When indirect signaling is used, the target cell responds to the signal when that chemical:

When indirect signaling occurs, the target cell responds to a signal when the chemical binds to a receptor. This process is a crucial aspect of cell communication, where signaling molecules, such as hormones or neurotransmitters, are released from one cell and travel to another. The binding of the chemical signal to specific receptors on the surface of the target cell initiates a series of intracellular events, often through signal transduction pathways.

These receptors are proteins embedded in the cell membrane that are specially designed to recognize and bind to particular signaling molecules. When a signaling chemical binds to the receptor, it causes a conformational change in the receptor, which then activates the associated signaling cascades. This can lead to various effects, such as gene expression changes, metabolic alterations, or physiological responses.

Understanding this mechanism illustrates how cells within an organism communicate, enabling coordinated responses to environmental changes. The other options, while related to cellular processes, do not directly characterize the mechanism of indirect signaling through receptors.