Biology questions and answers E

Biology E

What is ecdysone ?

A juvenile steroid hormone that affects arthropods and that belongs to the larger class of ecdysteroids, sterol derivatives that as a whole affect a variety of conditions relating to molting and metamorphosis, including eliciting molting, regulating growth of motor neurons, controlling choriogenesis, stimulating growth and development of imaginal discs, initiating breakdown of larval structures during metamorphosis, and eliciting the deposition of cuticle by the epidermis. In insects, ecdysone primarily elicits and stimulates molting. It acts on specific genes, stimulating the synthesis of proteins involved in these bodily changes, and is produced by prothoracic glands in insects and Y-organs (a gland near the external adductor muscles) in crustaceans. Ecdysone—formerly called alpha ecdysone, and beta ecdysone, or ecdysterone (now called 20-hydroxyecdysone [20-HE])—is believed to be the active form. Ecdysone is not the active molting hormone. Various tissues, including the fat body, convert ecdysone to 20hydroxyecdysone, the active form of molting hormone.

What is echinoderm ?

Diversified marine animals (phylum Echinodermata) that include the classes Crinoidea (sea lilies), Asteroidea (starfish), Ophiuroidea (brittle stars or snake stars), Echinoidea (sea urchins and sand dollars), and Holothuroidea (sea cucumbers).

What is echolocation ?

A form of sensory perception used by animals like bats to orient themselves in flight, detect objects, seek food, and communicate. Bats, for example, send out a series of short, high-pitched sounds, called echoes, that travel, hit an object, and bounce back, giving the bat the ability to judge distance, size, shape, and motion.

What is eclosion ?

The emergence of an adult insect from the pupa case or, less commonly, the hatching of an egg.

What is EC nomenclature for enzymes ?

A classification of ENZYMEs according to the Enzyme Commission of the International Union of Biochemistry and Molecular Biology. Enzymes are allocated four numbers, the first of which defines the type of reaction catalyzed; the next two define the SUBSTRATES; and the fourth is a catalog number. Categories of enzymes are EC 1, OXIDOREDUCTASEs; EC 2, TRANSFERASEs; EC 3, HYDROLASEs; EC 4, LYASEs; EC 5, ISOMERASEs; EC 6, LIGASEs (synthetases).

What is ecological efficiency ?

Each transfer of energy from one trophic level to another has an ecological efficiency associated with it. Ecological efficiency refers to the transfer of energy up trophic levels; it is the ratio of secondary productivity to primary productivity consumed.

Ecological efficiency goes down as you move up the trophic levels. Ecological efficiencies generally range from 5 to 20 percent, meaning that this percentage of primary-producer biomass consumed is converted into new consumer biomass.

Ecological efficiency depends on assimilation efficiency (that portion of the consumed energy assimilated) and on net production efficacy (that portion of the consumed energy converted into biomass). Assimilation efficiencies are greater for carnivores (50–90 percent) than for herbivores (20–60 percent).

What is ecological niche ?

The totality of biotic and abiotic resources an organism interacts with while living in its environment.

What is ecological succession ?

A transitional change in the biological community, where a group of plant and/or animal species gives way to another set of species over time, in response to a sequence of events such as fire, storms, human activities, or other natural or humanmade occurrences. The term also refers to the normal evolution of a community from pioneer stage to climax community when equilibrium between species and its environment occurs.

What is ecology ?

The study of all life forms and their interactions with their environment.

What is ecosystem ?

Any natural system—including biotic and abiotic parts—that interacts as a unit to produce a stable functioning system through cyclical exchange of materials.

What is ectoderm ?

The outer layer of an embryo’s three primary germ layers (endoderm, mesoderm, ectoderm) that gives rise to the nervous system and epidermis in vertebrates.

ectoparasite

A parasite that feeds from the exterior of its host.

What is ectotherm ?

A cold-blooded organism that relies on obtaining its heat from certain behavior techniques and from the external environment (sun); e.g., snakes, alligators, lizards, fish, or amphibians.

What is effector cell ?

A cell that performs a specific function in response to a stimulus. A gland or muscle cell that responds to stimuli from the body. Cells with full immune functions capable of participating in the immune response by destroying foreign cells or tissues; effector lymphocytes can mediate the removal of pathogens from the body.

What is efficacy ?

Describes the relative intensity with which AGONISTs vary in the response they produce, even when they occupy the same number of RECEPTORs and with the same AFFINITY. Efficacy is not synonymous with INTRINSIC ACTIVITY.

Efficacy is the property that enables DRUGs to produce responses. It is convenient to differentiate the properties of drugs into two groups: those that cause them to associate with the receptors (affinity) and those that produce stimulus (efficacy). This term is often used to characterize the level of maximal responses induced by agonists. In fact, not all agonists of a receptor are capable of inducing identical levels of maximal response. Maximal response depends on the efficiency of receptor coupling, i.e., from the cascade of events that, from the binding of the drug to the receptor, leads to the observed biological effect.

What is EF-hand ?

A common structure to bind Ca2+ in CALMODULIN and other Ca2+-binding proteins consisting of a HELIX (E), a loop, and another helix (F).

Who was Ehrlich, Paul ?

Ehrlich, Paul (1854–1915) German/Polish Immunologist Paul Ehrlich was born on March 14, 1854, near Breslau, Germany (now Wroclaw, Poland), to Ismar Ehrlich and his wife Rosa Weigert, whose nephew was the great bacteriologist Karl Weigert.

