Plasma membrane

Surface Area to Volume ratio explained

Here are some great short animations to help you understand these processes:

Diffusion:

Animation: how diffusion works

http://esminfo.prenhall.com/science/BiologyArchive/lectureanimations/closerlook/diffusion.html

http://www.stolaf.edu/people/giannini/flashanimat/transport/diffusion.swf

Osmosis:
http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

http://highered.mheducation.com/sites/9834092339/student_view0/chapter38/animation_-_osmosis.html

http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf

Facilitated Diffusion:
http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

Active Transport:
http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

http://sites.sinauer.com/neuroscience5e/animations04.02.html

Secondary Active Transport:
http://highered.mheducation.com/sites/9834092339/student_view0/chapter5/secondary_active_transport.html

Endocytosis and Exocytosis:
http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio02.swf::Endocytosis+and+Exocytosis

Diffusion and Osmosis – Interactive.  Participation required!

Sodium Potassium Pump – Must see animation.

Transport Mechanisms – Interactive animation looks at all the major transport mechanisms.

Carbon Dioxide and Oxygen Diffusion – Explains diffusion of gases.  Also relevant to Breathing unit.

Endocytosis and Exocytosis – Animation
Endocytosis – simplified animation

Passive and Active Transport Mechanisms – a good additional summary video