Cellular Transport
Passive Transport
• Movement of molecules across the membrane
• No energy needed
• High to low concentration
• Ex: diffusion, osmosis, facilitated diffusion
Diffusion
• Robert Brown – Scottish scientist in 1827
discovered Brownian motion.
▫ Random movement of molecules
• Movement from high to low concentration.
Diffusion
• Affected by:
▫ Concentration – the higher the concentration, the
faster it diffuses; the lower the concentration, the
slower it diffuses.
▫ Size and type of molecule
▫ Temperature – the warmer the temperature, the
faster it diffuses; the colder the temperature, the
slower it diffuses.
Dynamic Equilibrium
• Reached when movement in the cell is equal to
the cell balance
Osmosis
• Movement of water molecules through a
selectively permeable membrane
• Types of diffusion
▫ Isotonic solution – movement same in and out
▫ Hypotonic solution – gain turgor pressure, swells
and may burst
▫ Hypertonic solution – loss of turgor pressure,
water leaves cell, shrinkage occurs
 Plasmolysis (cell wilts)
Diffusion Process
OUT
IN
food
carbohydrates
sugars, proteins
amino acids
lipids
salts, O2, H2O
IN
OUT
waste
ammonia
salts
CO2
H 2O
products
Facilitated Diffusion
• Use Transport Proteins that
span the cell membrane
• Transport proteins
▫ Channel proteins: provides
tube-like opening in the
plasma membrane through
which particles can diffuse
▫ Carrier Protein: changes
shape
“The Bouncer”
Osmosis
►http://www.ias.ac.in/initiat/sci_ed/resources/ch
emistry/osmosis3.gif
Osmosis Related to Red Blood Cells
►http://www.ndpteachers.org/perit/osmosis2.gif
Active Transport
• Requires additional
energy and transport
proteins
• Low concentration to
high concentration
low
ATP
high
Extra Terms
• Endocytosis – large molecules enter cell
• Exocytosis – large molecules exit the cell (waste)
Exocytosis 
Video Sample
Transport Video