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
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