A good example is the reaction between hydrogen and fluorine: H2 + F2 → 2HF We can write this overall reaction as two half-reactions: an oxidation reaction: H2 → 2H+ + 2e- and a reduction reaction: F2 + 2e- → 2F- Elements always have an oxidation number of zero. In the first half reaction hydrogen is oxidized from an oxidation number of zero to an oxidation number of +1. In the second half, reaction fluorine is reduced from an oxi ...

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Redox, Redox - Oxidizing and reducing agents, Redox - Oxidation in the industry, Redox - Former meaning oxygen/hydrogen, Redox - Examples of redox reactions, Redox - Other examples, Redox - Redox reactions in biology

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The outer and inner membranes of the mitochondria are composed of phospholipid bilayers studded with proteins, much like a typical cell membrane. The two membranes, however, have very different properties. The outer mitochondrial membrane, which encloses the entire organelle, is composed of about 50% phospholipids by weight and contains a variety of enzymes involved in such diverse activities such as the oxidation of epinephrine (adrenaline), the degradation of tryptophan, and the elongation of fatty acids. The outer mitochondrial membrane c ...

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Mitochondrion, Mitochondrion - Mitochondrion structure, Mitochondrion - The mitochondrial matrix, Mitochondrion - Mitochondrial functions, Mitochondrion - Energy conversion, Mitochondrion - Use in population genetic studies, Mitochondrion - Origin, Mitochondrion - Reference, Mitochondrion - Mitochondrial structure, Mitochondrion - Fiction

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Cytokines mediate many important physiological functions including growth, development, wound healing and immune response. They may affect local tissues (paracrine effects) or more distant ones (endocrine effects) (Clark, 2005). Cytokines act by binding to their cell-specific receptors. These receptors are located in the cell membrane, and each allows a distinct signal transduction cascade to start in the cell, that eventually will lead to biochemical and phenotypical changes in the target cell. Typically, receptors for ...

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Cytokine, Cytokine - Effects, Cytokine - Types, Cytokine - Characteristics, Cytokine - History, Cytokine - Links

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Eukaryotic cells include a variety of membrane-bound structures, collectively referred to as the endomembrane system. Simple compartments, called vesicles or vacuoles, can form by budding off other membranes. Many cells ingest food and other materials through a process of endocytosis, where the outer membrane invaginates and then pinches off to form a vesicle. It is probable that most other membrane-bound organ ...

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Eukaryote, Eukaryote - Structure, Eukaryote - Internal membranes, Eukaryote - Mitochondria and plastids, Eukaryote - Cytoskeletal structures, Eukaryote - Reproduction, Eukaryote - Origin and evolution

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By separating from the trophoblast, the epiblast forms a new cavity, the amniotic cavity. This is lined by the amnionic membrane, with cells that come from the epiblast (called amnioblasts). Some hypoblast cells migrate along the inner cytotrophoblast lining of the blastocoel, secreting an extracellular matrix along the way. These hypoblast cells and extracellular matrix are called Heuser's membrane (or exoceolomic membrane), and the blastocoel is now called ...

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Mammalian embryogenesis, Mammalian embryogenesis - From one cell to blastocyst, Mammalian embryogenesis - Blastocyst grows and invades, Mammalian embryogenesis - Inner cell mass differentiation, Mammalian embryogenesis - Cavity formation

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The resting membrane potential is the difference in ionic charge across the membrane of the cell during phase 4 of the action potential. The normal resting membrane potential in the ventricular myocardium is about -85 to -95 mV. This potential is determined by the selective permeability of the cell membrane to various ions. The resting membrane potential is permeable to K+, and is relatively impermeable to other ions. The resting membrane potential is therefore determined by the K+ gradient across the cell membrane (the ...

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Cardiac action potential, Cardiac action potential - Resting membrane potential, Cardiac action potential - Phases of the cardiac action potential, Cardiac action potential - Phase 4, Cardiac action potential - Phase 0, Cardiac action potential - Phase 1, Cardiac action potential - Phase 2, Cardiac action potential - Phase 3, Cardiac action potential - Abnormal automaticity

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In phosphoglycerides, the carboxyl group of each fatty acid is esterified to the hydroxyl groups on carbon-1 and carbon-2. The phosphate group is attached to carbon-3 by an ester link. This molecule, known as a phosphatidate, is present in small quantities in membranes, but is also a precursor for the other phosphoglycerides. Phospholipid - Phosphatidyl choline. Phosphatidyl choline is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons. See also:

Phospholipid, Phospholipid - Phosphoglycerides, Phospholipid - Phosphatidyl choline, Phospholipid - Phosphatidyl ethanolamine, Phospholipid - Phosphatidyl inositol, Phospholipid - Phosphatidyl serine, Phospholipid - Diphosphatidyl glycerol, Phospholipid - Synthesis, Phospholipid - Sphingomyelin, Phospholipid - Amphipathic character

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Sulfonylurea - Method of action. Sulfonylureas bind to an ATP-dependent K+ channel on the cell membrane of pancreatic beta cells. This inhibits a tonic, hyperpolarizing outflux of potassium, which causes the electric potential over the membrane to become more positive. This depolarization opens voltage-gated Ca2+ channels. The rise in intracellular calcium leads to increased fusion of insulin granulae with the cell membrane, and t ...

