The cell is a dynamic center where there are many processes and functions occurring simultaneously. For this purpose, there is need for substances and end products of metabolic processes to move in and out of the cell. Active transport process is the movement of a substance against the concentration gradient. Thus, this is an important process in biology that requires energy. In most cells, this is usually concerned with accumulating high concentrations of molecules in the cell which it needs, like ions, glucose, amino acids, etc. Active transport involves the transportation of substances from a region of its lower concentration to a regions of its higher concentration. If the process uses chemical energy, such as that which is derived from adenosine triphosphate (ATP), it is termed as primary active transport in cells. Secondary active transport, on the other hand, involves the use of an electrochemical gradient. The main difference between active transport and passive transport is that active transport process uses energy, unlike passive transport, which does not require any energy. Examples of active transport in humans includes the uptake of glucose in the intestines and the uptake of mineral ions into root hair cells of plants.
What is Active Transport Process?
So, how does the process of active transport take place? When a substance has to be actively transported to and from a cell, there are specialized trans-membrane proteins that recognize the substance and allow it access across the membrane when it otherwise would not. This would happen because either it is one to which the lipid bilayer of the membrane is impermeable or because it is being moved against the direction of the concentration gradient. The latter case, known as primary active transport process generally has proteins involved in it as pumps and normally uses the chemical energy of ATP. The other cases, which usually derive their energy through exploitation of an electrochemical gradient that is present, are known as secondary active transport and involve proteins that separate to form channels or pores through the cell membrane to allow passage of substances through the cell membrane. Read more on cell membrane function.
Sometimes the system transports one substance in one direction, while at the same time, co-transporting another substance in the other direction. This is known as antiport. Symport is the name given to a transport process where two substrates are being transported in the same direction across the membrane. Antiport and symport are associated with secondary active transport, that is, one of the two substances are transported in the direction of their concentration gradient utilizing the energy derived from the transport of the second substance, generally a proton, down its concentration gradient.
Particles moving from areas of low concentration to areas of high concentration, that is, in the opposite direction as that of the concentration gradient, require the presence of very specific trans-membrane carrier proteins. These proteins have receptors that bind to specific molecules, like glucose and thus, transport them into the cell. As energy is required for this process to take place, it is known as active transport. Examples of active transport include the transportation of sodium out of the cell and potassium into the cell, which is carried out by the sodium-potassium pump.
This was all about the process of active transportation. Active transport is a very important process, as it is required by cells to maintain their normal state of homeostasis. Active transport process often takes place inside the internal lining of the small intestine. In plants, there is need to absorb mineral salts from the soil but these salts exist in a very minimum concentration. Active transport enables these cells to take up salts from this dilute concentration against the direction of the concentration gradient.