http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html
http://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf
Membranes can impede diffusion
semi-/selectively permeable
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.htm
Membrane proteins aid diffusion of specific molecules
act as carriers, form channels
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html
EX: Insulin receptor
triggers the movement of
glucose transporters to
the CM
these transporter proteins
facilitate the diffusion of
glucose across the
membrane
When the
molecule
diffusing is
water, it’s called
osmosis
Less solute concentration
Therefore more free energy
(no energy expended to
diffuse water)
2 factors:
• solute/solvent concentrations
• pressure
http://www.youtube.com/watch?
v=Q_qZLB5CeGk&feature=rela
ted
Water is polar, thus uses a membrane protein to
facilitate osmosis
An aquaporin
A cell’s environment is described in terms of
solute amount, relative to cell contents
Less solute
Hypotonic
equal solute
isotonic
more solute
hypertonic
Describe based on its effect on cells too - flaccid or turgid?
http://www.youtube.com/watch?v=44igB-0PVqA
http://www.youtube.com/watch?v=V4TNL1qIKAQ&NR=1
Cells with a cell wall can handle the pressure
Cells without a wall need a strategy
otherwise the can burst, i.e. RBC
Protists – like Paramecium live in a hypotonic
environment - they
‘bail’ excess water via
the contractile vacuole
http://www.youtube.com/watch?v=9Ynm5ZOW59Q&feature=related
Animals avoid burst cells via osmoregulation
balancing salt & water concentrations of cells & environment
excrete water
drink water
excrete salts
Marine invertebrates
are at equilibrium
with their environment they are salty!
Cartilagenous fish retain
urea, other organics
to lower water potential
of cells
Human excretory system strategy: filter all
reabsorb some
kidney
nephron
http://www.hhmi.org/biointeractive/cardiovascular/kidneyfunction.html
Active transport requires cells expend energy to move
molecules up (against) the concentration gradient
i.e. diffusion &
osmosis
Ex: sodium/potassium
pump
1. Active transport
of ions from soil
2.
Plants use active transport to concentrate minerals
in the root cells, creating a concentration gradient;
water follows via osmosis
Opposite direction
of difusion
Coupled transport
uses a molecule
going down the
gradient to
transport another
against the gradient
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html
Phagocytosis = solids
Pinocytosis = liquids
receptors on CM
can trap target
molecules, trigger
endocytosis
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf
::535::535::/sites/dl/free/0072437316/12
0068/bio02.swf::Endocytosis%20and%2
0Exocytosis