Question

How would you order different mechanisms of signaling in a cell from fastest to slowest?

____ is probably the fastest, followed by ____ and, lastly, ____.

Answer 1

Cell signaling is a means by which cells communicate with each other for carrying out and coordinating basic cellular activities and actions. Cells perceive signals through receptors and accordingly respond to the microenvironment. A cell can communicate signals to other cells in various ways. Direct signaling involves transfer of ions from one cell to other through pores in the membrane. Those pores are made up of membrane proteins and are called gap junctions. This is considered as the fastest mode of cell-cell communication and occurs where fast and well-coordinated activity of cells in required. Example- The muscle cells in the heart communicate with each other via gap junctions which help in their contraction at a faster rate. Other signaling mechanisms such as endocrine or paracrine involve release of chemicals that affect the behavior of target cells.

               Signaling between cells located at distances. Paracrine signaling involves participation of cells located in the same tissue, while autocrine signaling affects the cell that produced it. Endocrine signaling involves cells located in separate organs and tissues. Blood stream transports the signaling molecule between organs. Interactions between proteins on the surfaces of Cells trigger changes in cell behavior after interacting with proteins present on the surface. in neurotransmission, neurons interact with their target cells with the help of specialized cells called neurotransmitters.

             The effects of a signaling molecule can be fast or slow. Fast responses usually involve changes in the activity of proteins (muscle contraction, fusion of secretory vesicles, changes in metabolism), whereas slow responses require synthesis of new proteins. Fast responses are transient while slow responses cause long-term or permanent changes in cell behavior.

In some cases, activation of receptor is caused by a ligand while for other cell surface receptors the ligand interaction is not required for cell's response. The activated receptor interacts with proteins inside the cell and changes the cell's behavior. The set of changes induced in a cell by receptor activation is called a signal transduction mechanism. The pace of the signaling depends upon the type of molecule receptor interacts with.

                   In Notch-mediated signaling, activation of Notc causes the Notch protein to be altered by a protease. The release of Notch protein from the cell surface helps in changing the cell behavior. In other pathways, protein–protein interactions inside the cell stimulate the cell behavior cells to progress. The phosphorylation of receptor generates binding site for a protein and thus induce protein–protein interaction. Binds of the ligand to the receptor activates the receptor to phosphorylate it. Signaling transduction pathways respond differently depending on the amount of signaling received by the cell.