AP BIOLOGY

Detailed explanation-1: -Gap junctions in animals and plasmodesmata in plants are connections between the plasma membranes of neighboring cells. These water-filled channels allow small signaling molecules, called intracellular mediators, to diffuse between the two cells.

Detailed explanation-2: -Juxtacrine signalling is a type of cellular communication between contacting cells, for example by means of gap junctions that allow for signalling molecules to pass from cell to cell. This type of interaction can be transitive, allowing distant cells to communicate with each other by successive cellular contacts.

Detailed explanation-3: -In biology, juxtacrine signalling (or contact-dependent signalling) is a type of cell–cell or cell–extracellular matrix signalling in multicellular organisms that requires close contact. In this type of signalling, a ligand on one surface binds to a receptor on another adjacent surface.

Detailed explanation-4: -Juxtacrine signaling occurs between neighboring cells that are in physical contact with each other. In this case, the signaling molecule is not free, but is instead bound to the membrane of the cell. It may then interact with a receptor on the membrane of an adjacent cell.

Detailed explanation-5: -Paracrine signaling involves the secretion of specific signaling factors by one cell which are perceived by corresponding receptors on another cell in the vicinity, triggering a response in it9, 10, whereas juxtacrine signaling requires direct contact between cellular components of the two cells involved11, 12.