Transport Transport through the through the

Cell Cell MembraneMembrane

Fluid Mosaic Model

Review of the Types of Review of the Types of Membranes:Membranes:

1.1. PermeablePermeable

2.2. ImpermeableImpermeable

3.3. Semi-permeableSemi-permeable

1.1. PermeablePermeable ALL types of molecules can get ALL types of molecules can get

through, regardless of size or charge.through, regardless of size or charge.

Permeable Pavement – ever been to Kane County Cougar’s Stadium?

2.2.Impermeable Impermeable (non-permeable)(non-permeable)

NO molecules can get NO molecules can get throughthrough

3. 3. SEMI-SEMI-PERMEABLE !!!PERMEABLE !!!::

SOME SOME MOLECULES CAN MOLECULES CAN GET THROUGHGET THROUGH

– Very small or Very small or – Non-chargedNon-charged

Passive Passive TransportTransport

Does not expend Does not expend cellular energy for cellular energy for the movement to the movement to take placetake place– Ex-rolling down a Ex-rolling down a

hillhill

3 types:3 types:1.1. DiffusionDiffusion

2.2. OsmosisOsmosis

3.3. Facilitated DiffusionFacilitated Diffusion

1. DIFFUSION:1. DIFFUSION:Definition:Definition: Transport of molecules (in general)Transport of molecules (in general)

– From an area of higher concentration From an area of higher concentration to an area of lower concentrationto an area of lower concentration

– Until equal distribution of Until equal distribution of concentrations reached in all areas concentrations reached in all areas (EQUILIBRIUM)(EQUILIBRIUM)

– Due to the random movement of Due to the random movement of moleculesmolecules

Conceptual Diagram:Conceptual Diagram:

Can you think of Can you think of other examples?other examples?

DefinitionsDefinitions Solute:Solute:

– what gets dissolvedwhat gets dissolved Solvent:Solvent:

– What does the dissolving, more plentiful that What does the dissolving, more plentiful that solutesolute

Solution:Solution: – the mixture of solutes and solventthe mixture of solutes and solvent

Example: HExample: H22O and NaClO and NaClSolute: NaClSolute: NaClSolvent: HSolvent: H22OOSolution: HSolution: H22O and NaClO and NaCl

2. OSMOSIS:2. OSMOSIS:Definition:Definition: Diffusion (movement) of Diffusion (movement) of HH22O O through a through a

membranemembrane– from to high to low concentrationfrom to high to low concentration– until equilibriumuntil equilibrium

OSMOSIS:OSMOSIS:

3 Types of Solutions 3 Types of Solutions (outside of cell):(outside of cell):

1.1. HypertonicHypertonic

2.2. HypotonicHypotonic

3.3. IsotonicIsotonic

HypertonicHypertonic::

Hyper = MOREHyper = MORE– More More solutesolute, less , less

solvent (Hsolvent (H22O)O)outside of celloutside of cell

Water moves out Water moves out of cellof cell

““Hyper kids run out Hyper kids run out of school”of school”

Consequences:Consequences:

PLASMOLYSISPLASMOLYSIS (cell (cell shrinking)shrinking)– Examples:Examples:

Drinking out of ocean when you Drinking out of ocean when you are dying of thirst orare dying of thirst or

Placing a fresh water fish in salt Placing a fresh water fish in salt water… water…

Hypotonic:Hypotonic:

Hypo = LESSHypo = LESS– Less solute, Less solute,

more solventmore solventoutside of celloutside of cell

Water moves Water moves into cellinto cell

““HypHypO solution fills O solution fills cell with water”cell with water”

Consequences:Consequences: Hypotonic Hypotonic Cytolysis (cell bursting)Cytolysis (cell bursting)

– Examples: Examples: Place a salt water fish in fresh water Place a salt water fish in fresh water Red Blood Cells in pure waterRed Blood Cells in pure water

Turgor Pressure (Plants)Turgor Pressure (Plants) = Osmotic Pressure = Osmotic Pressure

As a result of osmosis, extra water As a result of osmosis, extra water molecules accumulate on one side of molecules accumulate on one side of membrane and cause pressure on the membrane and cause pressure on the membranemembrane

“ “Turgor”Turgor”

Example:Example:

water

Isotonic:Isotonic:

EQUALEQUAL– Equal amounts of Equal amounts of

solute/solvent solute/solvent concentrations on concentrations on both sides of both sides of membranemembrane

Water moves in and Water moves in and out of cell at an out of cell at an even rateeven rate

““Like a full Like a full restaurant – one restaurant – one family must leave family must leave for another to enter”for another to enter”

Which environment is best for Which environment is best for animal cells?animal cells?

(a) Isotonic

Water concentration inside the cells is equal to the water concentration in the fluid surrounding the cell. Therefore, there is no net movement of water either into or out of the cell.

(b) Hypertonic

Water concentration in the surrounding medium is lower than it is in the cell. Water moves out of the cells and the cells shrivel (crenate).

(c) Hypotonic

Water concentration outside the cell is greater than it is inside the cell. Water moves into the cell, which swell and sometimes burst – a process called lysis.

Which environment is best for Which environment is best for plant cells?plant cells?

III. FACILITATIVE III. FACILITATIVE DIFFUSION:DIFFUSION:

Protein Channels in the cell membrane accept Protein Channels in the cell membrane accept only specific particles, like a lock accepts a only specific particles, like a lock accepts a particular key.particular key.

III. FACILITATIVE III. FACILITATIVE DIFFUSION:DIFFUSION:

FACILITATIVE DIFFUSION:FACILITATIVE DIFFUSION: Many of these protein Many of these protein

channels are “two-way” channels are “two-way” and are called PORES.and are called PORES.

Like an open door Like an open door allows you to pass into allows you to pass into or out of a room.or out of a room.

Different solute Different solute particles fit different particles fit different porespores

This depends on This depends on – SizeSize– PolarityPolarity– Shape of moleculeShape of molecule

Ex. GlucoseEx. Glucose

DON’T FORGET, DON’T FORGET, – THESE WERE ALL THESE WERE ALL

PASSIVE TRANSPORT PASSIVE TRANSPORT – SO THE CELL DID NOT NEED TO SO THE CELL DID NOT NEED TO EXPEND ANY ENERGY TO MAKE IT EXPEND ANY ENERGY TO MAKE IT HAPPEN!!!!HAPPEN!!!!

Solvent (water) is always movingSolvent (water) is always movingEquilibrium (homeostasis) is the goalEquilibrium (homeostasis) is the goal