Human body is a complicated network of cells, molecules and numerous other components. There is a wide variety of interesting interactions and movement of molecules between the constituent components. Active and passive transport are two of such interactions. Transport refers to the movement of molecules and other materials in and from out of the cells of a human body or any living organism.
Active Transport and Passive Transport:
Active and passive transport are both biological process which involve movement of oxygen molecules, water and other nutrients that are required for the normal functioning of the cell into the cell and removing any waste products that the cells produce. These terms refer to any activity which moves molecules through a concentration gradient. Concentration gradient can be defined as a situation which occurs when there is a difference in the concentration of a solution as a consequence of an unequal distribution of ions across a cell membrane.
- Active transport refers to a movement of a molecule or a solute from a region with lower concentration of ions to a region with a higher concentration of ions. Passive transport is the movement of molecules or solute from a region with higher concentration of ions to a region with lower concentration of ions.
- The active transport is against the concentration gradient while passive transport is with the flow of the concentration gradient. Active transport for its flow against the gradient encounters resistance and needs energy to overcome it. While passive transport requires no energy for the movement as there is no resistance.
- In active transport there is a higher concentration of molecules either inside (when nutrients are moved) or outside the cell (when wastes are moved) than the normal state thus disrupting the equilibrium. In passive transport there is no disruption to the equilibrium and there is a perfect equilibrium of water, gases and nutrients maintained between the cells and the extra cellular fluid.
- One of the main differences between the two transport systems is the energy that is required by the active transport for executing the process. This energy is known as Adenosine Triphosphate (ATP). Active transport requires this cellular energy while passive transport does not need cellular energy.
- Active transport helps in moving particles such as proteins, ions, large and complex sugars and cells. Passive transport moves smaller and easily dissolvable particles such as monosaccharide, water, oxygen, carbon dioxide, sex hormones among others.
- Active transport helps in diffusion of particles which diffuse very easily or takes a long time to diffuse. Passive transport is important in maintaining equilibrium in the cells by diffusing wastes out and diffusing nutrients in to the cell.
- There are two types of active transport – primary and secondary .Types of active transport are Endocytosis, cell membrane/sodium-potassium pump and exocytosis. The different types of passive transport are diffusion, facilitated diffusion and osmosis.
- In cells with membranes molecules of amino acids, sugars and lipids enter into the cells with the help of protein pumps which is an active transport. Passive transport is observed when wastes are diffused out of cells for excretion and nutrients are diffused inside cells for cellular functions.
- Examples of active transport are sodium/potassium pump, glucose selection by the intestines and absorption of minerals by the roots of the plants. Passive transport occurs when oxygen is taken in and carbon di oxide is exhaled out through the lungs of humans.
Though generally the biological terms active and passive transport are associated with only the interactions and movements within the human body these terms are also used to depict the movement of molecules in plants and animals too.