Cell Transport Vocabulary
Solution – Solute - Solvent
• Solute – The substance that dissolves to form
a solution
• Solvent – The substance in which a solute
dissolves
• Solution – A mixture of one or more solutes
dissolved in a solvent
Semi-permeable membrane
• This membrane lets certain molecules pass
through and prevents others from crossing
Passive transport
• the movement of substances across the plasma
membrane from areas of high concentration to
low concentration; does not require cellular
energy.
• EX:
– Diffusion
– Facilitated diffusion
– Osmosis
Diffusion
• the movement of particles from areas of
higher concentration to areas of lower
concentration.
Facilitated Diffusion
• A process
where a
substance
passes through
a membrane
with a aid of an
protein carrier,
no energy
required
Protein Carrier
Osmosis
• diffusion of water through a semi-permeable
membrane
• Water will move in the direction where there
is a high concentration of solute (and hence a
lower concentration of water)
Osmotic Pressure
• The pressure exerted by the flow of water
through a semipermeable membrane
separating two solutions with different
concentrations of solute.
• EX:
– Hypotonic solution
– Hypertonic solution
– Isotonic solution
Osmotic Solutions
• Hypotonic solution (“POW”)
– If concentrations of
dissolved solutes are less
outside the cell than inside,
the concentration of water
outside is correspondingly
greater.
• When a cell is exposed to
such hypotonic conditions,
there is net water movement
into the cell causing cell to
burst.
Osmotic Solutions
• Hypertonic solution –
If concentrations of
dissolved solutes are
greater outside the cell,
the concentration of
water outside is
correspondingly lower.
• As a result, water inside
the cell will flow
outwards to attain
equilibrium, causing the
cell to shrink.
Osmotic Solutions
• Isotonic solution - When cells are in isotonic
solution, movement of water out of the cell is
exactly balanced by movement of water into the
cell.
Active transport
• the movement of substances across the plasma
membrane from areas of Low concentration to
high concentration; requires cellular energy.
• The movement of macromolecules(large
molecules such as proteins or polysaccharides
into or out of the cell is called bulk transport.
• 2 types of bulk transport
– Exocytosis
– Endocytosis
Active Transport
• Endocytosis - the
process by which
materials move into the
cell.
• Phagocytosis - “cellular
eating,” the cell’s
plasma membrane
surrounds a
macromolecule
• Pinocytosis - “cellular
drinking,” the cell
engulfs drops of fluid by
pinching in and forming
vesicles
Active Transport
• Exocytosis - materials are
exported out of the cell via
secretory vesicles
– Golgi complex packages
macromolecules into
transport vesicles that
travel to and fuse with the
plasma membrane.
Concentration Gradient
• a difference between concentrations in a space
Equilibrium
• a state of equilibrium is reached when the
concentrations of solutes and water is the
same inside and outside the cell.
Dialysis
• the process of solute movement across a
semi-permeable membrane.