Question

what is juxtacrine signaling?
a type of signaling that occurs between adjacent cells
when cells physically touch and transfer signals through proteins on their surface
when cells transfer signals through the nervous system
a type of signaling where the signal molecule acts on the same cell that released it
a type of signaling that involves the release of hormones into the bloodstream

Explanation:

Juxtacrine signaling is a form of cell - cell communication. It specifically occurs when cells are in direct physical contact. In this type of signaling, the signal is transferred through proteins on the surface of the cells. For example, in some developmental processes, adjacent cells use juxtacrine signaling to coordinate their activities.

• Option 1: While it is true that it occurs between adjacent cells, it is more specific than just "a type of signaling between adjacent cells" as it involves surface - protein - mediated transfer.
• Option 2: This is the most accurate description as it highlights the key feature of physical touch and surface - protein - mediated signal transfer.
• Option 3: Transfer through the nervous system is not juxtacrine signaling. Juxtacrine is a local, cell - to - cell (in contact) mechanism, not a nervous - system - based one.
• Option 4: A signal acting on the same cell that released it is autocrine signaling, not juxtacrine.
• Option 5: Release of hormones into the bloodstream is endocrine signaling, not juxtacrine.

Answer:

When cells physically touch and transfer signals through proteins on their surface