Question

Which of the following is a characteristic of cell communication that suggests cell signaling evolved early in the history of life?

A. All organisms form cell junctions to allow transfer of signaling molecules.

B. All organisms produce hormones to carry out signaling processes.

C. Plants, animals, and bacteria share very similar signaling processes.

D. Plants, animals, and bacteria use long-distance signaling molecules.

Answer 1

Cell communicationis process by which cell sense the external environment of it by some signal by virtue of which it act or modify itself. It is a very important process through which cell can sense it's internal as well as external environment.Any change in extracellular environment initiate a signalling Cascade pathway inside the cell so that cell can take necessary steps to cope up with it.So this signalling pathway are very important for survival of the cell in any environment.That's why this type of mechanisms present from very primitive to most advanced organism also.

Now about the characteristics-

A. Most bacteria usually are single celled organism but they have cell signalling pathway by which they can sense the external as well internal environment. Like if there is deficiencyof nitrogen inside the bacterial cell, it will initiate nif gene transcription for acquisition of nitrogen from the environment by some signalling molecules present inside the cell which determine the nitrogen concentration inside the cell. So for the cell signalling cell junction is not essential.Also in multicellular organism also there is no need of cell junction in every cell signalling pathway like autocrine or paracrine cell signalling.In these case cell release their signalling molecules in their extracellular matrix and that signalling molecules go and bind to the receptor present in the cell membrane of other cell. So cell junction is not a  characteristic early evolution of cell signalling.

B.All organism don't produce hormone for cell signalling.Hormones are mostly available in higher organism like animals and plants.Bacteria do not produce any hormone for cell signalling So it is also not a characteristics.

C.Yes. In all these organism the basic structure of signalling pathways are very similar. In most of the cases signalling molecules come and bind to the extracellular domain of the receptor which induce some conformational change in that receptor which leads to the formation of secondary messenger inside the cell which in turn induce some other adapter molecules and transcription factir.All these internal change of cell leads to activation of some transcription or chemical change to form necessary enzyme which help the cell to respond to that signal.So this is a characteristics of cell communication that suggest cell signalling is evolved early in life history.

D.No. every organism do not produce long distance signalling molecules. Endocrine Hormones in case of animals and plant hormones are only act on other parts of the body from where they are secreated. But is case of bacteria there is no hormone. Also in case of plants and animals there are lots of signalling molecules which are secreated locally like autocrine and paracrine hormone. So long distance signalling molecules is not a characteristics of early evolution of cell signalling pathway I'm cell communication.