Passive Transport
Ch5 Section 6
Passive Transport
movement of substances
across the cell membrane
that does not require
energy.
1. Diffusion
O movement of substances from
an area of greater concentration
to an area of lower
concentration.
O substances diffuse down their
concentration gradient.
1A. Osmosis
O the diffusion of water through a
selectively permeable membrane (cell
membrane).
O involves the movement of a substance
–water- down its concentration
gradient.
2. Facilitated Diffusion
O transport of substances through
a cell membrane using carrier
proteins.
The direction of water movement
across the cell membrane depends
on the concentration of free water
molecules in the cytoplasm and in
the fluid outside the cell.
There are three possibilities for the direction of
water movement.
1)
Water moves out ⇒ Cell
shrinks ⇒ Hypertonic
solution
The fluid outside the cell has a lower
concentration than the fluid inside the cell
(cytoplasm).
2)
Water moves in ⇒Cell Swells
⇒ Hypotonic solution
The fluid inside the cell (cytoplasm) has a lower
concentration than the fluid outside the cell.
3
) In and out at equal rates
⇒Cell Stays the same
⇒Isotonic solution
The cytoplasm and the
fluid outside the cell has
the same concentration.