Page 117 - The Miracle in the Cell

HARUN YAHYA

CLOSED Gate OPEN

External
environment
Cell
membrane

Cytoplasm
Hydrophobic Hydrophobic
surface surface
Ion-selective filter

Figure 6.5
The cell membrane channels, in their open and closed state. It is not
known what decides whether these channels stay open or closed.

Outside
the cell
Solution
Channel
proteins Figure 6.6

Outer membrane In some cells, exchange of
materials takes place in a
number of stages. The dia-
gram shows how a bacteri-
al cell's double-layered
Space between two membranes solution it binds to protein passing through the chan-
The periplasmic
membrane takes up a
Free periplasmic
substrate binding
substrate binding
protein and the
solution. The solution
nel proteins in the first
membrane is captured by
a periplasmic substrate
protein, found in the
periplasmic space. The
protein/solution complex
attaches to a selectively
Transport protein
permeable gate in the sec-
ond membrane. Changes
taking place in the pro-
Inner membrane tein's structure allow the
solid substance to pass
through the selective gate.
With the energy acquired
from a process known as
ATP hydrolysis, the sub-
stance is taken into the
cell.

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