Ehrlich was educated at the Breslau Gymnasium and then at the Universities of Breslau, Strassburg, Freiburg-im-Breisgau, and Leipzig. He received his doctorate in medicine in 1878 for his dissertation on the theory and practice of staining animal tissues based on the work of aniline dyes discovered by W. H. Perkin in 1853

In 1878 Ehrlich was appointed assistant professor at the Berlin Medical Clinic, where he continued his work with dyes used for staining tissues, classifying them as being basic, acid, or neutral. His work on staining granules in blood cells laid the foundation for future work on hematology (the study of blood and blood-forming tissues) and in the field of staining of tissues.

In 1882 Ehrlich published his method of staining the tubercle bacillus that Robert Koch had discovered, and it was this technique that later became the precursor for the currently used Gram method of staining bacteria. Ehrlich himself had a bout of tuberculosis. Ehrlich also discovered the blood–brain barrier when he noticed that the dyes injected into an animal brain would not stain.

In 1899 he became director of the newly created Royal Institute of Experimental Therapy in Frankfurt and of the Georg-Speyer Haus, founded by Frau Franziska Speyer for chemotherapy studies, which was built next door to Ehrlich’s institute. It is here that he began work on serum antitoxins and chemotherapy and came up with the concept of the “magic bullet,” a compound that could be made to selectively target a disease-causing organism, killing only that organism. His research programs were guided by his theory that the germicidal capability of a molecule depended on its structure, especially its side chains, which could bind to the disease-causing organism. After many trials searching hundreds of agents with the help of the nearby Cassella chemical works, which donated samples of new compounds produced in their laboratory, in 1909 he found a cure for syphilis. The agent he identified was arsphenamine, trade name Salvarsan (the 606th substance tested) and later Neosalvaran (the 914th substance tested). Ehrlich became one of the founders of chemotherapy.

Ehrlich received the Tiedemann Prize of the Senckenberg Naturforschende Gesellschaft at Frankfurt/Main in 1887, the Prize of Honor at the XVth International Congress of Medicine at Lisbon in 1906, the Liebig Medal of the German Chemical Society in 1911, and in 1914 the Cameron Prize of Edinburgh. In 1908 he shared, with Ilya Ilyich Mechnikov, the Nobel Prize in recognition for his work on immunity.

The Prussian government elected him privy medical counsel in 1897, to a higher rank of the counsel in 1907, and in 1911 he reached the highest rank possible, real privy counsel with the title of excellency. He died on August 20, 1915, from a stroke.

Who was Eijkman, Christiaan ?

Eijkman, Christiaan (1858–1930) Dutch Physician Christiaan Eijkman was born on August 11, 1858, at Nijkerk in Gelderland (The Netherlands) to Christiaan Eijkman, the headmaster of a local school, and Johanna Alida Pool. He received his education at his father’s school in Zaandam. In 1875 he entered the Military Medical School of the University of Amsterdam and received training as a medical officer for the Netherlands Indies Army. From 1879 to 1881 he wrote his thesis “On Polarization of the Nerves,” which gained him his doctor’s degree, with honors, on July 13, 1883. On a trip to the Indies he caught malaria and returned to Europe in 1885.

Eijkman was director of the Geneeskundig Laboratorium (medical laboratory) in Batavia from 1888 to 1896, and during that time he made a number of important researches in nutritional science. In 1893 he discovered that the cause of beriberi was a deficiency of vitamins and not, as thought by the scientific community, of bacterial origin. He discovered vitamin B, and this discovery led to the whole concept of vitamins. For this discovery he was awarded the Nobel Prize in physiology or medicine for 1929.

He wrote two textbooks for his students at the Java Medical School, one on physiology and the other on organic chemistry.

In 1898 he became a professor of hygiene and forensic medicine at Utrecht, but he also engaged in problems of water supply, housing, school hygiene, and physical education. As a member of the Gezondheidsraad (health council) and the Gezondheids Commissie (health commission), he participated in the struggle against alcoholism and tuberculosis. He was also the founder of the Vereeniging tot Bestrijding van de Tuberculose (Society for the struggle against tuberculosis). Eijkman died in Utrecht on November 5, 1930.

Eijkman’s syndrome, a complex of nervous symptoms in animals deprived of vitamin B1, is named for him.

Who was Einthoven, Willem ?

Einthoven, Willem (1860–1927) Dutch Physiologist Willem Einthoven was born on May 21, 1860, in Semarang on the island of Java, Indonesia, to Jacob Einthoven, an army medical officer in the Indies, and Louise M. M. C. de Vogel, daughter of the thendirector of finance in the Indies.

Upon the death of his father, Einthoven and his family moved to Holland and settled in Utrecht, where he attended school. In 1878 he entered the University of Utrecht as a medical student. In 1885, after receiving his medical doctorate, he was appointed successor to A. Heynsius, professor of physiology at the University of Leiden, where he stayed until his death.

He conducted a great deal of research on the heart. To measure the electric currents created by the heart, he invented a string galvanometer (called the Einthoven galvanometer) and was able to measure the changes of electrical potential caused by contractions of the heart muscle and to record them by creating the electrocardiograph (EKG), a word he coined. The EKG provides a graphic record of the action of the heart. This work earned him the Nobel Prize in physiology or medicine for 1924. He published many scientific papers in journals of the time. He died on September 29, 1927.

