Page 114 - The Miracle in the Cell

THE MIRACLE IN THE CELL

Oligosaccharide group

Recognition Channel
protein protein Transport Cholesterol
protein
Electron-
transport
proteins Receptor Phospholipid
protein
CELL SURFACE CYTOPLASM

Figure 6.2
Cell membrane of a pancre-
atic cell (right). In the
above diagram, the mosaic
model of this membrane is
magnified.

This thin layer-made up of unconscious molecules such as fats
and protein-carries out acts that we can consider intelligent.
To examine it in more detail, let's first look at the structure of the
cell membrane that can carry out so many processes. The membrane
is composed of a double layer of lipid molecules on both sides, facing
inside and outside. Located within these lipid molecules are "gates"
that facilitate entry into and exit from the cell, as well as receptors that
let the membrane recognize its external environment. These gates and
receptors, made from protein molecules, are located on the wall,
where they control all of the entry and exit from the cell with the
utmost care (see Figure 6.2).

Who Is in Control?

The cell membrane's main duty is to envelop the organelles with-
in it and hold them all together. But it also has a much more complex

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