Cell Transport

Osmosis and Diffusion

Particles in constant motion Run into each other and randomly spread out

Particles move from an area of high concentration to an area of low concentration

Diffusion

Diffusion Can occur across membranes IF the particle

can cross the membrane

Does not require energy Passive transport

Time

Semipermeable

Facilitated Diffusion Molecules that can’t pass directly through

membrane may pass through a protein channel in membrane

Still no energy = passive transport

Osmosis Specific type of facilitated diffusion Diffusion of water through a selectively

permeable membrane

Is energy required?

Osmosis, cont’d Water moves from an area of high concentration to an area of

low concentration.

When comparing two solutions: Hypotonic – “below strength”; lower concentration of solute, higher

concentration of water Hypertonic – “above strength”; higher concentration of solute, lower

concentration of water Isotonic – “same strength”; solutions have same concentration of

solute and same concentration of water

Osmosis, cont’d Water moves from an area of high

concentration to an area of low concentration.

1 % salt99%

water

0% salt100%

water

In which direction will water move? Into the cell our out of the cell?

Water moves into cell(trying to reach equilibrium)

What will happen to the cell?

Is the solution hypertonic, isotonic, or hypotonic?

Hypotonic Solution

Osmosis, cont’d Water moves from an area of high

concentration to an area of low concentration.

1 % salt99%

water

5% salt95%

water

In which direction will water move? Into the cell our out of the cell?Water moves out of the cell.

What will happen to the cell?

Is the solution hypertonic, isotonic, or hypotonic?

Hypertonic Solution

Osmosis, cont’d Water moves from an area of high

concentration to an area of low concentration.

1 % salt99%

water

1% salt99%

water

In which direction will water move? Into the cell our out of the cell?No net movement of water!

What will happen to the cell?

Is the solution hypertonic, isotonic, or hypotonic?

Isotonic Solution

Active Transport Allows movement of particles against the

concentration gradient In other words, particles can move from low

concentration to high concentration

Proteins in membrane “pump” the molecules in or out

Requires energy Active transport

Passive vs. Active Transport