Question

1) Explain the different types of ion channels.

2) Explain in detail the glucose symporter. How does it work and what is its mechanism?

Answer 1

ANSWER 1) The three main groups of ion channels are

1) the voltage-gated channels such as the sodium and potassium channels of the nerve axons and nerve terminals.

2) the extracellular ligand-activated channels which includes channels such as GABA and glycine receptor channels, most of which are regulated by ligands that are "neurotransmitters". These channels are often named according to the ligand they bind to.

3) Intracellular ligand-gated ion channels. These include CFTR and some other ABC family members as well as ion channels involved in sense perception. These are often activated indirectly by GCPRs. Other common intracellular ligands which activate these kinds of channels include calcium ions, ATP, cyclic AMP and GMP as well as phosphadidyl inositol (PI).

ANSWER 2) Sodium-glucose Symporter is a transmembrane protein and is an example of sodium-driven Secondary active transport that occurs in the epithelial cells of the small intestines . The sodium-glucose symporter is found on the Apical membrane of the epithelal cells. The sodium and glucose bind to the symporter and are simultaneously both co-transported into the epithelial cells. The sodium driven-glucose symporter uses the potential free energy stored in the sodium electrochemical gradient (low sodium concentration inside the epithelial cells) established by Sodium-potassium pump. Therefore, the sodium influx from the lumen to the epithelial cell is coupled with glucose transport.