What is electrochemical gradient ?

The relative concentration of charged ions across a membrane. Ions move across the membrane due to the concentration difference on the two sides of the membrane as well as the difference in electrical charge across the membrane.

What is electrode potential ?

Electrode potential of an electrode is defined as the electromotive force (emf) of a cell in which the electrode on the left is a standard hydrogen electrode and the electrode on the right is the electrode in question.

What is electrogenic pump ?

Any large, integral membrane protein (pump) that mediates the movement of a sub stance (ions or molecules) across the plasma membrane against its energy gradient (active transport). The pump, which can be ATP-dependent or Na+-dependent, moves net electrical charges across the membrane.

What is electromagnetic spectrum ?

The entire spectrum of radiation arranged according to frequency and wavelength that includes visible light, radio waves, microwaves, infrared, ultraviolet light, X rays, and gamma rays. Wavelengths range from less than a nanometer, i.e., X and gamma rays (1 nanometer is about the length of 10 atoms in a row), to more than a kilometer, i.e., radio waves. Wavelength is directly related to the amount of energy the waves carry. The shorter the radiation’s wavelength, the higher its energy. Frequencies of the electromagnetic spectrum range from high (gamma rays) to low (AM radio). All electromagnetic radiation travels through space at the speed of light, or 186,000 miles (300,000 km) per second.

What is electron ?

A negatively charged subatomic particle of an atom or ion.

What is electron acceptor ?

A substance that receives electrons in an oxidation-reduction reaction.

What is electronegativity ?

Each kind of atom has a certain attraction for the electrons involved in a chemical bond. This attraction can be listed numerically on a scale of electronegativity. Since the element fluorine has the greatest attraction for electrons in bondforming, it has the highest value on the scale. Metals usually have a low electronegativity, while nonmetals usually have high electronegativity. When atoms react with one another, the atom with the higher electronegativity value will always pull the electrons away from the atom that has the lower electronegativity value.

What is electron microscope (EM) ?

A very large tubular microscope that focuses a highly energetic electron beam instead of light through a specimen, resulting in a resolving power thousands of times greater than that of a regular light microscope. A transmission EM (TEM) is used to study the internal structure of thin sections of cells, while a scanning EM (SEM) is used to study the ultrastructure of surfaces. The transmission electron microscope, the first type of electron microscope, was developed in 1931 by Max Knoll and Ernst Ruska in Germany and was patterned exactly on the light transmission microscope except that it used a focused beam of electrons instead of light to see through the specimen. The first scanning electron microscope was built in 1942, but it was not available commercially until 1965.

What is electron-nuclear double resonance (ENDOR) ?

A magnetic resonance spectroscopic technique for the determination of HYPERFINE interactions between electrons and nuclear spins. There are two principal techniques. In continuous-wave ENDOR, the intensity of an ELECTRON PARAMAGNETIC RESONANCE signal, partially saturated with microwave power, is measured as radio frequency is applied. In pulsed ENDOR the radio frequency is applied as pulses and the EPR signal is detected as a spin-echo. In each case an enhancement of the EPR signal is observed when the radio frequency is in resonance with the coupled nuclei.

What is electron paramagnetic resonance (EPR) ?

electron paramagnetic resonance (EPR) spectroscopy The form of spectroscopy concerned with microwave-induced transitions between magnetic energy levels of electrons having a net spin and orbital angular momentum. The spectrum is normally obtained by magnetic-field scanning. Also known as electron spinresonance (ESR) spectroscopy or electron magnetic resonance (EMR) spectroscopy. The frequency (ν) of the oscillating magnetic field to induce transitions between the magnetic energy levels of electrons is measured in gigahertz (GHz) or megahertz (MHz). The following band designations are used: L (1.1 GHz), S (3.0 GHz) , X (9.5 GHz), K (22.0 GHz), and Q (35.0 GHz). The static magnetic field at which the EPR spectrometer operates is measured by the magnetic flux density (B), and its recommended unit is the tesla (T). In the absence of nuclear hyperfine interactions, B and ν are related by: h ν = gµBB, where h is the Planck constant, µB is the Bohr magneton, and the dimensionless scalar g is called the g-factor. When the paramagnetic species exhibits an ANISOTROPY, the spatial dependency of the g-factor is represented by a 3 × 3 matrix. The interaction energy between the electron spin and a magnetic nucleus is characterized by the hyperfine coupling constant A. When the paramagnetic species has anisotropy, the hyperfine coupling is expressed by a 3 × 3 matrix called a hyperfine-coupling matrix. Hyperfine interaction usually results in splitting of lines in an EPR spectrum. The nuclear species giving rise to the hyperfine interaction should be explicitly stated, e.g., “the hyperfine splitting due to 65Cu.” When additional hyperfine splittings due to other nuclear species are resolved (“superhyperfine”), the nomenclature should include the designation of the nucleus and the isotope number.

What is electron spin-echo (ESE) ?

electron spin-echo (ESE) spectroscopy A pulsed technique in ELECTRON PARAMAGNETIC RESONANCE, in some ways analogous to pulsed techniques in NMR (NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY). ESE can be used for measurements of electron spin relaxation times, as they are influenced by neighboring paramagnets or molecular motion. It can also be used to measure anisotropic nuclear hyperfine couplings. The effect is known as electron spin-echo envelope modulation (ESEEM). The intensity of the electron spin-echo resulting from the application of two or more microwave pulses is measured as a function of the temporal spacing between the pulses. The echo intensity is modulated as a result of interactions with the nuclear spins. The frequency-domain spectrum corresponds to hyperfine transition frequencies.

