Page 101 - The Cell in 40 Topics

hen any organ wishes to produce a given protein, it sends
a message to the cells. When the "messenger" molecule
reaches the cell, it attaches to the antenna on the cell membrane. During
this bonding, it transmits the message it carries by its very presence to the
antenna, which then forwards the information it has received to its "tail" in
the interior of the cell. The antennas, which at the outset were in a single
state, now come together in paired groups. Enzymes in the body region
alter the shape of the tail section by adding phosphate to it, in a process
known as phosphorylation. All these processes are to summon the proteins
in the cell known as communication molecules (Figure 81).
Several molecules and proteins provide technical support for this sys-
tem. At this stage, molecules known as GTP—and those proteins referred
to as G for short—have an important effect. If the system is to function ef-
fectively, it is vital that several factors all enter into play at the right mo-
ment (Figure 82).

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