Lesson 2: Obtaining and
removing materials
Recap
1.
A cell membrane is more flexible than a brick wall. Why might cells
benefit from having a flexible cell membrane?
2.
Which type of transport is shown in the image below? Why?
3.
Which type of transport is shown in the image below? Why?
4.
Why is it imporatnt for a cell membrane to be selectively
permeable?
Diffusion continued.
The cells in
our lungs re
in contact
with the air
that we
breathe.
The air outside the
cell has a higher
concentration of
oxygen so oxygen
moves into the cell
through diffusion.
The diffusion of oxygen into
the cell does not require the
cell to use any of its energy
(diffusion is a form of passive
transport).
Osmosis
Osmosis is the
diffusion of water
olecules across a
selectively
permeable
membrane.
Many cellular
processes
depedn on
osmosis to bring
them the water
they need
Osmosis is a form of
passive trsnport
becvaue it requires
no energy fom the
cell
Facilitated diffusion
Oxygen, carbon dioxide and
water cn diffuse easily across
the cell membrane. Some
molecules cannot easily croos
the membrane e.g sugar
Facilitated
diffusion uses
no cell energry
and is a form
of passive
taransport
Proteins in the
ceel
memebrane
form a path for
sugars diffuse.
Active Transport
During diffusion,
molecules move from a
higher concentration to
a lower one
Cells need the
concentraion of
molecules inside
the cell to be
higherthanthe
concentarion
outside of the cell
To maintain this
difference in
concentration, cells
must use ctive
transport
Active transport
is the movement
of materials
across a cell
membrane using
cellular energy
Protiens in the cell
membrane play
an imporatnt role
in active trasnport
Trasnport protiens pick up
molecules passing by the cell
and carry them across the
memebrane. Calcium,
potassium and sodium are
some substances that are
carried
Moving Large Particles
Some particles
are toolarge to
cross the cell
membrane
Endocytosis is a
process where
the cell
membrane
changes shape
and covers these
particles. The
food particle is
then carried into
the cell
Exocytosis
allows large
particles to
leave the cell.
The vacuole
arounfd the
particle fuses
with the cell
membrane
and frocres
the molecule
out