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Receptor (biochemistry)
In biochemistry and pharmacology, receptors are chemical structures, composed of protein, that receive and Signal_transduction, transduce signals that may be integrated into biological systems. These signals are typically chemical messengers which bind to a receptor and produce physiological responses, such as a change in the electrophysiology, electrical activity of a cell. For example, GABA, an inhibitory neurotransmitter, inhibits electrical activity of neurons by binding to GABAA receptor, GABA receptors. There are three main ways the action of the receptor can be classified: relay of signal, amplification, or integration. Relaying sends the signal onward, amplification increases the effect of a single ligand (biochemistry), ligand, and integration allows the signal to be incorporated into another biochemical pathway. Receptor proteins can be classified by their location. Cell surface receptors, also known as transmembrane receptors, include ligand-gated ion channels, G prote ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intracellular Receptor
Intracellular receptors are globular protein receptors located inside the cell rather than on its cell membrane. The word ''intracellular'' means "within or inside a cell." Molecules that cross a cell membrane to bind with a receptor are generally nonpolar and may be relatively small. These molecules are also known as ligands, these trigger how genes are turned on or off which are essential for processes like growth metabolism etc. Hormones that use intracellular receptors include thyroid, aldosterone, and steroid hormones. Mechanism of Intracellular Receptors The process starts when a signaling molecule like hormones and binds to a specific receptor. # Binding: the molecule(hormone) bind to the intracellular receptor which changes its shape (induced-fit mechanism) and activates it. # Activation: the intracellular receptor moves to the nucleus if it wasn’t already in the nucleus. # DNA binding: the activated intracellular receptor binds to a specific part of the DNA calle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitropism
Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general feature of all higher and many lower plants as well as other organisms. Charles Darwin was one of the first to scientifically document that roots show ''positive gravitropism'' and stems show ''negative gravitropism''. That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behavior can be easily demonstrated with any potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, growing (biologists say, turning; see tropism) upwards. Herbaceous (non-woody) stems are capable of a degree of actual bending, but most of the redirected movement occurs as a consequence of root or stem growth outside. The mechanism is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanoreceptor
A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are located on sensory neurons that convert mechanical pressure into action potential, electrical signals that, in animals, are sent to the central nervous system. Vertebrate mechanoreceptors Cutaneous mechanoreceptors Cutaneous mechanoreceptors respond to mechanical stimuli that result from physical interaction, including pressure and vibration. They are located in the skin, like other cutaneous receptors. They are all innervated by Aβ fibers, except the mechanorecepting free nerve endings, which are innervated by A delta fiber, Aδ fibers. Cutaneous mechanoreceptors can be categorized by what kind of sensation they perceive, by the rate of adaptation, and by morphology. Furthermore, each has a different receptive field. By sensation * The Slowly Adapting type 1 (SA1) mechanoreceptor, with the Merkel corpuscle end-organ (also known as M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemoreceptor
A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance ( endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemoreceptor is a neuron, or in the form of a neurotransmitter that can activate a nerve fiber if the chemoreceptor is a specialized cell, such as taste receptors, or an internal peripheral chemoreceptor, such as the carotid bodies. In physiology, a chemoreceptor detects changes in the normal environment, such as an increase in blood levels of carbon dioxide (hypercapnia) or a decrease in blood levels of oxygen (hypoxia), and transmits that information to the central nervous system which engages body responses to restore homeostasis. In bacteria, chemoreceptors are essential in the mediation of chemotaxis. Cellular chemoreceptors In prokaryotes Bacteria utilize complex long helical proteins as chemoreceptors, permitting signals to travel lon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecules known as product (chemistry), products. Almost all metabolism, metabolic processes in the cell (biology), cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme, pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts include Ribozyme, catalytic RNA molecules, also called ribozymes. They are sometimes descr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curare
