Plasma Membrane &
Cellular Transport
http://www.i-sup2008.org/images/venue_transport.jpg
Cell Transport
A cell has to move food and wastes into and out
of the cell. Materials must move through the
plasma membrane which maintains
homeostasis in the cell.
food
food
waste
waste
waste
waste
food
food
Cell Transport
The Plasma Membrane surrounds the cell. How
does it work?
Plasma Membrane
Boundary between the cell and its environment
1. Allows nutrients into the cell
2. Removes wastes and excess materials
3. Maintains homeostasis: a stable internal
environment
Plasma Membrane
How does it work?
1. Semi-permeable: only allows some molecules in the cell, keeps others out
2.
Fluid Mosaic Model: membrane is flexible, made of many pieces working
together
http://www.youtube.com/watch?v=Qqsf_UJcfBc
Plasma Membrane
3. Phospholipid Bilayer: membrane is 2 layers,
made of phosphates and fats (lipids) with
proteins mixed in
Plasma Membrane Parts
Phosphate heads – hydrophilic (like water), outside
and inside membrane
Fatty Acid Tails – hydrophobic (fear water), inside
membrane, like OREO cream
Cholesterol – prevents fats from sticking together,
stabilize membrane
Transport proteins – move molecules into and out
of cell
Identification proteins – outside cell, “nametag”
Support proteins – inside cell for framework,
“skeleton”
Passive Transport
NO ENERGY required, moves molecules from
high concentration to low concentration
1. Osmosis
movement of water across a membrane
http://schools.moe.edu.sg/chijsjc/Biology/Diffusion&osmosis/osmosis.gif
Passive Transport – no energy required
2. Diffusion
molecules move from an area of high
concentration to low concentration
http://iweb.tntech.edu/mcaprio/diffusion-animated.gif
Passive Transport – no energy required
3. Facilitated Diffusion
movement of molecules from high
concentration to low concentration with help of
membrane transport proteins
Low concentration
High concentration
http://www.biology.arizona.edu/CELL_BIO/problem_sets/membranes/graphics/CHANNEL.GIF
Active Transport
Requires energy
Moves molecules against concentration gradient
Moves from area of low concentration to high
concentration
Examples:
gated channels, sodium/potassium pumps,
endocytosis, exocytosis
Active Transport
Endocytosis and Exocytosis
http://media-2.web.britannica.com/eb-media/38/8038-004-A29C9C02.jpg
Active Transport
Example: Paramecium uses contractile vacuole
to regulate water content
http://www.cartage.org.lb/en/themes/sciences/BotanicalSciences/MajorDivisions/KingdomPr
otista/Protists/paramecium.gif
Solutions
Isotonic solution – equal concentrations of
solute (salt) inside and outside cell
http://www.biologycorner.com/resources/isotonic.gif
Solutions
Hypotonic solution – less solute in solution, more
solute in cell, WATER FOLLOWS SALT, cells swell
http://www.biologycorner.com/resources/hypotonic.gif
Solutions
Hypertonic solution – more solute in solution,
less solute in cell, WATER FOLLOWS SALT, cells
shrink
http://www.biologycorner.com/resources/hypertonic.gif
Osmosis in blood cells
http://aryatiabdul.files.wordpress.com/2008/07/osmosis2.gif
Solutions – how transport affects
animals and plants
http://kentsimmons.uwinnipeg.ca/cm1504/Image130.gif
Transport in Plants
Healthy
plant cells
are crisp
due to
TURGOR
PRESSURE
Wilted plant
cells are
flaccid due to
lack of water