|
Exocytosis
Exocytosis is a term for the active transport process that transports large molecules from cell to the extracellular area. Hormones, proteins and neurotransmitters are examples of large molecules that can be transported out of the cell. Exocytosis is a crucial transport mechanism that enables polar molecules to flow through the cell membranes’ hydrophobic lipid bilayer. The transport process is essential to hormone secretion, immune response and neurotransmission. Both prokaryotes and eukaryotes undergo exocytosis. Prokaryotes secrete molecules and cellular waste through translocons that are localized to the cell membrane. In addition, they secrete molecules to other cells through specialized organs. Eukaryotes rely on multiple cellular processes to perform the exocytosis process. Eukaryotes have several organelles and a nucleus in the cytoplasm that are connected through multiple transport routes, that is formally known as the secretory pathway. This is a complex pathway with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SNARE Protein
SNARE proteins – " SNAP REceptors" – are a large protein family consisting of at least 24 members in yeasts and more than 60 members in mammalian and plant cells. The primary role of SNARE proteins is to mediate the fusion of vesicles with the target membrane; this notably mediates exocytosis, but can also mediate the fusion of vesicles with membrane-bound compartments (such as a lysosome). The best studied SNAREs are those that mediate the release of synaptic vesicles containing neurotransmitters in neurons. These neuronal SNAREs are the targets of the neurotoxins responsible for botulism and tetanus produced by certain bacteria. Types SNAREs can be divided into two categories: ''vesicle'' or ''v-SNAREs'', which are incorporated into the membranes of transport vesicles during budding, and ''target'' or ''t-SNAREs'', which are associated with nerve terminal membranes. Evidence suggests that t-SNAREs form stable subcomplexes which serve as guides for v-SNARE, incorpo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SNAP25
Synaptosomal-Associated Protein, 25kDa (SNAP-25) is a Target Soluble NSF (''N''-ethylmaleimide-sensitive factor) Attachment Protein Receptor ( t-SNARE) protein encoded by the ''SNAP25'' gene found on chromosome 20p12.2 in humans. SNAP-25 is a component of the ''trans''-SNARE complex, which accounts for membrane fusion specificity and directly executes fusion by forming a tight complex that brings the synaptic vesicle and plasma membranes together. Structure and function SNAP-25, a Q-SNARE protein, is anchored to the cytosolic face of membranes via palmitoyl side chains covalently bound to cysteine amino acid residues in the central linker domain of the molecule. This means that SNAP-25 does not contain a trans-membrane domain. SNAP-25 has been identified to contribute two α-helices to the SNARE complex, a four-α-helix domain complex. The SNARE complex participates in vesicle fusion, which involves the docking, priming and merging of a vesicle with the cell membrane to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exocyst
The exocyst is an octameric protein complex involved in vesicle trafficking, specifically the tethering and spatial targeting of post- Golgi vesicles to the plasma membrane prior to vesicle fusion. It is implicated in a number of cell processes, including exocytosis, cell migration, and growth. Subunits The exocyst is composed of eight subunits, whose nomenclature differs between mammalian cells and ''Saccharomyces cerevisiae''. Function The exocyst complex serves to direct vesicles after the Golgi complex to specific locations on the plasma membrane and to mediate their tethering and localization to the membrane immediately before fusion. The exocyst complex has also been implicated in the active trafficking of mitochondria from immune cells to cancer cells. Because of this function, the exocyst complex is heavily involved in exocytosis. Sec3 (EXOC1) and Exo70 (EXOC7) are localized to the plasma membrane, and are physically attached to the membrane by Rho GTPases such as CD ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syntaxin
Syntaxins are a family of membrane integrated Q-SNARE proteins participating in exocytosis. Domains Syntaxins possess a single C-terminal transmembrane domain, a SNARE domain (known as H3), and an N-terminal regulatory domain (Habc). Syntaxin 17 may have two transmembrane domains. * The SNARE (H3) domain binds to both synaptobrevin and SNAP-25 forming the core SNARE complex. Formation of this stable SNARE core complex is believed to generate the free energy required to initiate fusion between the vesicle membrane and plasma membrane. * The N-terminal Habc domain is formed by 3 α-helices and when collapsed onto its own H3 helix forms an inactive "closed" syntaxin conformation. This closed conformation of syntaxin is believed to be stabilized by binding of Munc-18 (nSec1), although more recent data suggests that nSec1 may bind to other conformations of syntaxin, as well. The "open" syntaxin conformation is the conformation that is competent to form into SNARE core complex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurotransmission
Neurotransmission (Latin: ''transmissio'' "passage, crossing" from ''transmittere'' "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron), and bind to and react with the receptors on the dendrites of another neuron (the postsynaptic neuron) a short distance away. Changes in the concentration of ions, such as Ca2+, Na+, K+, underlie both chemical and electrical activity in the process. The increase in calcium levels is essential and can be promoted by protons. A similar process occurs in retrograde neurotransmission, where the dendrites of the postsynaptic neuron release retrograde neurotransmitters (e.g., endocannabinoids; synthesized in response to a rise in intracellular calcium levels) that signal through receptors that are located on the axon terminal of the presynaptic neuron, mainly at GABAergic and glutamatergic synapses. Neurotransmission is regulated by severa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microfilament
Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin, but are modified by and interact with numerous other proteins in the cell. Microfilaments are usually about 7 nm in diameter and made up of two strands of actin. Microfilament functions include cytokinesis, amoeboid movement, cell motility, changes in cell shape, endocytosis and exocytosis, cell contractility, and mechanical stability. Microfilaments are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton tensile forces. In inducing cell motility, one end of the actin filament elongates while the other end contracts, presumably by myosin II molecular motors. Additionally, they function as part of actomyosin-driven contractile molecular motors, wherein the thin filaments serve as tensile platforms for myosin's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Transport
In cellular biology, active transport is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellular energy to achieve this movement. There are two types of active transport: primary active transport that uses adenosine triphosphate (ATP), and secondary active transport that uses an electrochemical gradient. This process is in contrast to passive transport, which allows molecules or ions to move down their concentration gradient, from an area of high concentration to an area of low concentration, with energy. Active transport is essential for various physiological processes, such as nutrient uptake, hormone secretion, and nig impulse transmission. For example, the sodium-potassium pump uses ATP to pump sodium ions out of the cell and potassium ions into the cell, maintaining a concentration gradient essential for cellular function. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Immune System
The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic worms, and also objects such as wood splinters, distinguishing them from the organism's own healthy biological tissue, tissue. Many species have two major subsystems of the immune system. The innate immune system provides a preconfigured response to broad groups of situations and stimuli. The adaptive immune system provides a tailored response to each stimulus by learning to recognize molecules it has previously encountered. Both use humoral immunity, molecules and cell-mediated immunity, cells to perform their functions. Nearly all organisms have some kind of immune system. Bacteria have a rudimentary immune system in the form of enzymes that protect against bacteriophage, viral infections. Other basic immune mechanisms evolved in ancien ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they are able to interact with neurotransmitter receptors on the target cell. Some neurotransmitters are also stored in large dense core vesicles. The neurotransmitter's effect on the target cell is determined by the receptor it binds to. Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available and often require a small number of biosynthetic steps for conversion. Neurotransmitters are essential to the function of complex neural systems. The exact number of unique neurotransmitters in humans is unknown, but more than 100 have been identified. Common neurotransmitters include Glutamate (neurotransmi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vesicle (biology And Chemistry)
In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form naturally during the processes of secretion ( exocytosis), uptake (endocytosis), and the transport of materials within the plasma membrane. Alternatively, they may be prepared artificially, in which case they are called liposomes (not to be confused with lysosomes). If there is only one phospholipid bilayer, the vesicles are called ''unilamellar liposomes''; otherwise they are called ''multilamellar liposomes''. The membrane enclosing the vesicle is also a lamellar phase, similar to that of the plasma membrane, and intracellular vesicles can fuse with the plasma membrane to release their contents outside the cell. Vesicles can also fuse with other organelles within the cell. A vesicle released from the cell is known as an extracellular vesicle. Vesicles perform a variety of functions. Because it is separated from the cytosol, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outer Membrane Vesicle
Outer membrane vesicles (OMVs) are vesicles released from the outer membranes of Gram-negative bacteria. While Gram-positive bacteria release vesicles as well, those vesicles fall under the broader category of bacterial membrane vesicles (MVs). OMVs were the first MVs to be discovered, and are distinguished from outer inner membrane vesicles (OIMVs), which are gram-negative bacterial vesicles containing portions of both the outer and inner bacterial membrane. Outer membrane vesicles were first discovered and characterized using transmission-electron microscopy by Indian Scientist Prof. Smriti Narayan Chatterjee and J. Das in 1966-67. OMVs are ascribed the functionality to provide a manner to communicate among themselves, with other microorganisms in their environment and with the host. These vesicles are involved in trafficking bacterial cell signaling biochemicals, which may include DNA, RNA, proteins, endotoxins and allied virulence molecules. This communication happens in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenosine Triphosphate
Adenosine triphosphate (ATP) is a nucleoside triphosphate that provides energy to drive and support many processes in living cell (biology), cells, such as muscle contraction, nerve impulse propagation, and chemical synthesis. Found in all known forms of life, it is often referred to as the "molecular unit of currency" for intracellular energy transfer. When consumed in a Metabolism, metabolic process, ATP converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP). Other processes regenerate ATP. It is also a Precursor (chemistry), precursor to DNA and RNA, and is used as a coenzyme. An average adult human processes around 50 kilograms (about 100 mole (unit), moles) daily. From the perspective of biochemistry, ATP is classified as a nucleoside triphosphate, which indicates that it consists of three components: a nitrogenous base (adenine), the sugar ribose, and the Polyphosphate, triphosphate. Structure ATP consists of three parts: a sugar, an amine base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.png "Click for more on -> Outer Membrane Vesicle")
