passive transport where are membranes found? cell organelles
TRANSCRIPT
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 Concentration Low 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
Pas
sive
Tran
sport
High Concentration
Low Concentration
Diffusion
• Move from HIGH to LOW concentration– “passive transport”– no energy needed
diffusion osmosis
movement of water
Diffusion across cell membrane
• Cell membrane is the boundary between inside & outside…– separates cell from its environment
IN: foodcarbohydratessugars, proteinsamino acidslipidssalts, O2, H2O
OUT: wasteammoniasaltsCO2
H2O 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?
a
b
c
What causes diffusion?
• Movement of molecules– As they move they bump into each
other
• Collisions cause molecules to move away from each other
– http://www.stolaf.edu/people/giannini/flashanimat/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 H2Osugar
NH3
What molecules can NOT get through directly?
polar molecules
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
sugaraaH2O
saltNH3
Facilitated Diffusion
• Diffusion through protein channels– channels move specific molecules across
cell membrane– no energy needed
“The Bouncer”“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 ATP
How about large molecules?
• Exocytosis– Through
vesicles & vacuoles
– “Exit Cell”
Endocytosis
• Endocytosis– phagocytosis
= “cellular eating”
– pinocytosis = “cellular drinking
Review
?
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 summarysimplediffusion
facilitateddiffusion
activetransport
ATP
Any Questions??