AP BIOLOGY

Detailed explanation-1: -Signaling molecules are often called ligands, a general term for molecules that bind specifically to other molecules (such as receptors). The message carried by a ligand is often relayed through a chain of chemical messengers inside the cell.

Detailed explanation-2: -Autocrines are long-distance chemical signals that travel in blood throughout the body.

Detailed explanation-3: -The simple gas nitric oxide (NO) is a major paracrine signaling molecule in the nervous, immune, and circulatory systems. Like the steroid hormones, NO is able to diffuse directly across the plasma membrane of its target cells.

Detailed explanation-4: -Endocrine Signaling: To send messages across long distances, cells use this method. Endocrine signals travel through the bloodstream to reach target tissues and cells. Signals that originate in one part of the body and travel to their target through the bloodstream are called hormones.

Detailed explanation-5: -Paracrine signaling acts on nearby cells, endocrine signaling uses the circulatory system to transport ligands, and autocrine signaling acts on the signaling cell. Signaling via gap junctions involves signaling molecules moving directly between adjacent cells.