Cell Transport - Madison Public Schools
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Transcript Cell Transport - Madison Public Schools
Cell Transport
Facilitated Diffusion
Cells in their Environment
Active Transport
Passive Transport
1.
Diffusion- movement of molecules from an area
of high concentration to an area of low
2.
Osmosis- process by which water molecules
diffuse across a cell membrane from an area of
high concentration to an area of low
3.
Facilitated Diffusion- used for molecules that
cannot readily diffuse through cell membranes,
even when there is a concentration gradient…
Facilitated Diffusion
Facilitated Diffusion- carrier proteins in the
cell membrane assist molecules that cannot readily
diffuse across the cell membrane
Molecules cannot diffuse because:
May be not soluble in lipids
May be too large to pass through
Carrier proteins move molecules from a
higher to lower concentration, so no energy
is required… so it is PASSIVE TRANSPORT!
http://www.northland.cc.mn.us/biology/Biolo
gy1111/animations/active1.swf
Example of Facilitated Diffusion
Example= Glucose
Cells depend on glucose for energy
glucose molecules are too large to diffuse by simple
diffusion
When glucose levels in cell are lower than outside
the cell, carrier proteins transport glucose in
Cells in Hypotonic/ Hypertonic Environments
Cells exposed to an isotonic environment
usually have no trouble keeping the
movement of water across the membrane in
balance.
It is more difficult for cells in a
hypotonic/hypertonic environment
Contractile Vacuoles
Turgor Pressure
Plasmolysis
Cytolysis
Contractile Vacuoles
Unicellular freshwater organisms that live in
a hypotonic environment use contractile
vacuoles to rid excess water
Contractile Vacuoles- organelles that
collect excess water and then contract to
pump the water out of the cell
Pumping action requires cell to expend energy, it
is not a form of passive transport
Cytolysis
Red Blood Cells-
Lose their normal shape when exposed
to an environment that is not isotonic
Hypertonic environment = water leaves/ cells
shrink and shrivel
Hypotonic environment = water diffuses into cell/
cells swell and burst Cytolysis
Cytolysis – bursting of cells
Turgor Pressure
Most plant cells live in hypotonic environment- water moves into
plant cells by osmosis
Cells fill as they swell with water until cell membrane is pressed
against cell wall
Cell wall resists pressure exerted by water
Turgor Pressure- the pressure that water
molecules exert against cell wall
Plasmolysis
Plasmolysis- cells are in a hypertonic
environment and water leaves through
osmosis. Cells shrink away from the cell
walls (turgor pressure is lost)
This is the reason plants wilt if they don’t
receive enough water
Active Transport
Active Transport- movement of
materials from an area of lower
concentration to an area of higher
concentration. Requires a cell to expend
energy.
1.
Endocytosis
1.
2.
2.
3.
Pinocytosis
Phagocytosis
Exocytosis
Sodium-Potassium Pumps
Endocytosis
Endocytosis- process by which cells ingest
external fluid, macromolecules, and large
particles
1.
Pinocytosis- transport of solutes/ fluids
1.
2.
External materials are enclosed by a portion of the cells
membrane- folds into itself/ forms a pouch
Pouch pinches off and becomes a vesicle
http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/pinocyt.html
Phagocytosis- movement of large particles
1.
http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/phagocyt.html
Exocytosis
Exocytosis- process by which a substance is
released from the cell through a vesicle
(reverse of endocytosis)
Vesicles release their contents to the cell’s external environment
Ex: large molecules such as proteins, waste products, toxins
http://www.coolschool.ca/lor/BI12/unit4/U04L05/exocytosis.html
Sodium-Potassium Pumps
Sodium-Potassium pump – moves
substance (ions) from lower to higher
concentration/ require energy
Energy needed for active transport is supplied
directly or indirectly by ATP
http://highered.mcgraw-hill.com/olc/dl/120068/bio03.swf