Active transport is the movement of solutes such as glucose, amino acids and mineral ions;
From an area of their low concentration to an area of high concentration
It is movement against a concentration gradient and therefore energy is required
As such it only takes place in living organisms
The energy needed comes from respiration
Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins
The shape of each type of carrier protein is specific to the type of substances conveyed through it
It has been shown that the substance fits into a particular slot on the protein molecule,
As the protein changes from one form of shape to another the substance is moved across and energy is expended