Transport through the Cell Membrane

Review of the Types of Membranes: 1. Permeable 2. Impermeable 3. Semi-permeable

1. Permeable ALL types of molecules can get through, regardless of size or charge. ALL types of molecules can get through, regardless of size or charge. Permeable Pavement – ever been to Kane County Cougar’s Stadium?

2.Impermeable (non-permeable) NO molecules can get through

3. SEMI-PERMEABLE !!! : SOME MOLECULES CAN GET THROUGH SOME MOLECULES CAN GET THROUGH –Very small or –Non-charged

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

3 types: 1. Diffusion 2. Osmosis 3. Facilitated Diffusion

1. DIFFUSION: Definition: Transport of molecules (in general) –F–F–F–From an area of higher concentration to an area of lower concentration –U–U–U–Until equal distribution of concentrations reached in all areas (EQUILIBRIUM) –D–D–D–Due to the random movement of molecules

Conceptual Diagram: Can you think of other examples? Can you think of other examples?

Definitions Solute: –w–w–w–what gets dissolved Solvent: –W–W–W–What does the dissolving, more plentiful that solute Solution: –t–t–t–the mixture of solutes and solvent Example: H2O and NaCl Solute: NaCl Solvent: H2O Solution: H2O and NaCl

2. OSMOSIS: Definition: Diffusion (movement) of H 2 O through a membrane Diffusion (movement) of H 2 O through a membrane –from to high to low concentration –until equilibrium

OSMOSIS:

3 Types of Solutions (outside of cell): 1. Hypertonic 2. Hypotonic 3. Isotonic

Hypertonic: Hyper = MORE Hyper = MORE –More solute, less solvent (H 2 O) outside of cell Water moves out of cell Water moves out of cell “Hyper kids run out of school” “Hyper kids run out of school”

Consequences: PLASMOLYSIS (cell shrinking) –E–E–E–Examples: DDDDrinking out of ocean when you are dying of thirst or PPPPlacing a fresh water fish in salt water… 

Hypotonic: Hypo = LESS Hypo = LESS – Less solute, more solvent outside of cell Water moves into cell Water moves into cell “ Hyp O solution fills cell with water” “ Hyp O solution fills cell with water”

Consequences: Hypotonic Cytolysis (cell bursting) –E–E–E–Examples: PPPPlace a salt water fish in fresh water  RRRRed Blood Cells in pure water

Turgor Pressure (Plants) = Osmotic Pressure As a result of osmosis, extra water molecules accumulate on one side of membrane and cause pressure on the membrane As a result of osmosis, extra water molecules accumulate on one side of membrane and cause pressure on the membrane  “Turgor” Example: Example: water

Isotonic: EQUAL EQUAL –Equal amounts of solute/solvent concentrations on both sides of membrane Water moves in and out of cell at an even rate Water moves in and out of cell at an even rate “Like a full restaurant – one family must leave for another to enter” “Like a full restaurant – one family must leave for another to enter”

Which environment is best for animal cells?

Which environment is best for plant cells?

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

III. FACILITATIVE DIFFUSION:

FACILITATIVE DIFFUSION: Many of these protein channels are “two-way” and are called PORES. Many of these protein channels are “two-way” and are called PORES. Like an open door allows you to pass into or out of a room. Like an open door allows you to pass into or out of a room. Different solute particles fit different pores Different solute particles fit different pores This depends on This depends on –Size –Polarity –Shape of molecule Ex. Glucose Ex. Glucose

DON’T FORGET, DON’T FORGET, – THESE WERE ALL  PASSIVE TRANSPORT – SO THE CELL DID NOT NEED TO EXPEND ANY ENERGY TO MAKE IT HAPPEN!!!!  Solvent (water) is always moving  Equilibrium (homeostasis) is the goal