Active Transport

Bob Vickery vickery at MPX.COM.AU
Tue Sep 14 02:56:24 EST 1999


James Perry wrote: 

>Is anyone aware of a lab experiment/exercise on active transport suitable 
>for introductory (first semester/first year) students? Something that does 
>not take $$$$$ for equipment. (There was a British film on an experiment 
>several years ago that was impossible to follow.)
>
>jim
>
>James. W. Perry, CEO/Campus Dean
>Professor, Department of Biological Sciences
>University of Wisconsin - Fox Valley
>1478 Midway Road
>Menasha, Wisconsin 54952-1297
>Office: 920.832.2610
>FAX: 920.832.2674
>jperry at uwc.edu

I would suggest an exercise with root exudates.  Use sunflowers about 6 weeks old grown in solution culture. Decapitate the plants below the cotyledonary node and make a well on the stump with masking tape. Temperature affects the rate of flow so the roots should be kept at about 20 C. It is fairly easy to measure rates of flow and differences in pH and voltage between the solution and the top of the stump.  If you have a flame photometer you can measure concentrations of Na and K.  The rates of flow and the voltages vary quite a bit during the day.  

While this demonstration shows many of the features of active transport it is not suitable for a strict thermodynamic proof because the roots are never in equilibrium or a steady state.

Cheers

Bob Vickery
vickery at mpx.com.au



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