Plasma membrane/cell membrane
How does it control what goes into and out
of the cell????
Permeable: Can pass through
Selectively Allows only certain
permeable: molecules to pass
through
BUT
Not all molecules get in the same way!
Selective Permeability
O2, CO2,
and other small, nonpolar
molecules; some water
molecules
glucose and other large, polar,
water-soluable molecules; ions,
water molecules
Nonpolar= equal charge throughout molecule
Polar= uneven charge in molecule
Types of Transport
Passive
(no NRG)
Active
(requires NRG)
NRG= ENERGY
• Whether passive or active transport is
needed depends on the
CONCENTRATION GRADIENT
• The concentration gradient is the
difference in the concentration of a
substance in two different spaces
• Concentration - the amount of a
particular substance in a contained
area compared with the amount of the
same substance in another area
• Translation: Amount of something in a
space (water, salt, sugar, iron,)
Transport within the cell
Passive transport: No energy needed
Follows concentration gradient (high to low)
Active transport: Energy needed
Against concentration gradient: Low to high
(Adenosine triphosphate)
Passive Transport
Passive
Diffusion
Facilitated
Diffusion
Osmosis
High Concentration
Low Concentration
High
Concentration
Low
Concentration
Passive Transport
Diffusion
“out”
Movement of SUBSTANCE from area of high
concentration to area of low concentration
H L
Equilibrium reached when molecules are evenly distributed
Passive transport
Factors Affecting
Diffusion Rate
• Steepness of concentration gradient
– Steeper gradient, faster diffusion
• Molecular size
– Smaller molecules, faster diffusion
• Temperature
– Higher temperature, faster diffusion
• Charge
– Charged molecules cannot diffuse (NaCl Na+ Cl-)
Facilitated
Diffusion
Faster than diffusion
Glucose
molecules
High
Concentration
Cell
Membrane
Low
Concentration
Protein
channel
Protein channel recognizes molecule and allows entry
No NRG required, following concentration gradient
Osmosis
Diffusion of WATER across a membrane
Which has more water?
100 ml
Distilled
H20
100 ml
10% Salt
solution
Osmosis
Water will move into or out of cell following the
concentration gradient of water
Where is there more water???
Osmosis in ANIMAL CELLS
• In Pure water
• In STRONG Sugar solution
WEAK sugar/salt
solution INSIDE
animal cell
Cell swells & ... LYSE (BURST)
WEAK sugar/salt
solution INSIDE
animal cell
Cell shrinks
Osmosis in PLANT CELLS
• In Pure water
WEAK sugar/salt
solution INSIDE
potato cell
Cell swells : TURGID
• In STRONG Sugar solution
WEAK sugar/salt
solution INSIDE
potato cell
Cell shrinks : PLASMOLYSED
Plasmolysis
Plasmolysis video site
http://www.uic.edu/classes/bios/bios100/lectf03am/plasmolysis.jpg
Cell Size
How does the size of a cell affect the
rate of exchange of materials in and
out of the cell?
The bigger the surface area of
the cell membrane, the more
materials can diffuse in and
out of the cell.
Active Transport
Active
Pumps
Membrane
Movements
Endocytosis
Exyocytosis
Against concentration
gradient
Uses NRG (ATP)
High Concentration
Low Concentration
Active Transport
LC
HC
Transport Proteins
• Span the lipid bilayer
• Interior is able to open to both sides
• Change shape when they interact with
solute
• Move water-soluble substances
across a membrane
Pumps
Membrane
Movements
Exocytosis
plasma membrane
Endocytosis and
Exocytosis
cytoplasm
Endocytosis
cytoplasm
Exocytosis
Pinocytosis (cell drinking)
Process where cell membrane “pinches in”
drawing molecules into the cell forming a
pinocytic vesicle
Phagocytosis (cell eating)
Process where pseudopods of a
cell flow around matter and engulf it
forming a food vacuole
Phagocytosis (Movie)
What about single celled organisms that live in freshwater
(amoeba/paramecium)? Why don’t they burst?
Active Transport: going against the gradient
Active Transport
Passive Transport:
• Mvmt of materials using • Mvmt of materials
energy.
Without use of energy.
• Against Concentration
gradient
• LCHC
• With Concentration
Gradient
• HCLC
• Examples:
– Endocytosis
• Phagocytosis
• Pinocytosis
– Exocytosis
• Examples:
– Diffusion
– Osmosis
– Facilitated Diffusion
Video 4
Active Transport
• video segment.
Animations
Dialysis Bag Experiment
• http://ccollege.hccs.cc.tx.us/instru/Biology/AllStudy
Pages/Diffusion_Osmosis/Baggif.swf
Elodea Cell
• http://ccollege.hccs.cc.tx.us/instru/Biology/AllStudy
Pages/Diffusion_Osmosis/Elodeagif.swf
Osmosis
• http://ull.chemistry.uakron.edu/genobc/animations/o
smosis.mov