Transcript Membrane Structure and Function Ch. 7

Membrane Structure and
Function Ch. 7
Membrane Protein Functions
Types of Transport
•
•
•
•
•
Diffusion
Osmosis
Facilitated Diffusion
Active Transport
Endocytosis/exocytosis
• Which are passive transport??
Types of Transport
•
•
•
•
•
Diffusion
Osmosis
Facilitated Diffusion
Active Transport
Endocytosis/exocytosis
Passive = does not
require energy
• Which are passive transport??
Diffusion
• Movement of molecules from high
concentration to low concentration
• “down a concentration gradient”
• Brownian movement = natural movement
of molecules
• Oxygen, carbon dioxide, alcohol and urea
move by simple diffusion in cells
Examples of diffusion
• Perfume opened in a room
• Drop of food coloring in glass of water
• Lung cell: carbon dioxide diffuses from
lungs to the air, oxygen diffuses into cells
Rate of diffusion
• Temperature: Increased temperature,
increases diffusion rate
• Size of molecule: smaller molecules
diffuse faster
• Concentration gradient: bigger difference
in concentration, faster diffusion
Osmosis
• The movement of water across a semipermeable membrane in response to a
concentration gradient
• Osmolality = solute concentration
Hyper = more
Hypo = less
Iso = same
• Tonicity = movement of water in response
to solute concentration
crenation
Osmometer
• Sugar concentration in tube
• Sugar cannot pass out of tube, so water
moves into tube
• Pushes fluid level up
• Pull of water into the tube = “osmotic
pressure”
• Water moves from hypo  hyperosmotic
solution
Osmoregulation
• Control of water balance
• Paramecium uses contractile vacuole
• We use our kidneys
• Our kidneys filter our blood and maintain
salt and water balance
Transport by Carriers
Facilitated Diffusion
Active Transport
Uses specific membrane proteins
Uses specific membrane proteins
Substances transported from
high to low concentration
Substances transported from low
To high concentration
Passive
Requires energy input (ATP)
Sugars, amino acids
Ions, sugars, amino acids
Both use lock and key mechanism to move molecules using
membrane proteins that span the membrane
Facilitated Diffusion
Active Transport
Summary
Endocytosis = using the cell membrane
to move materials into cell
Phagocytosis: Amoeba engulfing a bacterium
Receptor Mediated Transport
Exocytosis = using cell membrane to
move materials out of cell