What is the major difference between primary and secondary active transport mechanisms?

Major difference between 2 types of active transport: Source of energy

• Primary active transport - chemical energy - ATP
• Secondary active transport - electrochemical gradient energy

Step-by-step explanation

The major difference between a primary and secondary active transport mechanisms is their source of energy for the transport of substances. Primary transport mechanisms directly uses chemical energy in the form of ATP to transport molecules against their concentration gradient. Secondary transport, on the other hand, uses energy from the electrochemical gradient which was generated by primary active transport.

Below are examples of primary and secondary active transport and how energy is used during these transports:

Primary active transport : sodium-potassium pump

The pump uses ATP to transport 3 sodium ions and then 2 potassium ions against the concentration gradient.

Secondary active transport: sodium-glucose cotransporter

It is called a cotransporter since the transport of one molecule is coupled with the transport of another molecule. As we can see in the image, secondary transport utilizes the electrochemical gradient of sodium ions (which was generated by primary transport) to transport glucose against it concentration gradient.

Please see the attached file for the complete solution