What is electron-transfer protein ?

A protein, often containing a metal ion, that oxidizes and reduces other molecules by means of electron transfer.

What is electron-transport chain ?

A chain of electron acceptors embedded in the inner membrane of the mitochondrion. These acceptors separate hydrogen protons from their electrons. When electrons enter the transport chain, the electrons lose their energy, and some of it is used to pump protons across the inner membrane of the mitochondria, creating an electrochemical gradient across the inner membrane that provides the energy needed for ATP (adenosine triphosphate) synthesis. The function of this chain is to permit the controlled release of free energy to drive the synthesis of ATP.

What is element ?

A substance consisting of atoms that have the same number of protons in their nuclei. Elements are defined by the number of protons they possess.

What is elephantiasis (lymphedema filariasis) ?

A visibly grotesque enlargement and hardening of the skin and subcutaneous tissues, usually in the leg or region of the testis, caused by obstruction of the lymphatic system when the lymph node is infested by the nematode worm, Wuchereria bancrofti.

What is elimination ?

The process achieving the reduction of the concentration of a XENOBIOTIC compound, including its reduction via METABOLISM.

What is embryo ?

The resulting organism that grows from a fertilized egg following rapid development and eventually becomes an offspring (in humans, a baby). In plants, it is the undeveloped plant contained within a seed.

What is embryo sac ?

A large cell that develops in the ovule of flowering plants (angiosperms). It contains the egg cell, the female gametophyte, where pollination occurs, and when fertilized it becomes an embryo and eventually a seed. It is formed from the growth and division of the megaspore into a multicellular structure with eight haploid nuclei.

What is emigration ?

The process of an individual or group leaving a population.

What is emulsion ?

Droplets of a liquid substance dispersed in another immiscible liquid. Milk in salad dressing is an emulsion.

What is enantiomer ?

One of a pair of molecular entities that are mirror images of each other and nonsuperimposable

What is endangered species ?

The classification provided to an animal or plant in danger of extinction within the foreseeable future throughout all or a significant portion of its range.

What is Endangered Species Act of 1973 ?

Federal legislation in the United States intended to provide a means whereby the ecosystems upon which endangered and threatened species depend may be conserved, and to provide programs for the conservation of those species in the hope of preventing extinction of native plants and animals.

What is endemic species ?

A species native and confined to a certain region; a species having comparatively restricted distribution.

What is endergonic reaction ?

A chemical reaction that consumes energy rather than releases energy. Endergonic reactions are not spontaneous because they do not release energy.

Who was Enders, John Franklin ?

Enders, John Franklin (1897–1985) American Virologist John Franklin Enders was born on February 10, 1897, at West Hartford, Connecticut, to John Ostrom Enders, a banker in Hartford, and Harriet Goulden Enders (née Whitmore). He was educated at the Noah Webster School at Hartford and St. Paul’s School in Concord, New Hampshire. In 1915 he went to Yale University, left to become an air force pilot in 1918, and returned to get his B.A. in 1920. He received a Ph.D. at Harvard in 1930 for a thesis that presented evidence that bacterial anaphylaxis and hypersensitivity of the tuberculin type are distinct phenomena, and he stayed at Harvard until 1946 as a teacher.

In 1938 Enders began the study of some of the mammalian viruses and undertook, in 1941, in collaboration with others, a study of the virus of mumps. This work provided serological tests for the diagnosis of this disease and a skin test for susceptibility to it. It also demonstrated the immunizing effect of inactivated mumps virus and the possibility of attenuating the virulence of this virus by passing it through chick embryos. It showed that mumps often occurs in a form that is not apparent but that nevertheless confers a resistance that is as effective as that conferred by the visible disease.

In 1946 Enders established a laboratory for research in infectious diseases at the Children’s Medical Center at Boston. The understanding of viruses at the time was scant, and development of an antipolio vaccine depended on gaining the ability to grow sufficient quantities of the polio virus under laboratory control. The stumbling block was that poliovirus cultures could be kept alive for a useful length of time only in nerve tissue, and that was hard to obtain and maintain.

Enders, along with T. H. WELLER and F. C. ROBBINS, found that viruses could be grown on tissues treated with penicillin to retard bacterial growth, and they were also successful in growing mumps and polio viruses as well. The ability to grow and study polio led to the development of a vaccine later by Salk and Sabin. The research opened the way to other vaccines against highly contagious childhood diseases such as measles, German measles (rubella), and mumps. Enders, Robbins, and Weller shared the 1954 Nobel Prize in medicine for this pioneering work.

Enders was a member of many organizations. Considered one of the most important contributors of the 20th century, Enders also provided insight to links between viruses and cancer, and the pattern and process of tumor growth. He died on September 8, 1985.

What is endocrine gland ?

A ductless organ that produces and secretes hormones into the bloodstream.

What is endocrine system ?

A collection of glands that work interdependently and produce hormones that regulate the body’s growth, metabolism, and sexual development and function. The endocrine system consists of: two adrenal glands, located on the top of each kidney; the pancreas, found in the abdominal cavity behind the stomach; the parathyroid and thyroid, located at the base of the neck; the pituitary, located at the base of the brain; and the ovaries and testes, the female and male sex glands.

