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SECTION 2.3
MOVING CELLULAR MATERIAL
PASSIVE TRANSPORT
 Passive transport is the
of substances through a cell
membrane
using the cell’s energy.
 Small molecules, such as oxygen and carbon dioxide, pass through
via passive transport.
 Passive transport
on the amount of substance on each side
of a membrane.
DIFFUSION
 Concentration- The number of
of a substance in a specific volume.
 Diffusion occurs when there is a difference in concentration between
areas of a substance.
 Equilibrium- The point at which the
of a substance is
between the two areas.
 Diffusion occurs until equilibrium is reached.
 Diffusion is the movement of substances from an area of
concentration to an area of
concentration.
DIFFUSION IN CELLS
 Diffusion is one way materials move into and out of cells.
 Oxygen and carbon dioxide
by diffusion.
 Diffusion can occur from one cell to the next.
 Diffusion continues until the concentration of a substance is the
on both sides of the membrane. The substance is then in equilibrium.
OSMOSIS—THE DIFFUSION OF WATER
 Osmosis is the diffusion of
molecules through a membrane.
 The Semi permeable cell membranes allow water to pass through until
occurs.
FACILITATED DIFFUSION

diffusion occurs when molecules pass through a
cell membrane using special
called transport
proteins.
 Transport Proteins
o Carrier proteins carry
molecules through the cell
membrane. Ex. sugar
o
proteins form pores through the cell
membrane. Ex. Potassium K, Sodium Na
SOME TRANSPORT REQUIRES ENERGY
 For cells to carry out the
functions often materials must move from
areas of lower concentration this requires the energy. Ex: plant root cells
 Active transport- The process of using
to move
materials through the membrane.
ENDOCYTOSIS
 Endocytosis- When cells need to move
molecules into the cell.
 Cell membrane forms around molecule
 White blood cells can take in bacteria and digest them to help us fight disease.
EXOCYTOSIS
 Exocytosis- When cells need to
large particles out of the cell.
CELL SIZE AFFECTS TRANSPORT
 Everything that the cell needs or has to get rid of must go through the cell
membrane.
 The surface area of the cell is the cell membrane.
 Amount of cell membrane = amount of cell surface area
 The volume is the amount of space inside the cell.
 As a cell gets larger, its volume increases faster than its surface area.
 The area of the cell membrane must be large compared to its volume so that
substances can move into and out of the cell.
 As the cell gets bigger, there comes a point when the surface area is not large
enough to allow resources to travel to all the parts of the cell.
 Remember the cell stops growing (and may divide).