Passive Transport

Where are membranes found? Cell Organelles

Cell Membrane Allows certain things to enter and leave Phosphate head Lipid tail Two layers a.k.a. semipermeable phospholipid bilayer

High ConcentrationLow Concentration Concentration – amount of substance in a given volume

Passive Passive Transport Movement of materials that DOES NOT require energy (ATP)

Passive Passive Transport Diffusion

Passive Transport High Concentration Low Concentration

Diffusion Move from HIGH to LOW concentration –“passive transport” –no energy needed diffusionosmosis movement of water

Diffusion across cell membrane Cell membrane is the boundary between inside & outside… –separates cell from its environment IN: food carbohydrates sugars, proteins amino acids lipids salts, O 2, H 2 O OUT: waste ammonia salts CO 2 H2OH2O products IN OUT

Diffusion Continues until an equilibrium is reached –Equilibrium – balanced; equally distributed

What will happen when dye is added to a beaker of water? abc

What causes diffusion? Movement of molecules –As they move they bump into each other Collisions cause molecules to move away from each other – nimat/transport/diffusion.swfhttp:// nimat/transport/diffusion.swf

Factors Affecting Diffusion Temperature —the higher the temperature, the faster diffusion occurs Molecular Size —the bigger the molecule, the longer diffusion takes

Osmosis Passive Passive Transport Diffusion

Osmosis Diffusion of water across a selectively permeable membrane. Occurs until concentration is balanced on both sides of the membrane.

Osmosis is diffusion of water Direction of osmosis is determined by comparing total solute concentrations – Hypertonic - more solute, less water – Hypotonic - less solute, more water – Isotonic - equal solute, equal water

Hypertonic Medium has more solute than the cell More water leaves the cell than enters it Cell will shrink

Hypotonic The medium has less solute than the cell More water enters the cell The cell will swell

Isotonic Medium is exactly the same solute concentration as the cell Amount of water moving in equals water going out The cell will stay the same size

What is happening here?

Osmosis Passive Passive Transport Diffusion Facilitated Diffusion

Isnt the membrane “semi-permeable”? What molecules can get through directly? –fats & other lipids inside cell outside cell lipid salt aa H2OH2O sugar NH 3  What molecules can NOT get through directly?  polar molecules H2OH2O  ions  salts, ammonia  large molecules  starches, proteins

Channels through cell membrane Membrane becomes semi-permeable with protein channels –specific channels allow specific material across cell membrane inside cell outside cell sugaraa H2OH2O salt NH 3

Facilitated Diffusion Diffusion through protein channels –channels move specific molecules across cell membrane –no energy needed “The Bouncer” open channel = fast transport facilitated = with help high low

Active Transport Cells may need to move molecules against concentration gradient –shape change transports solute from one side of membrane to other –protein “pump” –“costs” energy = ATP ATP low high

Active Transport ATP

How about large molecules? Exocytosis –Through vesicles & vacuoles –“Exit Cell”

Endocytosis –phagocytosis = “cellular eating” –pinocytosis = “cellular drinking

Review ?

Getting through cell membrane Passive Transport –Simple diffusion diffusion of nonpolar, hydrophobic molecules –lipids –high  low concentration gradient –Facilitated diffusion diffusion of polar, hydrophilic molecules through a protein channel –high  low concentration gradient Active transport –diffusion against concentration gradient low  high –uses a protein pump –requires ATP ATP

Transport summary simple diffusion facilitated diffusion active transport ATP

Any Questions??