Curare ( or ; or ) is a common name for various alkaloid arrow poisons originating from plant extracts. Used as a paralyzing agent by indigenous peoples in Central and South America for hunting and for therapeutic purposes, curare only becomes active when it contaminates a wound or is introduced directly to the bloodstream; it is not active when ingested orally. Curare is prepared by boiling the bark of one of the dozens of plant sources, leaving a dark, heavy paste that can be applied to arrow or dart heads. These poisons cause weakness of the skeletal muscles and, when administered in a sufficient dose, eventual death by asphyxiation due to paralysis of the diaphragm. In medicine, curare has been used as a treatment for tetanus and strychnine poisoning and as a paralyzing agent for surgical procedures. History The word 'curare' is derived from , from the Carib language of the Macusi of Guyana. It has its origins in the Carib phrase "mawa cure" meaning of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicotine
Nicotine is a natural product, naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and ''Duboisia hopwoodii'') and is widely used recreational drug use, recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is used for smoking cessation to relieve drug withdrawal, withdrawal symptoms. Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits (nAChRα9 and nAChRα10) where it acts as a receptor antagonist. Nicotine constitutes approximately 0.6–3.0% of the dry weight of tobacco. Nicotine is also present at Parts-per notation, ppb concentrations in edible plants in the family Solanaceae, including potatoes, tomatoes, and eggplants, though sources disagree on whether this has any biological significance to human consumers. It functions as an plant defense against herbivory, antiherbivore toxin; consequently, nicotine was widely used as an insecti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetylcholine
Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Parts in the body that use or are affected by acetylcholine are referred to as cholinergic. Acetylcholine is the neurotransmitter used at the neuromuscular junction. In other words, it is the chemical that motor neurons of the nervous system release in order to activate muscles. This property means that drugs that affect cholinergic systems can have very dangerous effects ranging from paralysis to convulsions. Acetylcholine is also a neurotransmitter in the autonomic nervous system, both as an internal transmitter for both the sympathetic nervous system, sympathetic and the parasympathetic nervous system, and as the final product released by the parasympathetic nervous system. Acetylcholine is the primary neurotransmitter of the parasympathet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nicotinic Acetylcholine Receptor
Nicotinic acetylcholine receptors, or nAChRs, are Receptor (biochemistry), receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the agonist nicotine. They are found in the central and peripheral nervous system, muscle, and many other tissues of many organisms. At the neuromuscular junction they are the primary receptor in muscle for motor nerve-muscle communication that controls muscle contraction. In the peripheral nervous system: (1) they transmit outgoing signals from the presynaptic to the postsynaptic cells within the Sympathetic nervous system, sympathetic and parasympathetic nervous system, and (2) they are the receptors found on skeletal muscle that receive acetylcholine released to signal for muscular contraction. In the immune system, nAChRs regulate inflammatory processes and signal through distinct intracellular pathways. In insects, the cholinergic system is limited to the central nervous system. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium-sensing Receptor
The calcium-sensing receptor (CaSR) is a Class C G-protein coupled receptor which senses extracellular levels of calcium ions. It is primarily expressed in the parathyroid gland, the renal tubules of the kidney, pancreatic islets and the brain. In the parathyroid gland, it controls calcium homeostasis by regulating the release of parathyroid hormone (PTH). In the kidney, it has an inhibitory effect on the re-absorption of calcium, potassium, sodium, and water depending on which segment of the tubule is being activated. CaSR has regulatory role in insulin secretion, adhesion and beta-cell proliferation in pancreatic islets. Since the initial review of CaSR, there has been in-depth analysis of its role related to parathyroid disease and other roles related to tissues and organs in the body. 1993, Brown et al. isolated a clone named BoPCaR (bovine parathyroid calcium receptor) which replicated the effect when introduced to polyvalent cations. Because of this, the ability to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hormone
A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physiology and behavior. Hormones are required for the normal development of animals, plants and fungi. Due to the broad definition of a hormone (as a signaling molecule that exerts its effects far from its site of production), numerous kinds of molecules can be classified as hormones. Among the substances that can be considered hormones, are eicosanoids (e.g. prostaglandins and thromboxanes), steroids (e.g. Estrogen, oestrogen and brassinosteroid), amino acid derivatives (e.g. epinephrine and auxin), protein or peptides (e.g. insulin and CLE peptides), and gases (e.g. ethylene and nitric oxide). Hormones are used to communicate between organ (anatomy), organs and Tissue (biology), tissues. In vertebrates, hormones are responsible for regulating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
