The biochemistry of cell: information delivery (Introduction)

by David Turell , Thursday, April 25, 2019, 19:45 (2038 days ago) @ David Turell

The new information has to get through cell membranes:

https://phys.org/news/2019-04-cell.html

"The interior of all living cells is separated from the outside world by membranes. These membranes keep the cells intact and protect them from negative influences. But they also act as a barrier for nutrients and information. For this reason, cell membranes contain mechanisms that enable selective access to desired substances or transmit information from external signals into the cell.

"An important signal pathway in mammals consists of three components: The first is a receptor that recognises the signal and is activated by it. The second is a so-called G protein that binds to the activated receptor and transmits the signal to one or more effector proteins. In this case, the effector is adenylyl cyclase, the third component of the signal chain. This protein is activated by a subunit of the G protein and produces, in a biochemical reaction, a secondary messenger called cyclic AMP (cAMP).

"cAMP triggers various reactions in the cell; for example, it increases the permeability of the membrane to calcium in cardiac cells, leading to an increase in the heart beat rate.

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"'Surprisingly, in determining the structure of the adenylyl cyclase bound to the alpha subunit of the G protein, we discovered that the protein appears to be able to inhibit itself," says Korkhov. One part of the protein is responsible for this self-inhibition. This part blocks the active site of the enzyme and prevents the overproduction of cAMP.

"This new insight into the molecular structure of adenylyl cyclase provides a much better understanding of how external signals lead to the controlled production of the important secondary messenger cAMP. "

Comment: In this case the stimulus to the cell is meant to initiate a specific required reaction and a series of specific molecules, one of which is especially designed to employ inhibition. The research makes it clear the cell is obviously programmed to make the proper response, no innate intelligence necessary.