1. PASSIVE TRANSPORT
One way cells maintain homeostasis is by controlling the movement of substances across their cell membrane.
Cells want to reach “equilibrium”.
Equilibrium – is a condition in which the concentration of a substance is equal throughout a space

2. Equilibrium:
Molecules eventually spread out so that they are evenly distributed.

3. Passive Transport
– the movement of substances across a cell membrane that does not require energy from the cell
***it does not require energy because substance are moving along or down the concentration gradient
concentration gradient – the
difference in the concentration
of a substance across a space

4. 1. Diffusion – the movement of a substance from an area of high concentration to an area of lower concentration
High Concentration
Low Concentration
(substance)

5. Which diagram(s) shows a concentration gradient?B. C. D.

6. 2. Osmosis – the diffusion of water through a selectively permeable membrane
ONLY water is allowed to move across the membrane.

7. 3. Facilitated Diffusion:
Transport Proteins allow molecules that
can’t pass the membrane by simple diffusion
to pass.
ex: ion channels – are a transport
proteins which allow ions to pass

8. Some transport proteins are referred to as carrier proteins because they bind to specific substances on one side of the cell membrane then carry the substance across releasing it on the other side. Also known as facilitated diffusion.

9. Passive Transport Examples
Osmosis
Carrier Protein
Transport Protein

10. The box is divided by a permeable membrane
The box is divided by a permeable membrane. In the blank drawing on the right, draw what the solution would look like once equilibrium has been reached.
A concentration gradient is present so particles will move from left to right.
To reach equilibrium the particles will move until they are equal on both sides.
Equilibrium 9 1 5 5

11. The square box indicates a cell membrane
The square box indicates a cell membrane. Use arrows to indicate the direction of diffusion.
is a solute that can pass through the cell membrane.
Cell membrane
inside
outside
11 inside; 6 outside

12. The square box indicates a cell membrane
The square box indicates a cell membrane. Use arrows to indicate the direction of diffusion.
is a solute that can pass through the cell membrane.
Cell membrane
inside
outside
6 inside; outside

13. Passive Transport Summary:
The movement of a substance down a concentration gradient, from high to low concentration, therefore NO energy is required from the cell!
Three Examples:
Diffusion (diffusion of any substance)
Osmosis (diffusion of water)
Facilitated Diffusion
(transport proteins or carrier proteins )