Page 104 - The Miracle in the Cell Membrane

The Miracle in the Cell Membrane

Molecules are in constant motion—but not random
motion, however. Molecules slide over one another in
liquids, move away from one another in gasses and
approach one another very closely in solids, but
never disrupt this order.

to a car ry ing pro tein. Molecules move in var i ous direc -
tions from the envi ron ment they are already in. This
move ment chan ges accord ing to wheth er the mol e cule is
a solid, a liq uid or a gas. Gas mol e cu les are more active
than ones in the liq uid or solid state.
Above the freez ing point of their par tic u lar sub -
stance, mol e cu les are in a state of motion and trans fer
their momen tum for ces when they strike anoth er object.
For that rea son, when you drop ink into pure water, both
the water and the ink become less con cen trat ed. The
cause of dilu tion is dif fu sion, because any mol e cule in
motion tends to push out, spread ing as far as it can. As
mol e cu les move apart, they become less con cen trat ed,
more dilute, more dif fuse. 35

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