The four levels of protein structure are distinguished from one another by the degree of complexity in the polypeptide chain. A single protein molecule may contain one or more of the protein structure types: primary, secondary, tertiary, and quaternary structure. 1. Primary Structure: describes the unique order in which amino acids are linked together to form a protein.
2. Secondary Structure: refers to the coiling or folding of a polypeptide chain that gives the protein its 3-D shape. There are two types of secondary structures observed in proteins. One type is the alpha (α) helix structure. This structure resembles a coiled spring and is secured by hydrogen bonding in the polypeptide chain. The second type of secondary structure in proteins is the beta (β) pleated sheet. This structure appears to be folded or pleated and is held together by hydrogen bonding between polypeptide units of the folded chain that lie adjacent to one another
3. Tertiary Structure: refers to the comprehensive 3-D structure of the polypeptide chain of a protein.
4. Quaternary Structure: is the structure of a protein macromolecule formed by interactions between multiple polypeptide chains. Each polypeptide chain is referred to as a subunit. Proteins with quaternary structure may consist of more than one of the same type of protein subunit.
The correct answer is c. Postpartum psychosis is an extreme mental illness in which a new mother does not respond well emotionally to her new baby. This is not a voluntary disorder, which cancels out the first multiple choice option, and mothers who have diabetes actually seem to be protected from it, invalidating the second multiple choice option. The fourth multiple choice option seems to better describe postpartum depression, which is not the same as postpartum psychosis (the former is a depressive disorder, while the latter is a bipolar one).
