Active and passive transport are two biological processes which are occurring all the time in the cells and body. These processes provide oxygen and other nutrients to the cells and remove waste materials from the body. But both processes differ from each other on the basis of gradient and expense of energy.
In active transport, nutrients move from low concentrated region to high concentrated region on the expense of energy whereas, in passive transport, nutrients move from high concentration to low concentration without the use of energy. In active transport, molecules move against the concentration gradient whereas, in passive transport, molecules move along the concentration gradient to stable the equilibrium.
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Comparison Chart
| Basis | Active Transport | Passive Transport |
| Definition | Active transport is a biological process in which nutrients move from low concentration to the high concentration by the use of cellular energy | Passive transport is a biological process in which nutrients move from high concentration to the low concentration without the use of any cellular energy. |
| Direction of movement | From low concentrated environment towards the high concentrated environment | From a high concentrated environment towards the low concentrated environment |
| Type of transported molecules | Ions, Amino acids, Proteins, large molecules, sugar molecules (polysaccharides) | Monosaccharaides, water, oxygen, carbon dioxide, sex hormones |
| Energy Requirement | Use ATP as energy | No need of energy |
| Examples | Endocytosis, exocytosis, Phagocytosis, Pinocytosis, sodium potassium pump, sodium calcium pump etc | Osmosis, diffusion and facilitated diffusion, Filtration |
| Purpose | Carry the molecules through the cell membranes | Maintains the equilibrium gradients inside the cells |
What is Active Transport?
Active transport is the process of transport of nutrients, water, ions, and different molecules across the cell membrane from low concentration to the high concentration area (against the concentration gradient) with the help of enzymes and energy (ATP). It is basically involved in the transport of molecules through the cell membrane which is made up of phospholipids.
Active transport is of two types; primary active transport and secondary active transport. Primary active transport uses direct chemical energy or ATP to push the molecules. In it, molecules to be transported presently in extracellular fluid are recognized by the transmembrane proteins which are run by the ATP. Primary active transport occurs in the sodium-potassium pump which is present in the lining of the stomach and regulates the resting potential of the cells. It transports actively the sodium ions from low concentrated region 11 mM to a higher concentration of 146 mM with the potassium transport outside the cell.
Secondary active transport, the electromagnetic gradient is used to transport across the cell membrane and multiple processes of transport are involved at the same time. For example, SGLT2, a glucose transporter, allows sending glucose molecules into the cells by bringing the sodium with it as well against a concentration gradient. The energy released by the sodium is used to power this process.
Endocytosis and exocytosis are utilized by the cell for transportation of the nutrients which cannot passively permeate through the cell membrane. In endocytosis, molecules move in the cells by the action of engulfing it along the cell membrane. In exocytosis is a counter function of endocytosis for forcing the molecules out of the cell.
What is Passive Transport?
In passive transport, molecules move along the concentration gradient without the use of cellular energy. It uses natural entropy until the concentration across both sides becomes balanced. Simple diffusion facilitated diffusion, osmosis and filtration are four basic types of passive transport. In simple diffusion, non-polar molecules move through the permeable membrane from a higher concentration area to the lower concentration area to maintain equilibrium. In facilitated diffusion, molecules are facilitated to move through the pores or channels which are made from glycoproteins. These pores are present in cell membranes and very specific for the molecules of the certain ions or molecules and thus perform certain functions. For example, GLUT4 is a glucose transporter which is present in fat and skeletal muscles. Insulin triggers it to insert into the membranes of these cells so that glucose can be taken from the blood. It is helpful in preventing heart disease, stroke, and kidney failure by decreasing the level of glucose in the blood.
In osmosis, water molecules are transported through the cell membrane. Many factors affect this transport such as less negative water potential, the solute potential of molecules and pressure potential of the membrane. Filtration is also a type of passive transport for example cardiovascular system of the human body creates hydrostatic pressure which aids to transport water and other molecules in soluble form across the cell membrane. In this, only soluble molecules can move across the cell membrane through the pores so it is called filtration.
Key Differences between Active and Passive Transport
- Active transport necessitates energy whereas passive transport does not need energy.
- Active transport is a unidirectional process whereas passive transport is a bidirectional process.
- Active transport is a dynamic process whereas passive transport is a physical process.
- Active transport is influenced by environmental factors such as temperature, oxygen whereas passive transport is not influenced by temperature and oxygen.
- Active transport requires carrier proteins whereas passive transport requires does not require carrier proteins.
- Active transport is stopped by the metabolic inhibitors whereas passive transport is not affected by the metabolic inhibitors.
- Active transport is a rapid and selective process whereas passive transport is a slow and non-selective process.
- The basic purpose of active transport is the transport of various molecules in the cell whereas passive transport maintains the equilibrium within the cell.
Key Similarities
- Both active and passive transport is involved in the transport of chemical species from one area of the cell to the area.
- Both work with the concentration gradient.
Conclusion
It has concluded from all above discussion that active transport and passive transport are processes occurring in the cells all the time and differ basically from each other on the basis of the movement of molecules along concentration gradient and against a concentration gradient.