Transport In & Out of Cell
Sections 3.3 – 3.4
• Purpose of Transport
– Laws of Nature (thermodynamics)
• Passive Transport
– Facilitated Diffusion
Types of Transport
Does not need energy
• Active Transport
– Ion pumps
– Endocytosis & Exocytosis
• What 3 things determine whether substances
cross the plasma membrane?
• What are some examples of what crosses and
what does not?
Terms to know
• A solution is a mixture of two or more
substances, evenly mixed
– The cytoplasm is a solution of many different
– Solutes = term for the substance dissolved in liquid
– Solvent = the substance that dissolves the solute
• Concentration = mass of solute in a given
volume of solution
Substances move by DIFFUSION
• Solutions try to achieve equilibrium
– Dynamic equilibrium
• Solutes will randomly move and try to spread
out as evenly as possible
– Entropy in the universe will tend to increase
• Substances will try to be equally concentrated
on the outside & inside of the cell membrane
Factors that Affect Diffusion
• Amounts of substances involved
-speeds up the rate of diffusion
Passive Transport [High] to [Low]
• Deals with movement of water
– From greater to lesser area of water
• Particles can’t move because membrane won’t allow it!
• When talking about cells…
– consider membrane only soluble to water (unless told otherwise)
– Concentration is relative to cytoplasm
Types of Solutions
the focus is on the particles (a lot or a little) in a particular
solution. But the action of water in response to this environment
is what we are concerned about.
If the cell is placed in …
• Hypotonic solution
– Solution that contains a smaller concentration of substance than
what is found in the cell (therefore “more water”)
Water will _____________ the cell
– Solution that contains a larger concentration of substance than
what is found in the cell (“less water”)
Water will _____________ the cell
– Concentration of substance outside the cell is the same inside
Water will _____________
• Pressure exerted on hypertonic side of a
selectively permeable membrane
– Cell walls prevent the cell from expanding
• Some organisms fight osmotic pressure by
using a contractile vacuole – pumps excess
water out of the cell
Effects of osmosis
• What are 3 major types of passive transport?
• What characterizes these as passive?
• Describe how the concentration of molecules
moves within this type of transport.
• What would happen to a red blood cell placed
in a hypertonic solution?
• ENERGY NEEDED!
– Mainly in the form of ATP
• Molecules go from lesser to
“against concentration gradient”
• Also when LARGE molecules
need to get through membrane
• May or may not need channel
proteins – called pumps
Explain this slide
Endocytosis and Exocytosis
• Endocytosis = process by which cells take in
large molecules from the outside
-eg.: pinocytosis – large amounts of liquid
phagocytosis – large amounts of solid
• Exocytosis = process by which cells get rid of
large molecules in the cell; leaves cell.
• Vesicle fuses with membrane to dispel
• Pinocytes are pockets on the cell
• Subtances are engulfed and a vacuole
forms around them
• This is when large
molecules are surrounded
and pulled into the cell
• Examples: amoeba, white
blood cells called
• This is the same method
used by white blood cells
to trap bacteria in our
• What are some examples of active transport?
• Describe the concentration gradient involved
in active transport
• How is active transport different from passive
• What’s happening in this picture?
• When is equilibrium reached?
• What is the difference between osmosis and
• What is the difference between active and
• A homeowner contracts a lawn company to
make the grass grow better. This process is
normally done by spraying a mixture of
fertilizer and water onto the lawn.
• What would happen if too much fertilizer and
too little water were sprayed onto the lawn?
• What happens to the cells of the grass?
• Was the fertilizer/water mix hypertonic or
hypotonic to the cells of the grass?