a part of amembrane at restshowing the transport of glucose usingthe glucose-Na+symport protein. We knowthat the average mammalian cellhas a cytosol chemicalconcentration of roughly15mM ofNa+ as compared to itsextracellular concentrationof 154mM. Overall, theelectrical gradient in cells at rest are more negative inside ascompared to outside of the cell.
1.There is strong electrochemical gradient for Na+,explain why this is true (hint, think about whatmakes up the electrochemical gradient).
2.The ion, chloride (Cl-) is more concentrated on the outside(110 mM) than the inside of the cell (15 mM). Do you expect theoverall electrochemical gradient for chloride to be as large as theNa+ electrochemical gradient? Explain why or whynot (hint, think about what makes up the electrochemicalgradient).
3.If the concentration of Na+ increased on the inside of thecell so that it was equal on both sides, would we see an increaseor decrease in the overall electrochemical gradient of Na+ ascompared to the resting cell? Explain youranswer
4.The glucose-Na+ symport protein uses the electrochemicalgradient of Na+ to move glucose against its concentration gradient.Predict whether the transport of glucose from the extracellularside into the cytosol would increase or decrease under thefollowing scenarios:
a.The Na+ electrochemical gradient is greatly reduced.
b. A ligand binds to the symport protein so that the site whichbinds Na+ no longer has a strong affinity for Na+.
the Na+K+ ATPasepump, also known as theNa+ pump.This pump moves bothNa+ andK+ against theirconcentration gradients through the hydrolysis of ATP (here isanother way, ATP, the “currency of the cell†is used).
5. Compare and contrast the properties and the functioning ofthese two types of transporters.
