Osmosis vs Active Transport
Survival of a cell depends on the balance between its internal and external environments. To maintain this balance, cells need to transport substances across or through cell membranes. There are four processes involving to achieve this task, namely; simple diffusion, active transport, osmosis, and phagocytosis.
What is Osmosis?
Osmosis is the net movement of water across semi- permeable membrane using a concentration gradient. It is a special kind of diffusion due to the involvement of semi- permeable membrane, which allows only certain substances to pass across. Because of the involvement of concentration gradient, which is created by the solution, osmosis does not need additional energy. Usually, water molecules pass across the membrane through the process of osmosis. Osmosis is a very important process occurring in living cells. If the body fluids such as blood and tissue fluid become diluted, water will start to enter into cells by osmosis. In this case, cells swell and eventually burst. On the other hand, if the body fluids become too concentrated, water inside the cells will start to go into body fluids by osmosis, resulting in cell shrinkage. However, the body has certain mechanisms to maintain these concentrations isotonic to one another.
What is Active Transport?
Sometimes diffusion is too slow or cell need to take or get rid of substances against a concentration gradient. Cells achieve this task by a special process called active transport. Active transport is the movement of substance across the cell membrane against a concentration gradient. Unlike the osmosis, active transport needs a great deal of energy, which has to be obtained from ATP. Active transport is achieved with the help of carrier protein in the plasma membrane. Usually the ions like Na+, Cl– and K+, and the molecules like glucose, amino acids, and vitamins are transported by active transport. For example, plants absorb mineral ions by using active transport. In animals, active transport is used to absorb sugar from the gut and kidney back into the blood.
What is the difference between Osmosis and Active Transport?
• Osmosis is the net movement of water down the concentration gradient, whereas active transport is the movement of substances against the concentration gradient.
• Osmosis does not require energy, whereas active transport does.
• Osmosis occurs through semi-permeable membranes, whereas active transport occurs through membranes.
• Diffusion of water occurs through osmosis, whereas transport of ions (Na+, Cl- and K+) and molecules (glucose, amino acids and vitamins) occurs through active transport.