 1) Some proteins have a completely polar surface, which allows them to be suspended in solution, whereas other proteins have a region that is hydrophobic, as is the case with plasma-membrane associated proteins. 2) Some proteins (enzymes) have an active site where a chemical reaction on a substrate is catalyzed; if misfolded the protein's structure would be wrong and it would not complete the reaction.