Difference between Active and Passive Transport
Active and Passive transport are biological transport processes that involve transport of molecules across the cell membrane of cells in living organisms. A cell membrane is a semipermeable membrane that surrounds the cell and separates its cytoplasm (contents of the cell) from the extracellular environment. Let us see how Active transport differs from Passive transport.
Active Transport
Active transport is the movement of molecules across the membrane against the concentration gradient (from a region of lower concentration to a region of higher concentration) using cellular energy in the form of ATP. It is called ?active? because it involves the use of energy, e.g. energy is used by the cell in the form of ATP (Adenosine Triphosphate) to carry out movement of substances into the cell through cellular membrane. Endocytosis, exocytosis, sodium-potassium pump are few examples of active transport.
Active transport can be of two types: primary active transport and secondary active transport. When the active transport occurs using cellular energy in the form of ATP it is known as primary active transport. The active transport in which proteins in the cell membranes uses an electrochemical gradient to move molecules across the membrane is called secondary active transport. The energy comes from the electrochemical gradient created by pumping ions out of the cell.
Passive Transport
Passive transport is the movement of molecules across the membrane along the concentration gradient, from high to low concentration, without using cellular energy. In passive transport, a substance tends to diffuse from a region of higher concentration to a region of lower concentration.
It occurs spontaneously so it does not require cellular energy. In passive transport natural entropy is used to move molecules from their higher concentration to lower concentration until equilibrium is achieved.
Easy soluble particles are transported through passive transport, e.g. wastes like water or carbon dioxide are moved out, and nutrients and oxygen are moved into the cells through passive transport. Its common examples include diffusion, osmosis, and facilitated diffusion.
Based on the above information, some of the key differences between active transport and passive transport are as follows:
| Active Transport | Passive Transport |
|---|---|
| It requires cellular energy in the form of ATP molecules to transfer molecules across the cell membrane. | It does not require cellular energy to transfer molecules across the cell membrane. |
| Molecules are transported against the concentration gradient, from low to high concentration. | Molecules are transported along the concentration gradient from high to low concentration. |
| Molecules move across the cell membrane, disrupt the equilibrium between cytoplasm and extracellular environment. | It creates a dynamic equilibrium of water, nutrients, gasses and wastes between cytoplasm and extracellular environment. |
| Ions, large cells, complex sugars and large proteins are transported. | Lipids, carbon dioxide, water, oxygen and small monosaccharides are transported. |
| It is required to transfer large, insoluble molecules like sugars, lipids, amino acids into the cell. | It is required to maintain the homeostasis between the cytoplasm and extracellular environment e.g. wastes like carbon dioxide and water move out of the cell and nutrients and oxygen move into the cell. |
| It is a vital process. | It is a physical process. |
| It requires carrier proteins, the matrix is not involved. | It takes place through the matrix, carrier proteins are not required. |
| It is highly selective, selected molecules transported into the cell. | It is partially non-selective. All diffusible substances can be transported in or out of the cell along the concentration gradient. |
| It is a rapid process. | t is a comparatively slow process. |
| It is a unidirectional process, occurs in one direction. | It is a bidirectional process. |
| It slows down or stops with oxygen deficiency. | It is not affected by the oxygen deficiency. |
| It is stopped by metabolic inhibitors. | It is not affected by metabolic inhibitors. |
| It tends to decrease with increasing temperature. | It is not affected by the temperature. |
| Examples include endocytosis, exocytosis, sodium/potassium pump, secretion of substances into the bloodstream. | Examples include osmosis, diffusion, and facilitated diffusion. |