membrane transport1
TRANSCRIPT
The Cell as the The Cell as the Fundamental Unit of Fundamental Unit of
Life: Life: Membrane Membrane Transport ProcessesTransport Processes
Selectively permeable- allows certain substances to pass through
By 2 ways: active or passive transport
Passive- downhill
Active- uphill (needs energy)
Plasma Membrane Function:Plasma Membrane Function:
Passive: downhill reaction• Simple diffusion• Osmosis• Facilitated diffusion• Filtration
Active: uphill reaction, needs ATP• Exocytosis• Endocytosis
- Pinocytosis- Phagosytosis
No Barrier: Substances “spread out”
High concentration to low concentration
e.g.: Red dye placed in glass of water
Passive Diffusion
Substances diffuse
High concentration to low concentration
Pores in membrane must be large
“Down the concentration gradient”
Dynamic equilibrium, equal rates in both directions
Passive Diffusion
Biological membrane:
Facilitated
Diffusion
Carrier proteins:
• Bind specific molecule & change shape
• Pass molecule through middle of protein
Passive Diffusion: OsmosisOsmosis- diffusion of a water through a semi-permeable membrane
•Moves down concentration gradient
e.g. Two sugar solutions of different concentrations separated by porous membrane which lets water through but not sugar
What will happen?
Passive Diffusion: Terms & Osmosis
More concentrated to less concentrated Until concentration same on both sides: isotonic
Passive Diffusion: Osmosis &Terms
Concentration of solute less: solution is hypotonic.
Concentration of solute greater: solution is hypertonic.
Passive Diffusion: Osmosis: Outcomes to Living Cells (Animal)
Animal cells No cell walls
Isotonic environment: Influx of water equals the efflux of water No change in cell shape
Passive Diffusion: Osmosis: Outcomes to Living Cells (Animal)
Hypotonic solution: Water enters cell Bursts, or lyses
Hypertonic solution: Water leaves cell Shriveled, or crenate
Passive Transport and Facilitated Diffusion
Passive transport & facilitated diffusion do NOT require
ATP
Active Transport
DOES require the input of
ATP
Transport proteins AGAINST concentration
gradient
outside cell
inside cell
ATPATP
Role of ATP in Energy Role of ATP in Energy MetabolismMetabolism
ATP ATP ADP + P ADP + Pii + Energy + Energy
EndocytosisEndocytosis
ExocytosisExocytosis
SecretionSecretion
ExocytosisExocytosis
nuclei
mucus
Membrane Permeability
Cell membrane:
selectively permeable
4 factors that determine permeability lipid solubility
molecular size
polarity
charge
1
2
3
4
Lipid solubility Most important factor
Hydrophobic molecules Passively diffuse Hydrocarbons, carbon dioxide, & oxygen
Molecular Size and Polarity
Larger molecules, less permeable Lower kinetic energy Small pore sizes in the membrane
Polar molecules hydrophilic, less permeable Very small, polar uncharged (water) molecules can diffuse
-+
Molecular Size
Polarity
Charge
Charged molecules hydrophilic, less permeable Surrounded by coat of water (hydration shell), increases the size