Page 97 - The Cell in 40 Topics

odern-day telecommunications systems have been set up
using electronic and mechanical equipment and the most
advanced technology. Yet the communications systems inside the cell,
whose secrets have still not been unraveled, employ devices composed en-
tirely of protein. Instead of electronic circuits or semiconductors, as in our
mechanical devices, organic proteins contain carbon, hydrogen, oxygen
and nitrogen atoms.
Even so, the communications system established among cells resem-
bles those used by human beings in many respects. For example, there are
sensors analogous to antennas on the cell membrane that permit them to
understand the messages reaching them. Immediately beneath these an-
tenna are structures analogous to switchboard that decode the messages ar-
riving at the cells (Figure 77).
The "antennas" in question are located on the cell membrane,
1/100,000 millimeters thick, which surrounds the cell. Each receptor,
known as tyrosine kinase, consists of three basic sections, the head, body and
tail.

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