Page 112 - The Miracle in the Cell Membrane

The Miracle in the Cell Membrane

tions. Glucose and most amino acids pass through the
mem brane by means of facil i tat ed dif fu sion. 38

Osmosis
Water dif fu sion is known as osmo sis—the pas sage of
liq uid mol e cu les through the semi-per me a ble mem brane
from a denser envi ron ment to a less con cen trat ed one. In
liv ing things, the closed envi ron ment is the cyto plasm,
con tain ing such sub stan ces as organ ic acids, sug ars, and
organ ic and inor gan ic salts, bound ed by the cell mem -
brane. Passage between the two envi ron ments takes
place accord ing to the dif fer ence in den si ty between the
cyto plasm and the exter nal envi ron ment, and this pas -
sage con tin ues until fluid con cen tra tion reach es equi lib -
ri um.

Osmotic
pressure
Glucose
Water

Selective permeable membrane
Diffusion of water
Water movement in less pressure
Osmosis is the passage of liquid molecules through the semi-permeable mem-
brane, from a dense environment to a less dense one. The cell membrane forms
a barrier between the intracellular fluid (cytoplasm) and the extracellular environ-
ment. Water passes through the cell membrane depending on the density differ-
ential between these two environments, and this flow continues until the fluid
concentration reaches equilibrium.

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