Active Transport

• Active transport is the process which moves substances against their concentration gradient. This means that substances are transported from an area of lower concentration to an area of higher concentration.
• This process requires energy, supplied by Adenosine Triphosphate (ATP). ATP is a molecule that stores and releases energy as needed by the cell.
• Examples of substances that might be transported this way include ions, glucose and amino acids.
• Active transport utilises carrier proteins which are found in cell membranes. These proteins change their shape to move molecules across the membrane.
• This process allows cells to absorb ions from very dilute solutions. For example, root hair cells in plants use active transport to obtain nitrates from the soil.
• Active transport plays an important role in the functioning of the human body. For instance, the sodium-potassium pump, which maintains the electrical balance in nerve cells, relies on active transport.
• It also enables sugar molecules to be absorbed from the gut and from kidney tubules back into the blood, which would be impossible by diffusion alone due to the usually higher concentration of these molecules in the blood.
• Remember, because active transport uses energy, it can still take place even when a cell is not actively dividing or growing.
• The rate of active transport can be affected by factors such as temperature and the availability of ATP. If a cell does not have enough ATP, it cannot carry out active transport.
• Active transport should not be confused with passive transport. The key difference is that passive transport does not require any energy as it moves substances along their concentration gradient, from an area of high concentration to an area of low concentration.