Page 122 - The Miracle in the Cell Membrane

The Miracle in the Cell Membrane

pro tein struc tures pro duced spe cif i cal ly for for eign cells
enter ing the body. The sur face of a bac te ri um becomes
cov ered with anti bod ies "tai lor made" for itself. These
anti bod ies are bound to recep tors on the pha go cyte,
which pulls in the bac te ri um. At the con nec tion point, the
pha go cyte's mem brane col laps es in on itself in less than a
sec ond and com plete ly enfolds the par ti cle. Increasingly,
a great er num ber of recep tors are bound. All these events
take place sim i lar to a zip per's being done up. As the
mem brane clos es, it lit er al ly forms a pock et. Then, pro -
teins in the inter nal cell fluid con tract and pull the pock -
et into the cell, after it is left free inside the cell.
How did the pha go cyte cells come to assume the
respon si bil i ty of com bat ing harm ful sub stan ces, while
almost all cells draw both nec es sa ry and use ful sub stan -
ces into them selves? How did they arrive at imple ment -
ing this proc ess, known as pha go cy to sis, in con trast to
other cells? How did they devel op the lysos o mes that
frag ment with in the cells the sub stan ces they have swal -
lowed? How does this frag ment ing sub stance—the lyso -
some—know that it must destroy harm ful bod ies and not
the cell itself? Who decides that a body is harm ful, and
how? In short, how did the cell acquire the knowl edge
with which to iden ti fy and destroy ene mies? As you
watch a bruise or infec tion in your body heal with out
your doing any thing, your cells pro tect you from dan ger
with exceed ing ly ration al meth ods. It is not pos si ble for
them to have assumed such an impor tant respon si bil i ty
on their own and then to imple ment it with such great
expert ise.

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