Glucagon, a peptide hormone, is upregulated when blood sugar levels are low. Which molecules in or on the plasma membrane would enable a cell to respond to glucagon and initiate its effects?

Answer;

D. receptor proteins

Explanation;

-Hormones bind with receptors to initiate the cellular response to a chemical signal. Target cells convert the signal into a biochemical change inside the cell. This is done via second messenger systems and also via direct gene activation.

-Receptors are complex proteins that only respond to specific hormones. Receptors for water-soluble hormones are found on the plasma membrane while receptors for lipid-soluble hormones are found in the cytoplasm or the nucleus. Receptors will down-regulate and decrease sensitivity when there is prolonged exposure to high levels of a hormone and also they have the ability to up-regulate and increase sensitivity in response to sustained low levels of a hormone.