Transcript Transporting Materials Across the Cell Membrane

Transporting Materials
Across the Cell
Membrane
Osmosis, Diffusion, and
Active Transport
Demonstration
• Sketch a diagram of the beaker and
water
• Get a colored pencil and draw what
happens the instant the dye hits the
water
Diffusion
• Is the movement of materials from
a region of high concentration to a
region of low concentration
• Equilibrium is reached when the
concentrations are equal
• You experience this when burnt
toast from the kitchen wafts down
to your room
Demonstration, cont’d
• Observe the beaker with dye now
• How is it different from when the dye
first went in?
Osmosis
• Is the movement of water from a
region of high concentration to a
region of low concentration until
equilibrium is reached
• You experience osmosis when
lettuce left out on the counter wilts
– the water is moving from high
conc (in lettuce) to low conc (in
air)
• Both diffusion and osmosis are
passive – do not require ATP
(energy)
Cell Membrane
• Is composed of a double layer of lipid
molecules in which proteins are
embedded
• Cell membrane regulates passage of
substances into and out of the cell
and is said to be a selectively
permeable membrane, meaning not
all substances will pass through it
Cell Membrane
Cell Membrane
• Many substances can pass freely
through the cell membrane, such as
water, CO2 and O2
• Other substances are too large to fit
through the pores and need help.
Carrier proteins aid in moving large
molecules from the outside to the
inside of the cell. This is called…
Facilitated Diffusion
Demonstration
Note that
molecules are
moving from a
region of high
conc to a
region of low
conc.
Therefore, this
is still diffusion.
http://bio.winona.msus.edu/berg/ANIMTNS/FacDiff.htm
How Facilitated Diffusion Works
• http://highered.mcgrawhill.com/sites/0072495855/student_
view0/chapter2/animation__how_fac
ilitated_diffusion_works.html
Active Transport
• Sometimes substances that need to
get into cells are in higher conc in
the cells – diffusion won’t work
• Some materials are transported
against a conc gradient (from low to
high). In these cases energy must
be used. Energy in cells is ATP.
Active Transport
• Active transport is the movement of
a substance from a region of low
conc to a region of high conc with
the expenditure of energy
• Without active transport, your
kidneys would not reabsorb precious
water, your muscles would not
contract, and your nerves could not
carry impulses.
Active Transport
Carrier proteins
require energy in
the form of ATP to
move the
substances across
the membrane
Endocytosis
• Very large molecules must
sometimes get into the cell but will
not fit through the pores nor the
carrier proteins
• Endocytosis is a process where a cell
engulfs large particles by extending
its cytoplasm around the particle,
trapping the particle in a vacuole.
Endocytosis
Two types:
1) Phagocytosis is
when the cell
engulfs solid
particles
2) Pinocytosis is
when the cell
engulfs liquid
droplets.
Exocytosis
• Exocytosis is the process by which
large molecules are transported out
of the cell, such as waste materials.
• The Golgi complex packages the
departing substances into vesicles,
which fuse with the cell membrane
and rupture, dumping their contents
to the outside.
Exocytosis
Endocytosis/Exocytosis
Animation
• http://highered.mcgrawhill.com/olc/dl/120068/bio02.swf
Summary
Passive
Active
(no ATP required)
(ATP required)
Diffusion
Active Transport
Osmosis
Endocytosis
Facilitated Diffusion
Exocytosis