Page 188 - The Miracle in the Cell Membrane

The Miracle in the Cell Membrane

sage to the recep tor anten na and the for ward ing of that
mes sage to the cell nucle us—this all takes place exceed -
ing ly quick ly.
To achieve the nec es sa ry speed, many hor mones
form sec ond ary mes sen gers with in the cell. For exam ple,
when a hor mone in the G pro tein sys tem reach es the cell
sur face, it attach es to a recep tor and sends a sig nal to a G
pro tein inside the cell mem brane. That G pro tein, acti vat -
ed accord ing to its type, either increas es or redu ces the

THE INTERCELLULAR COMMUNICATION THAT
THE INTERCELLULAR COMMUNICATION THAT
ASTONISHES SCIENTISTS
ASTONISHES SCIENTISTS
A great miracle can be seen in the harmony between the transmitter
and the receptor, how the message finds the receptor without losing
its way, the way the message means something to the receptor, and
how the cell immediately acts on the message.
The role of the G protein: (a)
Extracellular a) A hormone attaches to a
cell Hormon receptor on the cell mem-
G protein brane. The hormone-recep-
tor complex attaches to a G
Cell Membrane Receptor ( protein. (b) GTP replaces
GDP on the G protein. The
Adenylate cyclase G protein undergoes a
Intracellular fluid GDP
change of shape, making it
possible for the protein to
attach to adenylate cyclase.
Adenylate cyclase is activat-
Intracellular b) ed and ensures the transfor-
fluid
Hormon mation of ATP into AMP.
G protein
A series of chain reactions
Cell mem-
brane Receptor ( then follow, and these reac-
tions lead to a number of
changes inside the cell. The
Adenylate cyclase
Intracellular fluid GTP G protein is closed with the
transmission of the mes-
sage, and the reaction
comes to an end.

186