The program simulates experiments designed to demonstrate by investigation the important characteristics of the transport of two important nutrients - hexoses and amino acids, in the small intestine.

INTRODUCTION and METHODS use a combination of text and high-resolution graphics to explain the process of carrier-mediated transport of these nutrients, the everted sac preparation and the methods used to measure nutrient transport: using radio labelled galactose, glycine and methionine and a scintillation counting technique; measuring the transmural potential difference particularly for kinetic analysis of the transport system.

EXPERIMENTS allows the user to collect sample data from a range of experiments designed to:

1. Measure the transport of each of these nutrients - Control experiments;

2. Demonstrate the Na+ dependence of the transport process by measuring transport of each nutrient when the mucosal fluid contains reduced concentrations of sodium ions (NaCl partly replaced with KCl/tris chloride/choline chloride); investigate the mutual interaction of the hexose and amino acid transport systems by performing a series of experiments (including a kinetic analysis and calculation of apparent Km and Vmax for the transport process) to assess whether the interaction is due to competition for energy or competition at the carrier level.

Students are presented with raw data: weights: wet empty sac; weight of sac containing 0.5ml Krebs bicarbonate saline; wet weight after incubation in mucosal fluid containing a nutrient; wet weight of final empty sac; radioactive counts) cpm, ESR, dpm, blank- corrected dpm): blank; control sample; serosal sample, gut sample. The data is based on predictive models of carrier-mediated transport, which have been verified by experiment. Students collect the data and use them to calculate transport parameters e.g. mucosal fluid transfer, total amount of nutrient transferred, final gut concentration and T/M ratio, in much the same way as they would if they performed the experiment for real.

System Requirements: Windows: Intel Pentium II 450MHz or faster processor (or equivalent), 128MB of RAM; Microsoft Windows 98, Windows Me, Windows 2000, Windows XP or Windows Server 2003 Macintosh: PowerPC G3 500MHz or faster processor, 128MB of RAM; Mac OS X v.10.1.x, 10.2.x, 10.3.x, or 10.4.x

Recommended browser software: Windows: Internet Explorer; Macintosh: Safari or Firefox; Both: Adobe Flash Player plug-in, version 8 or higher.

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