Diffusion/OsmosisDiffusion/Osmosis

Osmosis Diffusion Intro - YouTubeOsmosis Diffusion Intro - YouTube

Diffusion:Diffusion:

• Movement of molecules across a cell Movement of molecules across a cell membranemembrane

• Diffusion requires Diffusion requires NO ENERGYNO ENERGY• Molecules move from Molecules move from HIGHHIGH to to LOW LOW

concentrationconcentration..• Let’s see!Let’s see!• Let’s see MORE!Let’s see MORE!

Facilitated Diffusion

• Many cell membranes have special channels Many cell membranes have special channels (carrier proteins) that allow molecules to cross it.(carrier proteins) that allow molecules to cross it.

• These channels help or facilitate diffusion to These channels help or facilitate diffusion to happen.happen.

• This is known as This is known as facilitated diffusionfacilitated diffusion..• Like regular diffusion, will ONLY occur if there is Like regular diffusion, will ONLY occur if there is

a higher concentration of molecules on one side a higher concentration of molecules on one side of the membrane.of the membrane.

• Let’s see!Let’s see!

Osmosis

• Osmosis:Osmosis:

• Movement of Movement of WATERWATER from an area of from an area of more water (more water (HH) to an area of less water ) to an area of less water ((LL))

• Water moves OPPOSITE of all other Water moves OPPOSITE of all other molecules (i.e. solutes)!molecules (i.e. solutes)!

How does osmosis work?How does osmosis work?

• Across a SEMI-PERMEABLE membraneAcross a SEMI-PERMEABLE membrane• Only certain molecules, like water, can move Only certain molecules, like water, can move

freely across the membranefreely across the membrane

• Water molecules move from Water molecules move from HIGHHIGH to to LOWLOW• They want to BALANCE OUT a solutionThey want to BALANCE OUT a solution• Therefore, water moves OPPOSITE of other Therefore, water moves OPPOSITE of other

moleculesmolecules• Let’s See!Let’s See!

Example of Osmosis #1Example of Osmosis #1• Condition #1: More Water outside of cellCondition #1: More Water outside of cell

• Inside cell = Inside cell = 98% Water98% Water, 2% salt, 2% salt• Outside cell = Outside cell = 100% Water100% Water, 0% salt, 0% salt

Water moves into cell, salt moves out to balance

CELL SWELLS orCELL SWELLS orBURSTS!BURSTS!

Example of Osmosis #2Example of Osmosis #2• Condition #2: More water inside of cellCondition #2: More water inside of cell

• Inside cell: Inside cell: 98% Water98% Water, 2% Salt, 2% Salt• Outside cell: Outside cell: 95% Water95% Water, 5% Salt, 5% Salt

Water moves out of cell, salt moves in to balance

CELL SHRIVELS!CELL SHRIVELS!

Osmotic PressureOsmotic Pressure

• Cells behave differently when placed in Cells behave differently when placed in different solutions!different solutions!

• This is due to OSMOSIS!This is due to OSMOSIS!• Most cells are ~ 98% water!Most cells are ~ 98% water!

• Three types of osmotic pressure:Three types of osmotic pressure:• HypotonicHypotonic• HypertonicHypertonic• IsotonicIsotonic

Hypotonic ConditionHypotonic Condition• Cell is placed in 100% waterCell is placed in 100% water

• Solution outside of cell has Solution outside of cell has MOREMORE water, less of water, less of other materials (i.e., salt)other materials (i.e., salt)

• Therefore, solution is below strength (hypo)Therefore, solution is below strength (hypo)

98%

Water ENTERS cell100%

CELLSWELLS!

• Red Blood Cells in Hypotonic Solution - Red Blood Cells in Hypotonic Solution - YouTubeYouTube

Hypertonic ConditionHypertonic Condition• Cell is placed in 95% waterCell is placed in 95% water

• Solution outside of cell has Solution outside of cell has LESSLESS water, more of water, more of other materials (i.e., salt)other materials (i.e., salt)

• Therefore, solution is above strength (hyper)Therefore, solution is above strength (hyper)

Water LEAVES cell

98%

95%

CELL SHRINKS!

• Red Blood Cells in a Hypertonic Solution - Red Blood Cells in a Hypertonic Solution - YouTubeYouTube

Isotonic ConditionIsotonic Condition• Cell is placed in 98% waterCell is placed in 98% water

• Solution outside of cell has Solution outside of cell has SAMESAME water, same water, same amount of other materials (i.e., salt)amount of other materials (i.e., salt)

• Therefore, solution is equal strength (iso)Therefore, solution is equal strength (iso)

Water moves equally; Equilibrium exists

98%

98%

CELLSTAYSTHE SAME!

• Red Blood Cells in an Isotonic Red Blood Cells in an Isotonic Environment - YouTubeEnvironment - YouTube

Review of OsmosisReview of Osmosis

Isotonic, Hypertonic, Hypertonic Animation

You Tube Onion Cell Osmosis

Active Transport

• Sometimes, materials will move across the cell Sometimes, materials will move across the cell membrane membrane AGAINSTAGAINST a concentration gradient. a concentration gradient.

• LOW HIGHLOW HIGH• This is Active Transport.This is Active Transport.• THIS REQUIRES ENERGY!!! Just like pulling THIS REQUIRES ENERGY!!! Just like pulling

something uphill!something uphill!• Cells get this energy from Cells get this energy from ATPATP ( (AAdenosine denosine

TTriripphosphate)hosphate)