What is the difference between receptor mediated endocytosis and pinocytosis

These endocytotic vesicles are invaginated from the cell membrane. Small molecules which are suspended in the extracellular fluid are transported through this mechanism. Pinocytosis does not select the molecules to transport. All small molecules in the water are ingested by pinocytosis. Hence, it not a specific process; it is also not an efficient process.

Pinocytosis is a simple mechanism which happens in most of the cells. Pinocytosis is the typical molecule transport mechanism in liver cells, kidney cells, capillary cells and epithelial cells. Receptor mediated endocytosis is a form of endocytosis in which macromolecules are uptaken to the cell selectively from the extracellular fluid.

This mechanism is mediated by the receptors on the cell surface. Receptors recognize specific macromolecules form receptor-macromolecule complexes. These receptor-macromolecule complexes accumulate in the pits which are created from the plasma membrane and coated with clathrin. Then these receptor-macromolecule complexes internalize into clathrin coated vesicles formed from clathrin coated pits. The clathrin-coated vesicles then fuse with early endosomes.

Macromolecule-receptor complexes dissociate in the reduced pH levels of the endosomes; macromolecules are transferred to lysosomes while receptors are returned to the cell surface. Receptor mediated endocytosis is a very specific mechanism of up taking molecules into the cells, unlike pinocytosis. Materials to be transported inside are decided by the receptors present on the cell membrane surface. It is a more efficient process than pinocytosis. Pinocytosis and receptor mediated endocytosis are two types of endocytosis mechanisms which function in most of the cells.

Pinocytosis is a simple process in which extracellular fluid is taken in by the cell without a selection. Receptor mediated endocytosis is a complex process in which macromolecules in the extracellular fluid are identified by cell surface receptors and taken inside the cell by clathrin coated vesicles.

Pinocytosis is a nonspecific process while receptor mediated endocytosis is a specific process. The main importance of this process is that it only allows a small portion of liquid to enter the cell. Also, due to the involvement of clathrin in the process, this type of endocytosis is also called clathrin-mediated endocytosis. Figure 2: Receptor Mediated Endocytosis. In a general sense, receptor-mediated endocytosis is the main method of endocytosis in most types of cells. Some important types of molecules taken up into the cell by this process are hormone-binding molecules, iron-binding proteins like transferrin, low-density lipoprotein cholesterol carriers, etc.

Pinocytosis refers to the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane while receptor-mediated endocytosis refers to an endocytotic mechanism in which specific molecules are ingested into the cell.

Thus, this is the main difference between pinocytosis and receptor mediated endocytosis. Moreover, pinocytosis is also called cell drinking while receptor-mediated endocytosis is also called clathrin-mediated endocytosis. Furthermore, pinocytosis mainly uptakes liquids while receptor-mediated endocytosis mainly uptakes solutes.

Another difference between pinocytosis and receptor mediated endocytosis is that the receptors do not involve in pinocytosis while the receptors on the cell membrane do involve in receptor-mediated endocytosis. Also, selectivity is a major difference between pinocytosis and receptor mediated endocytosis. Pinocytosis is not a selective process while receptor-mediated endocytosis is a selective process.

Besides, solutes in the extracellular fluid enter into the cell through pinocytosis while selected solutes bind to the receptors and enter the cell during receptor-mediated endocytosis. The cell does this by forming narrow channels through its membrane.

These channels surround the liquid and all its contents and then pinch off into vesicles, hence the liquid in successfully absorbed into the cell. The molecules then fuse with lysosomes to hydrolyze or be broken down. The process of pinocytosis requires a lot of energy in the form of adenosine triphosphate. This is the chemical compound that is generally used as energy in most cells.

Receptor-mediated endocytosis RME is the process by which a cell absorbs nutrients into the cell. The cell membrane is lined with receptors which seek their compatible nutrients or molecules. Once they find the nutrient, the receptors receive a signal through the membrane.

The process then leads to a membrane coating. The receptors, now coated will now attach to the molecule. The plasma membrane will then surround the molecule, which will then be absorbed into the cell via a vesicle.