Each of the endocrine glands produces hormones that are targeted to a particular area of the body and are released into the bloodstream and serve to regulate the activity of various organs, tissues, and body functions.

What is endocytosis ?

A process by which liquids or solid particles are taken up by a cell through invagination of the plasma membrane. The plasma membrane creates a “well” in which the substances settle, become surrounded, and are then pinched off into a vesicle that can be transported through the cell.

What is endoderm ?

One of three primary germ layers in embryonic development (along with mesoderm and ectoderm). The endoderm is the inner layer of cells and gives rise to organs and tissues associated with digestion and respiration.

What is endodermis ?

A parenchyma tissue that regulates the transport of materials into the vascular bundles of most roots, stems, and leaves. It surrounds the vascular cylinder; is especially prominent in roots; and has suberized Casparian strips, a band of suberin (waxy substance) within the anticlinal walls. It is the innermost layer of the cortex in plant roots.

What is endogenous ?

Originating internally. In the description of metal ion COORDINATION in metalloproteins, endogenous refers to internal, or protein-derived, LIGANDs

What is endomembrane system ?

The collection or network of membranous organelles, such as the endoplasmic reticulum and the Golgi apparatus, that are inside a eukaryotic cell; divides the cytoplasm into compartments with various functions, with the compartments related via direct physical contact or by the use of membranous vesicles.

What is endometrium ?

The lining (mucous membrane) of the uterus and cervix. The endometrium becomes thicker as the menstrual cycle advances in preparation for a fertilized egg. If fertilization does not occur, the endometrium is shed with the menstrual flow. It consists of the stratum functionale, a thick part of endometrium that is lost during menstruation, and the stratum basal, a layer retained during menstruation that serves as a stem source for regeneration of the upper stratum functionale.

A cancerous growth in the endometrium is called endometrial cancer, and an overgrowth in the endometrium, called endometrial hyperplasia, can cause abnormal menstrual bleeding and become precancerous.

What is endoparasite ?

Any parasitic organism that lives and feeds from inside its host.

What is endoplasmic reticulum (ER) ?

An extensive convoluted membranous network in the cytoplasm of eukaryotic cells containing two types. The first is a rough endoplasmic reticulum, so called because it appears to be rough due to its surface being covered with ribosomes, that functions to help cells process proteins in sacs called cisternae. The second type of ER is smooth ER and helps cells to process fats. ER generally contains enzymes to break down both proteins and fats.

What is endorphin (endogenous morphine or opiod) ?

A class of endogenous (made in the body) hormones produced in the brain and anterior pituitary that are chemically similar to opiate drugs (such as morphine) and are released to cope with acute stress and to deal with pain.

What is endoskeleton ?

An internal skeleton.

What is endosperm ?

A nutrient, food-storage tissue, formed from double fertilization (sperm cell fuses to two polar nuclei) in the seeds of angiosperms, which nourishes the developing embryo.

What is endospore ?

A thick-coated, environmentally resistant protective seedlike cell produced within a bacterial cell that is exposed to harsh conditions. In mycology, it is the term for spores formed on the inside of a sporangium; a spore produced within a spherule.

What is endosymbiotic theory ?

A theory on the evolution of eukaryotic cells. Originally mitochondria and chloroplasts were free-living self-replicating cells that developed a symbiotic relationship with prokaryote cells and eventually lost their independence.

What is endothelium ?

The simple thin layer of endothelial cells that lines blood and lymph vessels. It plays a number of roles, including acting as a selective barrier for molecules and cells between the blood and surrounding tissues, and secreting and modifying several veinous signaling molecules. The endothelium also helps to make up the blood-brain barrier between the central nervous system and the rest of the body; summons and captures white blood cells (leukocytes) to the site of infections; regulates coagulation of the blood at trauma sites; controls contraction and relaxation of veins; and regulates the growth of the veinous muscular cells, among others.

It is also the term used for the innermost layer of the eye’s cornea, one cell layer thick (5–10 microns or 0.005–0.01 millimeters), that provides hydration balance to maintain the cornea’s transparency.

What is endothelium-derived relaxing factor (EDRF ?

The factor originally described as EDRF is NO., produced by a specific P-450-type of ENZYME from arginine upon response of a cell to a biological signal (molecule). Different types of cells respond differently to the presence of NO..

What is endotherm ?

A warm-blooded animal, one is which the internal temperature does not fluctuate with temperature of environment, but is maintained by a constant internal temperature regulated by metabolic processes. Examples include birds and mammals.

What is A warm-blooded animal, one is which the internal temperature does not fluctuate with temperature of environment, but is maintained by a constant internal temperature regulated by metabolic processes. Examples include birds and mammals. ?

What is endothermic ?

The state of being warm-blooded or producing heat internally. In chemistry, it is a reaction where heat enters into a system, with the energy absorbed by a reactant.

What is endotoxin ?

A large toxic molecule consisting of polysaccharide, lipid A, and other components found in the outer cell wall of specific gram-negative bacteria. Also called pyrogen or lipopolysaccharide.

What is energy ?

Classically defined as the capacity for doing work, energy can occur in many forms such as heat (thermal), light, movement (mechanical), electrical, chemical, sound, or radiation. The first law of thermodynamics is often called the Law of Conservation of Energy and states that energy cannot be created or destroyed but only transformed from one form into another.

