Biology

The correct answer is: A.They require a receptor on the cell membrane to initiate signaling.

Explanation:

Protein-based hormones are hydrophilic (water-soluble), which means they cannot easily diffuse across the lipid bilayer of the cell membrane. Instead, they bind to receptors on the surface of the target cell. This binding triggers a signaling cascade inside the cell, often involving secondary messengers (such as cAMP or IP3), which ultimately lead to the desired cellular response.

Here’s why the other options are incorrect:

B."They bind to intracellular receptors inside the target cell": This is incorrect for protein-based hormones, which do not typically enter the cell. Instead, they bind to membra...