Question

Are voltage gated sodium channels, and voltage gated potassium channels considered secondary active transporters? If not then what are they called, and could you please explain what a secondary active transporter is and include a common example of one?

Answer 1

Voltage gated sodium channels, and voltage gated potassium channels are not considered secondary active transporters, rather they are primary active transporters. Primary active transport is coupled directly with a metabolic source of energy, such as ATP hydrolysis.

Secondary active traspoerter performs secondary active (indirect) transport when endergonic (uphill) transport of one solute is coupled with the exergonic (downhill) flow of a different solute that was originally pumped uphill by primary active transport. Secondary active transporter is either symport or antiport, depending on whether the two solutes move in the same or opposite directions.

Figure- Comparison of primary and secondary active transporters.

A common example of secondary active traspoerter is Na⁺- glucose transporter ( also known as sodium-glucose symporter). The Na⁺ flows down their concentration gradient while the glucose molecules are transported against their concentration gradient into the cell. Later the Na⁺ is pumped back out of the cell by the Na⁺- K⁺ ATPase and thus maintaining the inward sodium gradient.

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