What is enhancer ?

A regulatory element of a gene. A site on DNA that increases transcription of a region even if it is distant from the transcribed region. One gene can have many enhancers.

What is entatic state ?

A state of an atom or group that, due to its binding in a protein, has its geometric or electronic condition adapted for function. Derived from the Greek entasis, meaning tension.

What is enterobactin ?

A SIDEROPHORE found in enteric bacteria such as Escherichia coli; sometimes called enterochelin.

What is entomology ?

The scientific study of the world of insects; a branch of zoology.

What is entomophilous ?

Refers to a flower pollinated by insects.

What is entropy ?

The amount of energy in a closed system that is not available for doing work; disorder and randomness in a system. The higher the entropy, the less energy available for work. The Second Law of Thermodynamics states that the entropy of the universe will always increase.

What is environment ?

The total living and nonliving conditions of an organism’s internal and external surroundings that affect an organism’s complete life span.

What is environmental grain ?

Describes an organism’s own perception of its environment and how it will react to it; a scale based on the use of space in relation to the size of an organism. Grains can be coarse (large patches) or fine (small patches).

What is enzootic ?

Affecting animals living in a specific area or limited region. Slime-blotch disease caused by Brooklynella hostilis and its associates caused a Caribbeanwide mass fish mortality in 1980 and similar ones in south Florida and Bermuda. In 1990, enzootic pneumonia, caused by Mycoplasma hyopneumoniae was evident in 80 percent of Iowa farms, and on these farms, 32 percent of the pigs were actively infected.

What is enzyme ?

A macromolecule that functions as a BIOCATALYST by increasing the reaction rate, frequently containing or requiring one or more metal ions. In general, an enzyme catalyzes only one reaction type (reaction specificity) and operates on only a narrow range of SUBSTRATES (substrate specificity). Substrate molecules are attacked at the same site (regiospecificity), and only one, or preferentially one of the ENANTIOMERs of chiral substrate or of RACEMIC mixtures, is attacked (enantiospecificity).

What is enzyme induction ?

The process whereby an (inducible) ENZYME is synthesized in response to a specific inducer molecule. The inducer molecule (often a substrate that needs the catalytic activity of the inducible enzyme for its METABOLISM) combines with a repressor and thereby prevents the blocking of an operator by the repressor leading to the translation of the gene for the enzyme. An inducible enzyme is one whose synthesis does not occur unless a specific chemical (inducer) is present, which is often the substrate of that enzyme.

What is enzyme repression ?

The mode by which the synthesis of an ENZYME is prevented by repressor molecules. In many cases, the end product of a synthesis chain (e.g., an amino acid) acts as a feedback corepressor by combining with an intracellular aporepressor protein, so that this complex is able to block the function of an operator. As a result, the whole operation is prevented from being transcribed into mRNA, and the expression of all enzymes necessary for the synthesis of the endproduct enzyme is abolished.

What is Eocene ?

Part of the Tertiary period during the Cenozoic era, lasting from about 54.8 to 33.7 million years ago. Most of the orders of truly warm-blooded mammals were present by the early Eocene.

What is eosinophil ?

One of the five different types of white blood cell (WBC) belonging to the subgroup of WBCs called polymorphonuclear leukocytes. Characterized by large red (i.e., eosinophilic) cytoplasmic granules.

What is eosinophil ?

One of the five different types of white blood cell (WBC) belonging to the subgroup of WBCs called polymorphonuclear leukocytes. Characterized by large red (i.e., eosinophilic) cytoplasmic granules.

Eosinophil function is incompletely understood. They are prominent at sites of allergic reactions and with parasitic larvae infections (helminths). Eosinophil secretory products inactivate many of the chemical mediators of inflammation and destroy cancer cells. This phenomenon is most obvious with mast-cellderived mediators. Mast cells produce a chemotactic factor for eosinophils.

Eosinophils are produced in the bone marrow, then migrate to tissues throughout the body. When a foreign substance enters the body, lymphocytes and neutrophils release certain substances to attract eosinophils, which release toxic substances to kill the invader.

What is eosinophil chemotactic factor of anaphylaxis (ECF-A) ?

A substrate released from mast cells and basophils during anaphylaxis, which attracts eosinophils. A tetrapeptide mediator of immediate hypersensi .

What is eosinophilia (blood eosinophilia) ?

An abnormally high number of eosinophils in the blood. Not a disease in itself but usually a response to a disease. An elevated number of eosinophils usually indicates a response to abnormal cells, parasites, or allergens.

What is epidermis ?

Both plants and animals have epidermis, the “skin.” Epidermis serves as a protective layer against invasion of foreign substances both chemical and animal (parasites).

In plants, it protects against desiccation; participates in gas exchange and secretion of metabolic compounds; absorbs water; and is the site of receptors for light and mechanical stimuli.

In mammals, the epidermis is a superficial layer of the skin and is subdivided into five layers or strata— the stratum corneum, the stratum basale, the stratum spinosum, the stratum granulosum, and the stratum lucidum—each with their own functions.

What is epigenesis ?

The complete and progressive development and differentiation that starts from the beginning of a fertilized egg or spore through each stage of change, guided by genetics and environment until the final adult stage is completed. A process where a genotype becomes expressed and transformed into a final phenotype.

What is epiglottis ?

