Diffusion

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Diffusion
Osmosis
Active Transport
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Aim How do materials enter and leave the cell?
I. Cell Membrane materials must cross the
membrane to enter and leave the cell.
A. Two ways materials enter and leave the cell.
1. Diffusion - is the movement of molecules from
an area of higher concentration to an area of
lower concentration. No energy is required.
Passive Transport
a. Osmosis is the movement of water molecules
from an area of higher concentration to an area
of lower concentration.
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b. Concentration Gradient - The difference in the
concentration of molecules across a space (on
either side of the cell membrane).
c. Equilibrium when there is a balance of
molecules on either side of the cell membrane.
There is no more concentration gradient.
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2. Active Transport when molecules go from an
area of low concentration to an area of higher
concentration. Energy is needed because the
molecules are going against the concentration
gradient.
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