Page 136 - The Miracle in the Cell Membrane

The Miracle in the Cell Membrane

ni zing, as if they were refer ring to a con scious sys tem. Certainly
the com po nents com pris ing the cell—atoms, amino acids, pro -
teins—are all uncon scious, what ev er their size and func tion. Yet
the emerging mech a nism evi den ces con scious activ i ty. This
supe ri or Intel lect we encoun ter belongs to our Almighty Lord,
the Creator of all things, Who per vades all pla ces.

Sensitive Selection by Ion Channels

The cell mem brane is select ively per me a ble for ions, and for
many other sub stan ces. (Ions are atoms or mol e cu les that carry
an elec tri cal charge, hav ing lost or gained an elec tron.) In addi -
tion to the cell mem bra ne's phos phol i pid struc ture, it also repels
ions in the extra cel lu lar fluid. Therefore, ions can enter or leave
the cell only by way of the spe cial pro teins in the cell mem brane.
However, ions do not pass at ran dom along these pro tein chan -
nels: The chan nels behave most select ive ly on which ions will
pass.
Ions are gen er al ly mobile, in order to bal ance their elec tri cal
char ges. In any solu tion under typical con di tions, there are as
many neg a tive ly charged ions as pos i tive ly charged ones. So
long as this equi lib ri um is not dis rupt ed, no poten tial dif fer ence
in charge aris es. (Potential dif fer ence is the dif fer ence in elec tri -
cal ten sion between two points.) If that equi lib ri um is dis rupt -
ed, the + and – charged ions in the solu tion will move in order
to keep the solu tion neu tral.
The pas sage of ions through the cell mem brane takes place
via this mech a nism. Since the con tent of the intra cel lu lar fluid is
dif fer ent from that out side the cell, ions cross over in order to
restore equi lib ri um between these flu ids. The chan nels by

134