Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3'-5'-cyclic adenosine monophosphate) is a second messenger important in many biological processes. cAMP is derived from adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway.
Calreticulin is a multifunctional protein that binds Ca ions, rendering it inactive. The Ca is bound with low affinity, but high capacity, and can be released on a signal. Calreticulin is located in storage compartments associated with the endoplasmic reticulum. Calreticulin is also known as calregulin, CRP55, CaBP3 and calsequestrin-like protein. The term "Mobilferrin" is considered to be the same as calreticulin by some sources.
G proteins, short for guanine nucleotide-binding proteins, are a family of proteins involved in second messenger cascades. G proteins are so called because they function as "molecular switches". They alternate from 'inactive' guanosine diphosphate (GDP) to 'active' guanosine triphosphate (GTP), which is a binding state, and which proceeds to regulate downstream cell processes. G proteins were discovered when Alfred G. Gilman and Martin Rodbell investigated stimulation of cells by adrenaline.
A hormone (from Greek ὁρμή - "impetus") is a chemical released by a cell in one part of the body, that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms produce hormones; plant hormones are also called phytohormones. Hormones in animals are often transported in the blood.
A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances. There are four major classes, termed A, B, C and D distinguished by what type of reaction they catalyze: Phospholipase A Phospholipase A1 - cleaves the SN-1 acyl chain Phospholipase A2 - cleaves the SN-2 acyl chain, releasing arachidonic acid Phospholipase B - cleaves both SN-1 and SN-2 acyl chains, also known as a lysophospholipase.
Chemical synapses are specialized junctions through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie perception and thought. They allow the nervous system to connect to and control other systems of the body.
Serotonin or 5-Hydroxytryptamine (5-HT) is a monoamine neurotransmitter that is primarily found in the gastrointestinal (GI) tract and central nervous system (CNS) of humans and animals. Approximately 80 percent of the human body's total serotonin is located in the enterochromaffin cells in the gut, where it is used to regulate intestinal movements.
In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another. Most processes of signal transduction involve ordered sequences of biochemical reactions inside the cell, which are carried out by enzymes and activated by second messengers, resulting in a signal transduction pathway.
File:Merge-arrows. svg It has been suggested that this article or section be merged with Protein phosphorylation. Phosphorylation is the addition of a phosphate (PO4) group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes, causing or preventing the mechanisms of diseases such as cancer and diabetes. Protein phosphorylation in particular plays a significant role in a wide range of cellular processes.
In biochemistry, a macromolecule exhibits cooperative binding if its affinity for its ligand changes with the amount of ligand already bound. Cooperative binding is a special case of allostery. Cooperative binding requires that the macromolecule have more than one binding site, since cooperativity results from the interactions between binding sites. If the binding of ligand at one site increases the affinity for ligand at another site, the macromolecule exhibits positive cooperativity.
File:Flexibility of Calmodulin. png Flexibility of Calmodulin. Calmodulin can bind to calmodulin-dependent-protein kinase II-alpha (upper left, PDB code=1cm1); it can bind to myosine light chain (lower left, 2bbm); it can bind to edema factor toxin from the anthrax bacteria (right, 1k93) more details... Calmodulin (CaM) (an abbreviation for CALcium MODULated proteIN) is a calcium-binding protein expressed in all eukaryotic cells.
protein kinase A (PKA) refers to a family of enzymes whose activity is dependent on the level of cyclic AMP (cAMP) in the cell, in cell biology. PKA is also known as cAMP-dependent protein kinase EC 18.104.22.168). Protein kinase A has several functions in the cell, including regulation of glycogen, sugar, and lipid metabolism. It is important in regulating cell cycle, along with the protein cyclin.
A gap junction or nexus is a specialized intercellular connection between a multitude of animal cell-types. It directly connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells. One gap junction is composed of two connexons (or hemichannels) which connect across the intercellular space. Gap junctions are analogous to the plasmodesmata that join plant cells. A notable use of gap junctions is in the electrical synapse found in some neurons.
Sonic hedgehog homolog (SHH) is one of three proteins in the mammalian signaling pathway family called hedgehog, the others being desert hedgehog (DHH) and Indian hedgehog (IHH). SHH is the best studied ligand of the hedgehog signaling pathway. It plays a key role in regulating vertebrate organogenesis, such as in the growth of digits on limbs and organization of the brain.
The NMDA receptor (NMDAR), a glutamate receptor, is the predominant molecular device for controlling synaptic plasticity and memory function. The NMDAR is a specific type of ionotropic glutamate receptor. NMDA (N-methyl D-aspartate) is the name of a selective agonist that binds to NMDA receptors but not to other glutamate receptors. Activation of NMDA receptors results in the opening of an ion channel that is nonselective to cations.
Cooperativity is a phenomenon displayed by enzymes or receptors that have multiple binding sites where the affinity of the binding sites for a ligand is increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to a binding site- for example: the affinity of hemoglobin's four binding sites for oxygen is increased above that of the unbound hemoglobin when the first oxygen molecule binds. This is referred to as cooperative binding.
5' AMP-activated protein kinase or AMPK or 5' adenosine monophosphate-activated protein kinase is an enzyme that plays a role in cellular energy homeostasis. It consists of three proteins that together make a functional enzyme, conserved from yeast to humans. It is expressed in a number of tissues, including the liver, brain, and skeletal muscle.
Membrane potential (or transmembrane potential) is the voltage difference between the interior and exterior of a cell. All animal cells are surrounded by a plasma membrane composed of a lipid bilayer with many diverse protein assemblages embedded in it. The fluid on both sides of the membrane contains high concentrations of mobile ions, of which sodium (Na), potassium (K), chloride (Cl), and calcium (Ca) are the most important.
In biochemistry, a receptor is a protein molecule, embedded in either the plasma membrane or the cytoplasm of a cell, to which one or more specific kinds of signaling molecules may attach. A molecule which binds (attaches) to a receptor is called a ligand, and may be a peptide (short protein) or other small molecule, such as a neurotransmitter, a hormone, a pharmaceutical drug, or a toxin. Each kind of receptor can bind only certain ligand shapes.
Cyclin-dependent kinases (CDK) belong to a group of protein kinases originally discovered as being involved in the regulation of the cell cycle. CDKs are also involved in the regulation of transcription and mRNA processing. CDKs phosphorylate proteins on serine and threonine amino acid residues: they are serine/threonine kinases. A cyclin-dependent kinase is activated by association with a cyclin, forming a cyclin-dependent kinase complex.
Olfactory receptors expressed in the cell membranes of olfactory receptor neurons are responsible for the detection of odor molecules. Activated olfactory receptors are the initial player in a signal transduction cascade which ultimately produces a nerve impulse which is transmitted to the brain. These receptors are members of the class A rhodopsin-like family of G protein-coupled receptors (GPCRs).
Nicotinic acetylcholine receptors, or nAChRs, are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons and on the postsynaptic side of the neuromuscular junction. Being ionotropic receptors, nAChRs are directly linked to an ion channel and do not make use of a second messenger as metabotropic receptors do.