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Passive Transport

Passive Transport Where are membranes found? Cell Organelles

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Page 1: Passive Transport Where are membranes found? Cell Organelles

Passive Transport

Page 2: Passive Transport Where are membranes found? Cell Organelles

Where are membranes found?

• Cell• Organelles

Page 3: 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

Page 4: Passive Transport Where are membranes found? Cell Organelles

High Concentration Low Concentration

Concentration– amount of substance in

a given volume

Page 5: Passive Transport Where are membranes found? Cell Organelles

Passive

Passive Transport

•Movement of materials that DOES NOT require energy (ATP)

Page 6: Passive Transport Where are membranes found? Cell Organelles

Passive

Passive Transport

Diffusion

Page 7: Passive Transport Where are membranes found? Cell Organelles

Pas

sive

Tran

sport

High Concentration

Low Concentration

Page 8: Passive Transport Where are membranes found? Cell Organelles

Diffusion

• Move from HIGH to LOW concentration– “passive transport”– no energy needed

diffusion osmosis

movement of water

Page 9: Passive Transport Where are membranes found? Cell Organelles

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

Page 10: Passive Transport Where are membranes found? Cell Organelles

Diffusion• Continues until an equilibrium is

reached– Equilibrium – balanced; equally

distributed

Page 11: Passive Transport Where are membranes found? Cell Organelles

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

a

b

c

Page 12: Passive Transport Where are membranes found? Cell Organelles

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

Page 13: Passive Transport Where are membranes found? Cell Organelles

Factors Affecting Diffusion

•Temperature—the higher the temperature, the faster diffusion occurs

•Molecular Size—the bigger the molecule, the longer diffusion takes

Page 14: Passive Transport Where are membranes found? Cell Organelles

Osmosis

Passive

Passive Transport

Diffusion

Page 15: Passive Transport Where are membranes found? Cell Organelles

Osmosis

• Diffusion of water across a selectively permeable membrane.

• Occurs until concentration is balanced on both sides of the membrane.

Page 16: Passive Transport Where are membranes found? Cell Organelles
Page 17: Passive Transport Where are membranes found? Cell Organelles

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

Page 18: Passive Transport Where are membranes found? Cell Organelles

Hypertonic

• Medium has more solute than the cell

• More water leaves the cell than enters it

• Cell will shrink

Page 19: Passive Transport Where are membranes found? Cell Organelles

Hypotonic

• The medium has less solute than the cell

• More water enters the cell

• The cell will swell

Page 20: Passive Transport Where are membranes found? Cell Organelles

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

Page 21: Passive Transport Where are membranes found? Cell Organelles

What is happening here?

Page 22: Passive Transport Where are membranes found? Cell Organelles

Osmosis

Passive

Passive Transport

Diffusion

Facilitated Diffusion

Page 23: Passive Transport Where are membranes found? Cell Organelles

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

Page 24: Passive Transport Where are membranes found? Cell Organelles

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

Page 25: Passive Transport Where are membranes found? Cell Organelles

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

Page 26: Passive Transport Where are membranes found? Cell Organelles

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

Page 27: Passive Transport Where are membranes found? Cell Organelles

Active Transport

ATP ATP

Page 28: Passive Transport Where are membranes found? Cell Organelles

How about large molecules?

• Exocytosis– Through

vesicles & vacuoles

– “Exit Cell”

Page 29: Passive Transport Where are membranes found? Cell Organelles

Endocytosis

• Endocytosis– phagocytosis

= “cellular eating”

– pinocytosis = “cellular drinking

Page 30: Passive Transport Where are membranes found? Cell Organelles

Review

?

Page 31: Passive Transport Where are membranes found? Cell Organelles

Review

Page 32: Passive Transport Where are membranes found? Cell Organelles

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

Page 33: Passive Transport Where are membranes found? Cell Organelles

Transport summarysimplediffusion

facilitateddiffusion

activetransport

ATP

Page 34: Passive Transport Where are membranes found? Cell Organelles

Any Questions??