Page 171 - The Miracle of Hormones

The Zip Code System Within Cells

The shape of The SRP molecule that guides newly produced pro-
teins resembles a bowling pin.

Communication and Transportation in the Nucleus

It is known that a cell's nucleus contains a data bank (the DNA mol-
ecule) in which all physical characteristics are encoded in their smallest
details. Many operations within a cell are carried on with reference to the

information in the DNA. Therefore, between the nucleus and the cyto-
plasm and the various organelles there is heavy protein traffic at every
moment. This traffic and communication is organized to respond to the
needs of the cell.
The nucleus of the cell is different from other organelles; it is sur-
rounded by a double membrane. On this membrane are located en-
trance-exit complexes (Nuclear Pore Complexes) used by proteins. These
are entrance-exit complexes and not entrance-exit channels because of
their structure. Thanks to this special system, comparatively large
groups of molecules like RNA and DNA can pass through the nuclear
membrane so that the delicate structure of the protein and the molecules
are not damaged. When the entrance/exit complex is completely open,

they are ten times bigger than the channels in other organelles. Research
has shown that there are ten entrances and ten exits every second
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through each entrance/exit complex. The entrance and exit of a protein

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