Functional proteinaceous structures typically found in the membrane (surface) of cells that tightly bind specific molecules (organic, proteins or viruses). Some (relatively rare) receptors are located inside the cell’s membrane (e.g., free-floating receptor for Retin-A). Both (membrane, internal) types of receptors are a functional part of information transmission to the cell. A general overview is that once bound, both the receptor and its “bound entity” as a complex is internalized by the cell via a process called endocytosis, in which the cell membrane in the vicinity of the bound complex invaginates. This process forms a membrane “bubble” on the inside of the cell, which then pinches off to form an endocytic vesicle. The receptor then is released from its bound entity by cleavage in the cell’s lysosomes. It is recycled (returned) to the surface of the cell (e.g., low-density lipoprotein receptors). In some cases the receptor, along with its bound molecule may be degraded by the powerful hydrolytic enzymes found in the cell’s lysosomes (e.g., insulin receptors, epidermal growth factor receptors, and nerve growth factor receptors). Endocytosis (internalization of receptors and bound ligand such as a hormone) removes hormones from the circulation and makes the cell temporarily less responsive to them because of the decrease in the number of receptors on the surface of the cell. Hence the cell is able to respond (to new signal). A receptor may be thought of as a butler who allows guests (in this case molecules that bind specifically to the receptor) to enter the house (cell) and who accompanies them as they enter. Another mode of “reception” occurs when, following binding, a transmembrane protein (e.g., one of the G proteins) activates the portion of the transmembrane (i.e., through the cell membrane) protein lying inside the cell. That “activation” causes an effector inside cell to produce a “signal” chemical inside the cell which causes the cell to react to the original external chemical signal (that bound itself to the receptor portion of the transmembrane protein).
Protein (often a membrane protein) that has a binding site for another molecule (“ligand”); important for signal transduction in cells.
A structure on a cell that can be stimulated by a specific hormone or chemical to cause a biological response.
Specific sites on or within the brain or other organ or cell to which molecules attach in order to produce a particular effect.
A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific physiologic effect in the cell.
A specialized area on a nerve membrane, a blood vessel, or a muscle that receives the chemical stimulation that activates or inhibits the nerve, blood vessel, or muscle.
A nerve ending or cell which senses a change such as cold or heat in the surrounding environment or in the body and reacts to it by sending an impulse to the central nervous system.
This is a general term applied to any protein in any part of the cell that binds to a specific compound and allows that compound to do its job in the cell. Most hormones and many nutrients have specific receptors, without which these hormones or nutrients would be ineffective. The term also refers to proteins in the nucleus and mitochondria that have a specific role in binding nutrients, hormones, or metabolites to specific base sequences in the DNA in these compartments. There are both plasma and intracellular membrane receptors. Plasma membrane receptors typically bind peptides or proteins. These are called ligands.
The component of the cell (usually a protein) to which the drug binds, thus initiating a change in cell function.
Ending of a sensory nerve, specialized to detect changes and trigger impulses in the sensory nerve (e.g., cells at the end of the olfactory nerve that detect odors in the nasal cavity).
A sensory nerve ending that receives a chemical message by linking or binding to a specific factor, drug, hormone, antigen, or neurotransmitter.
Cellular surface structures that combine with antigens or other substances and thereby acquire new properties.
A nerve cell that responds to a stimulus in the environment by producing nerve impulses. The term “receptor” may also refer to the area on the surface of a cell to which a chemical must bind to have its effect.
A cell or group of cells specialized to detect changes in the environment and trigger impulses in the sensory nervous system. All sensory nerve endings act as receptors, whether they simply detect touch, as in the skin, or chemical substances, as in the nose and tongue, or sound or light, as in the ear and eye.
In cell biology, a structure in the cell membrane or within a cell that combines with a drug, hormone, chemical mediator, or an infectious agent to alter an aspect of the functioning of the cell.
The points on a cell where drug chemicals or neurotransmitters attach.
A cellular component, often a proteinaceous entity, residing either within or on the cell’s exterior, which forms a connection with a distinct chemical group or molecule, such as a hormone or growth factor, in order to commence a series of orchestrated actions.
A receptor refers to a type of sensory nerve cell that transforms external stimuli into nerve signals. The term is also used to describe specialized structures on a cell’s surface that enable chemicals to attach to the cell, allowing them to produce specific effects.
The endings of nerves located in the skin and specific sensory organs.
A side chain or haptophore group present in every tissue cell, alongside the nucleus. This group binds with intermediary entities like toxins, food molecules, and foreign materials, and is integral to the side-chain theory.