Transcript high concentration to

Movement Through the
Membrane
•The Cell boarder is very important
•It regulates what enters and leaves the
cell.
•It provides protection and support.
Functions of the cell membrane.
•1. Provides boundary
for cell
•2. Selectively
permeable- only allows
certain things to pass
through- “Picky”
Ex. Window screen
•3. Maintains
homeostasis: balance
within the cells
The Cell Membrane
•
•
•
Membrane is a lipid
bilayer
Phospholipids: fatty
areas that attract
(hydrophilic) and
repel (hydrophobic)
water
Embedded proteins:
“club bouncers”
– Decides what goes in &
out
– Markers for recognition
The lipid bilayer has proteins
embedded in it.
Cell
Membrane
Proteins
Protein
channel
Carbohydrate
chains
Lipid bilayer
• Passive transport: Diffusion - the
movement of a substance from an area
of high concentration to an area of
lower concentration (a concentration
gradient).
PASSIVE TRANSPORT = NO energy
1. Diffusion: movement
of particles from high to
low concentration
Water
Molecule
Sugar
Molecule
High
concentration
Ex. Perfume & Body odor
2. Osmosis: movement
of water from high to low
concentration.
•-Turgor Pressure- cell
explode
Low concentration
Both occur through bilayer and Do NOT require
cell energy. Movement occurs until equilibrium
is reached.
• Osmotic pressure always moves water
toward the hypertonic side (the side
containing the least amount of water) of a
membrane.
Three Strengths of Solutions.
• Isotonic
• Hypotonic
• Hypertonic
• ISOTONIC:
• particles outside =
particles inside
• ISO- means “equal
to”
• Movement into cell=
movement out of cell
•HYPOTONIC:
concentration of dissolved
substances is lower outside
cell than inside cell
•HYPO = “below strength”
•Water will move INTO cell
causing it to swell - water
always moves to areas of
greater concentration (more
“stuff”)
•Cells could rupture if the
cell takes in too much water
•This increases pressure
inside of cell = TURGOR
PRESSURE
Hypo –Hippo 
•HYPERTONIC:
concentration of dissolved
substances is higher
outside the cell
•HYPER = “above
strength”
•Water rushes OUT of cell
causing it to shrivel (water
rushes to where there is
more substances)
•Can result in
PLASMOLYSIS in plants
which causes wilting
Red Blood Cells
Remember!
• Osmosis & Diffusion
are passive transport!!
Meaning the cell does
not have to use any
energy to perform
these!
Active Transport.
• transport against
concentration
gradient; goes from
low to high
concentration
• Go through protein
channel
• This requires energy
to move them into
cell; ex: Na-K pump
Molecule to
be carried
Low
Concentration
High
Concentration
Molecule
being carried
Energy
•Types of active
transport:
http://www.linkpublishing.com/videotransport.htm#LINKS_
•ENDOCYTOSIS: cells
take in large clumps of
substances
•Phagocytosis: “cell
eating” take in food
•Pinocytosis: “cell
drinking” take in water
•EXOCYTOSIS: cells
move substances out
(exit) ex: wastes
Cell Eating
Cell Drinking
High
Concentration
Glucose
molecules
•FACILITATED
TRANSPORT:
•type of diffusion as
movement is from high
to low concentration
•this type goes
through a protein
channel rather than
bilayer.
Low
Concentration
Protein
channel
•Proteins –picky
“bouncers”
Summary
• Diffusion & Osmosis
– high to low concentration
– goes in between phospholipid spaces
– no energy= Passive transport
• Active transport– low to high concentration
– requires energy
– goes through protein
• Facilitated Transport– high to low concentration
– no energy
– goes through protein
`
Summary
• Ex. Party
1. Air coming into a window screen
2. Someone opens the door & you walk
through (door represents protein)
3. someone goes through the back door
that is already open
coming in=Endocytosis
going out= Exocytosis
• Summary