Final answer:
The protein class of hormones are charged and water-soluble, preventing them from diffusing through the cell membrane. Thus, their receptors are located in the cell membrane, and the correct answer is (B) Charged, in the cell membrane.
Step-by-step explanation:
The protein class of hormones, which are typically peptide or amino acid-derived, are generally charged molecules. Due to their charged, water-soluble nature, they cannot readily diffuse through the lipid bilayer of the cell membrane. Instead, these hormones have their receptors located on the cell membrane, where they can bind without needing to enter the cell. Therefore, the correct answer to the question is 'Because of their charged nature, the protein class of hormones have receptors located in the cell membrane' which corresponds to option (B) Charged, in the cell membrane.
Hormones that belong to the protein class typically have receptors located on the surface of the cell membrane because they are charged and lipid insoluble. These hormones include amino acid-derived hormones and polypeptide hormones. They cannot diffuse through the plasma membrane and instead bind to cell surface receptors. This binding initiates a signaling pathway that triggers intracellular activity and carries out the specific effects associated with the hormone. For example, the amino acid-derived hormone epinephrine binds to its receptor on the cell surface, activating a G-protein and ultimately leading to a cellular response.