A leaflike cartilaginous flap that closes and covers the glottis (middle part of the larynx) to prevent food and other objects from entering the trachea and lungs while ingesting.

What is epilepsy ?

A neurological or brain condition in which a person has a tendency to have repeated seizures. Clusters of nerve cells, or neurons, in the brain sometimes signal abnormally. It affects more than 2 million Americans, with over 180,000 new cases each year.

What is epinephrine ?

Another name for adrenaline. A hormone and neurotransmitter secreted by the adrenal gland (adrenal medulla) to react to stress, exercise, low blood glucose. It is also a major component of the fight-or-flight reaction, the reaction that happens in the body when, faced with a sudden unexpected threat or stress situation, both epinephrine and norepinephrine are released.

The drug of choice for the treatment of anaphylaxis. Individuals who are allergic to insect stings and certain foods should always carry a self-injecting syringe of epinephrine.

Epinephrine increases the speed and force of heartbeats and, therefore, the work that can be done by the heart. It dilates the airways to improve breathing and narrows blood vessels in the skin and intestine so that an increased flow of blood reaches the muscles and allows them to cope with the demands of exercise. Usually treatment with this hormone stops an anaphylactic reaction. Epinephrine has been produced synthetically as a drug since 1900.

What is epiparasite ?

Any organism that extracts nutrients from its host plant by means of intermediates.

What is epiphyte ?

Any nonparasitic plant, fungus, or microorganism that grows on the surface of another plant for support but provides its own nourishment. Epiphytes can form “mats” that contain a surface of canopy plants with suspended soil and other material. A facultative epiphyte is one that commonly grows epiphytically and terrestrially, but will usually exhibit a preference for one or the other habit in a particular habitat.

What is episome ?

A plasmid (circular piece of DNA ) that can attach to and integrate its DNA in a cell and at other times exist freely and still replicate itself alone, e.g., certain bacterial viruses.

What is epitasis ?

Interaction between nonallelic genes, with one gene altering the expression of the other gene.

What is epithelial tissues ?

Closely packed layers of epithelial cells, a membranelike tissue that covers the body and lines body cavities, such as the gastrointestinal tract and the lining of the lung. Epidermal growth factor (EGF) is a hormone that causes epithelial tissues, such as skin and the cells lining the gastrointestinal tract and lungs, to grow and heal.

What is epitope (antigenic determinant) ?

These are particular chemical groups on a molecule that are antigenic, i.e., that elicit a specific immune response.

What is epizootic ?

A rapid spread of a disease throughout an area affecting an animal group, e.g., rabies (disease affecting raccoons, fox) or epizootic catarrhal enteritis (disease affecting mink). When it occurs in humans, it is called an epidemic.

What is epoch ?

A period or date of time, shorter than and part of an era, that is used in geological time tables to locate historical events. Usually refers to an event (mountain building, appearance of a species, etc.). Also called a series.

What is equator ?

The area around the earth with a latitude of 0° that divides the Northern and Southern Hemispheres. It lies equidistant from the poles.

What is era ?

A period or date of time used in geological time tables to locate historical events. Usually refers to longer periods of time and marks a new or distinctive period.

Who was Erlanger, Joseph (1874–1965)

American Neuroscientist Joseph Erlanger was born on January 5, 1874, in San Francisco, California, to Herman and Sarah Erlanger. He received a B.S. in chemistry at the University of California and later attended Johns Hopkins University to study medicine, receiving an M.D. degree in 1899. He was appointed assistant in the department of physiology at the medical school, after spending a year of hospital training at Johns Hopkins Hospital, until 1906, moving up successively as instructor, associate, and associate professor. He was then appointed the first professor of physiology in the newly established Medical School of the University of Wisconsin. In 1910 he was appointed professor of physiology in the reorganized Medical School of the Washington University, St. Louis, retiring in 1946 as chairman of the school.

In 1922, in collaboration with his student Herbert Gasser, Erlanger adapted the cathode-ray oscillograph for the study of nerve-action potentials. They amplified the electrical responses of single nerve fibers and analyzed them by the use of the oscilloscope. The characteristic wave pattern of an impulse generated in a stimulated nerve fiber could be observed on the screen and the components of the nerve’s response studied.

Erlanger and Gasser were given the Nobel Prize in medicine or physiology in 1944 for this work. Erlanger later worked on the metabolism of dogs with shortened intestines, on traumatic shock, and on the mechanism of the production of sound in arteries.

With Gasser he wrote Electrical Signs of Nervous Activity (1937). He died on December 5, 1965, in St. Louis.

What is erythrocyte ?

A concave red blood cell that functions totally within the cardiovascular system. It does not have a nucleus or cytoplasmic organelles and produces little enzyme activity. It contains the red pigment hemoglobin, an oxygen-binding protein, and the cell functions as an efficient vessel for the exchange of respiratory gas. Originates from bone marrow in adult humans.

What is Escherichia coli ?

A gram-negative, rodlike bacterium that forms acid and gas in the presence of carbohydrates and is commonly found in human intestines and in many other animals. It can be pathogenic and is implicated in a number of food-borne illnesses, with an estimated 10,000 to 20,000 cases of infection occurring in the United States each year. There are hundreds of strains of this one species.

What is esophagus ?

The muscular tube of the digestive tract between the throat (pharynx) and stomach.

What is essential amino acids ?

