Answer:
recognizes a hormone’s chemical structure
Step-by-step explanation:
In living systems, chemical messengers called hormones are secreted into the body via the bloodstream or ducts by certain glands called endocrine glands e.g pancreas, hypothalamus etc. These hormones are meant to effect a physiological change in certain cells called TARGET CELLS.
In biology, a target cell is any receiving cell that has the ability to respond to signals and messengers like hormones. This responding ability of hormones is due to the possession of specific receptor sites for the specific hormones. The receptor on a particular target cell recognizes that specific hormone's chemical structure, hence, will only respond to it.
For example, an insulin hormone secreted by the pancreas will only be responded to by a target cell that recognizes the chemical structure of the insulin protein using its receptor molecule.