4. Difusion
O Small molecules like
oxygen or carbon
dioxide cross the cell
membrane. They
move towards the
side with less
concentration in
order to equal
concentrations.
5. Osmosis
O It is the difusion of water through the plasma
membrane. Water difuses from the least
concetrated side to the greater concentration side
until the concentrations become equal.
6. Active Transport
O Sometimes the cell
needs to take in
molecules that are in
a smaller
concentration in the
exterior. Therefore, in
order to introduce
them into the cell,
the cell needs to use
energy.
