Final answer:
All GPCRs possess similar structures with the presence of secondary structure, including alpha helices and beta sheets.
Step-by-step explanation:
All GPCRs (G-protein coupled receptors) possess a similar structure, with an important feature being the presence of secondary structure. Secondary structure in proteins refers to the folding of the amino acid chain into specific patterns. The two common types of secondary structure found in GPCRs are alpha helices and beta sheets.
Alpha helices are spiral-shaped structures formed by hydrogen bonding between amino acids, while beta sheets are formed by side-by-side arrangements of amino acids also held together by hydrogen bonds.