Secondary active transport

Secondary active transport is a type of active transport that moves two different molecules across a transport membrane.One of the molecules is an ion, which moves across the biological membrane, down its  electrochemical gradient. This ion is what allows the other molecule, possible another ion, to move in an uphill direction, against it's concentration gradient. The ion that moves down its concentration gradient is what drives the movement of the other molecule across the membrane. It is because of this that the ion that travels down its concentration gradient is know as the driving ion.

There are two types of secondary active transport. One of which, is where the molecules move in the same direction across the transport membrane, this is known as symport. The other is when the molecules are travelling in the opposite direction to each other, this type of secondary active transport is known as antiport.