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Sulfonylurea, Sulfonylurea - Drugs in this class, Sulfonylurea - Chemistry, Sulfonylurea - Pharmacology, Sulfonylurea - Method of action, Sulfonylurea - Pharmacokinetics, Sulfonylurea - Uses, Sulfonylurea - Side-effects and cautions, Sulfonylurea - History

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In eukaryotes, Ca2+ ions are one of the most widespread second messengers used in signal transduction. They make their entrance into the cytoplasm either from outside the cell through the cell membrane via calcium channels (such as Ca-binding proteins), or from some internal calcium storages. Ca2+ entering the cell plasma causes the specific action of the cell, whatever this action is: secretory cells release vesicles with their secretion, muscle cells contract, synapses release synaptic vesicles ...

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Calcium in biology, Calcium in biology - Measuring Ca2+ in living tissue, Calcium in biology - Organs and tissues, Calcium in biology - Cell biology, Calcium in biology - Calcium in plants, Calcium in biology - Structural roles, Calcium in biology - Cell signalling, Calcium in biology - Food sources

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When certain proteins are synthesized by a ribosome, it can become "membrane-bound", associated with the membrane of the nucleus and the rough endoplasmic reticulum (in eukaryotes only) for the time of synthesis. They insert the freshly produced polypeptide chains directly into the ER, from where they are transported to their destinations. Bound ribosomes usually produce proteins that are used within the cell membrane ...

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Ribosome, Ribosome - Overview, Ribosome - Free ribosomes, Ribosome - Membrane bound ribosomes, Ribosome - Atomic structure, Ribosome - External link

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Calcium in biology - Structural roles. Ca2+ ions are an essential component of plant cell walls and cell membranes, and are used as cations to balance organic anions in the plant vacuole. The Ca2+ concentration of the vacuole may reach millimolar levels. The most striking use of Ca2+ ions as a structural element in plants occurs in the marine coccolithophores, which use Ca2+ to form the calcium carbonate plates with which they are covered.

Calcium in biology, Calcium in biology - Measuring Ca2+ in living tissue, Calcium in biology - Organs and tissues, Calcium in biology - Cell biology, Calcium in biology - Calcium in plants, Calcium in biology - Structural roles, Calcium in biology - Cell signalling, Calcium in biology - Food sources

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Gross examination shows a hypervascular lesion in the renal cortex, which is frequently multilobulated, yellow (because of the lipid accumulation) and calcified. Light microscopy shows tumor cells forming cords, papillae, tubules or nests, and are atypical, polygonal and large. Because these cells accumulate glycogen and lipids, their cytoplasm appear "clear", lipid-laden, the nuclei remain in the middle of the cells, and the cellular membrane is evident. Some cells may be smaller, with eosinophilic cytoplasm, resembling normal tubula ...

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Renal cell carcinoma, Renal cell carcinoma - Signs and symptoms, Renal cell carcinoma - Causes, Renal cell carcinoma - Pathology, Renal cell carcinoma - Radiology, Renal cell carcinoma - Treatment, Renal cell carcinoma - Surgery, Renal cell carcinoma - Percutaneous therapies, Renal cell carcinoma - Radiation therapy, Renal cell carcinoma - Medications, Renal cell carcinoma - Chemotherapy, Renal cell carcinoma - Prognosis, Renal cell carcinoma - External link

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The chloroplast has a two membrane envelope termed the Inner & Outer membrane respectively. Between these two layers is the Intermembrane space. The fluid within the chloroplast is called the stroma, corresponding to the cytoplasm of the bacterium, and contains tiny circular DNA and ribosomes, though most of their proteins are encoded by genes contained in the cell nucleus, with the protei ...

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Chloroplast, Chloroplast - Origins, Chloroplast - Structure, Chloroplast - Biochemistry

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The cell structure of prokaryotes differs greatly from eukaryotes in many ways. The defining characteristic is, of course, the absence of a nucleus or nuclear envelope. Prokaryotes also were previously considered to lack cytoskeletons and do lack membrane-bound cell compartments such as vacuoles, endoplasmic reticulum, mitochondria and chloroplasts. In eukaryotes, the latter two perform various metabolic processes and are believed to have been derived from endosymbiotic bacteria. In prokaryotes similar processes occur across the cell membran ...

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Prokaryote, Prokaryote - Structure, Prokaryote - Environment, Prokaryote - Evolution of prokaryotes

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The T-Virus is like any other virus. It is a protein crystal with a DNA core. As the crystal makes contact with a cell's membrane, it destroys it and inserts its DNA into the cell. The cell absorbs the viral genome into its own DNA, which takes over the cell's functions. The cell begins to produce offspring of the original virus. The new viruses are then released from the host cell and infect the neighboring ...

