A previously unknown chemical signal is discovered in mice.Five observations about this signal are listed.Which observation would serve as evidence in distinguishing whether this chemical signal should be classified as a juxtacrine or a paracrine signal?
A) The signal molecule is a protein.
B) Cells responding to the signal have receptors specific to the signal.
C) Cells producing the signal are not affected by the signal molecule.
D) The signal molecule is not present in blood.
E) The signal molecule is not present in extracellular fluid.

Question

Quizplus · Accepted Answer

Juxtacrine signaling involves direct contact between the signaling and responding cells, often through membrane-bound molecules, whereas paracrine signaling involves the release of signals into the extracellular space, affecting nearby cells. The absence of the signal molecule in extracellular fluid (E) suggests it does not diffuse through this medium to reach target cells, aligning more with juxtacrine signaling mechanisms that do not rely on extracellular fluid for signal transmission.

A Previously Unknown Chemical Signal Is Discovered in Mice