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T-Virus, T-Virus - History, T-Virus - Effects of Infection, T-Virus - The Movies, T-Virus - Means of Infection, T-Virus - Known Antigens, T-Virus - Trivia

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Ketoconazole is structurally similar to imidazole, and interferes with the fungal synthesis of ergosterol, the main constituent of cell membranes, as well as certain enzymes. It is specific for fungi, as mammalian cell membranes contain no ergosterol. As with all azole antifungal agents, ketoconazole works principally by inhibition of an enzyme, cytochrome P450 14-alpha-demethylase (P45014DM). This enzyme is in the sterol biosynthesis pathway that leads from lanosterol to ergosterol. Fluconazole and itraconazole have been found to have a greater affinity for fungal cell membrane than ketoconazole, and thus lower ...

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Ketoconazole, Ketoconazole - History, Ketoconazole - Usage, Ketoconazole - Method of action, Ketoconazole - Sensitive fungi

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In trophoblast cells which eventually form the placenta, and inner cell mass (also called embryoblast) of undifferentiated cells which are a source of embryonic stem cells. The blastocyst can be thought of as a ball of a (mostly single) layer of trophoblast cells, with inner cell mass attached to this ball's inner wall. The embryo plus its membranes is called the conceptus. By this stage the conceptus is in the uterus. The zona pellucida ultimately disappears. The trophoblast then differentiates into two distinct layers: the inner is the cytotrophoblast consisting of cuboidal cells that are ...

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Mammalian embryogenesis, Mammalian embryogenesis - From one cell to blastocyst, Mammalian embryogenesis - Blastocyst grows and invades, Mammalian embryogenesis - Inner cell mass differentiation, Mammalian embryogenesis - Cavity formation

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With respect to a cell, organelle, or other subcellular compartment, the propensity of an electrically charged solute, such as a potassium ion, to move across the membrane is decided by the difference in its electrochemical potential on either side of the membrane, which arises from three factors: the difference in the concentration of the solute between the two sides of the membrane the charge or "valence" of the solute molecule the difference in voltage between the two sides ...

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Electrochemical gradient, Electrochemical gradient - General overview, Electrochemical gradient - Chemistry, Electrochemical gradient - Biological context, Electrochemical gradient - Ion gradients, Electrochemical gradient - Proton gradients

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1. During the undershoot period after an action potential, the membrane potential is more negative than when the cell is in the "resting state". In the figure to the right, this undershoot is from approximately 3 to 4 milliseconds (ms) on the graph. The undershoot is the time when the membrane potential is hyperpolarized relative to the resting potential. 2. During the rising phase of an action potential, the membrane potential changes from negative to positive. In the figure, the rising phase is from approximately 1 to 2 milli ...

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Hyperpolarization biology, Hyperpolarization biology - Examples, Hyperpolarization biology - Vernacular usage, Hyperpolarization biology - Related topics

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With respect to a cell, organelle, or other subcellular compartments, the inclined tendency of an electrically charged solute, such as a potassium ion, to move across the membrane is decided by the difference in it's electrochemical potential on either side of the membrane, which arises from three factors: the difference in the concentration of the solute between the two sides of the membrane the charge or "valence" of the solute molecule the difference in voltage between the two sides ...

See also:

Electrochemical gradient, Electrochemical gradient - General overview, Electrochemical gradient - Chemistry, Electrochemical gradient - Biological context, Electrochemical gradient - Ion gradients, Electrochemical gradient - Proton gradients

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Skin is composed of the epidermis and the dermis. Below these layers lies the hypodermis, which is not usually classified as a layer of skin. The outermost epidermis is made up of stratified squamous epithelium with an underlying basement membrane. It contains no blood vessels, and is nourished by diffusion from the dermis. The main type of cells which make up the epidermis are keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strataSee also:

Skin, Skin - Layers, Skin - Types, Skin - Functions, Skin - Hygiene, Skin - Aging and disease

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An electrical voltage, or potential, always exists between the inside and outside of a cell. The voltage of an inactive cell stays at a negative value (inside relative to outside the cell) and varies within a small range. When the membrane potential of an excitable cell is depolarized beyond a threshold, the cell will undergo (or "fire") an action potential (see Threshold and initiation). At its most basic, an action potential is a very rapid swing in the polarity of the membrane potential from negative to positive and back, th ...

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Action potential, Action potential - Overview, Action potential - Underlying mechanism, Action potential - Resting membrane potential, Action potential - Action potential phases, Action potential - Threshold and initiation, Action potential - Circuit model, Action potential - Propagation, Action potential - Speed of propagation, Action potential - Saltatory conduction, Action potential - Refractory period, Action potential - Why an action potential?

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