Amino acids that cannot be synthesized in the human body and must be provided from another source (food). These amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

What is estivation (aestivation) ?

A state of stagnation or dormancy with slow metabolism (no eating, moving, or growing) during periods of hot temperature and little water supply; a physiological condition for survival.

What is estrogens ?

Primary female sex hormones. Estrogens cause growth and development of female sex organs and support the maintenance of sexual characteristics, including growth of underarm and pubic hair and shaping of body contours and skeleton; increase secretions from the cervix and growth of the endometrium (inner lining) of the uterus; and reduce concentrations of bad cholesterol (LDL cholesterol) while increasing good cholesterol (HDL). Estrogen is produced in the ovary by the developing follicle and by the corpus luteum.

What is estrous cycle (heat cycle) ?

The period from one ovulation to the next in female mammals; a period of sexual receptiveness preceding ovulation; in humans it occurs every 21 to 23 days. It is characterized by rising and falling levels of estrogens and progesterone in the bloodstream.

What is estrus ?

The “heat” cycle in reproduction, the time when the female is sexually receptive.

What is ethology ?

The study of natural animal behavior.

What is ethylene (C2H4) ?

A reactive chemical made from natural gas or crude-oil components (occurs naturally in both petroleum and natural gas) that acts as a plant hormone, the only gaseous hormone. It is used for accelerating fruit ripening (bananas); maturing citrus fruit color; increasing the growth rate of seedlings, vegetables, and fruit trees; leaf abscission; and aging.

What is etiology (aetiology) ?

The scientific study or theory of the causes of a certain disease.

What is euchromatin ?

Within a nucleus of eukaryotes there are two types of a mixture of nucleic acid and protein called chromatin that make up a chromosome: euchromatin and heterochromatin. During interphase, the genetically active euchromatin is uncoiled and is available for transcription, while heterochromatin is denser and usually not transcribed.

What is eudismic ratio ?

The POTENCY of the EUTOMER relative to that of the DISTOMER.

What is eukaryotes ?

Organisms whose cells have their GENETIC material packed in a membrane-surrounded, structurally discrete nucleus and who have well-developed cell organelles.

What is eumetazoa ?

A subkingdom of the animalia kingdom that includes all animals with the exception of sponges; animals with cells that form tissues and organs, a mouth, and digestive tract. Two branches exist, the radiata and the bilateria. The radiata have radial symmetry, i.e., all longitudinal planes are equal around a central body axis, while the bilateria are animals that have bilateral symmetry, i.e., they have a definite front and rear, and left and right body surfaces.

What is Eurasia ?

Europe plus Asia considered as one continent. Used in political, economic, and geographical terms.

What is eusocial ?

A social system of insects, belonging to the order Isoptera (termites) and the order Hymenoptera (ants, bees, and wasps), in which the individuals cooperate in caring for the young after one female produces offspring. There is a reproductive division of labor, and previous generations aid in rearing. This trait also occurs in two species of mammals

What is eutherian mammals (placental mammals) ?

The female has a placenta that is connected to an embryo within the uterus that supplies it with nutrients and oxygen and acts as an excretory system. Humans are eutherian mammals.

What is eutomer ?

The enantiomer of a chiral compound that is the more potent for a particular action.

What is eutrophication ?

The accelerated loading or dumping of nutrients in a lake by natural or human-induced causes. Natural eutrophication changes the character of a lake very gradually, sometimes taking centuries, but humanmade or cultural eutrophication speeds up the aging of a lake, changing its qualities quickly, often in a matter of years.

What is eutrophic lake ?

Any lake that has an excessive supply of nutrients, usually nitrates and phosphates. Eutrophic lakes are usually not deep, contain abundant algae or rooted plants, and contain limited oxygen in the bottom layer of water.

What is evaporative cooling ?

Temperature reduction when water absorbs latent heat from the surrounding air as it evaporates. Similarly, “cooling” of the skin from the evaporation of sweat is evaporative cooling and is a process for the body to lose excess heat.

What is evolution ?

The long process of change that occurs in populations of organisms. It began with the first life forms on Earth and created the diversity of life forms that exist today and that will exist in the future.

What is evolutionary species concept ?

A species comprises the totality of individuals that share a common evolutionary history. A species is a lineage evolving separately from others.

What is exaptation ?

The adoption of an attribute that had one function in an ancestral form but now has a new and different form, e.g., swim bladders becoming lungs, or three jaw bones of mammal ancestors becoming the middle bones of the ear. Formerly called preadaptation.

What is excitatory postsynaptic potential (EPSP) ?

Electrical change in the membrane of a postsynaptic neuron caused by binding of an excitatory neurotransmitter from a presynaptic cell to a postsynaptic receptor. Promotes firing of an action potential in the postsynaptic cell .

What is excretion ?

The process of separating and removing waste products of metabolism from the body through the discharge of urine, feces, or expired air.

What is exegetic reaction ?

A spontaneous reaction in which energy flows out of the system; a decrease in free energy. A reaction that liberates heat.

What is exobiology ?

The study of the origin of life other than on planet Earth.

What is exocytosis ?

The process in which a cell discharges large substances to the outside using secretory vesicles, storage organelles, that are then fused with the plasma membrane where they open for export.

What is exogenous ?

Originating externally. In the context of metalloprotein LIGANDs, exogenous describes ligands added from an external source, such as CO or O2.

What is exon ?

A section of DNA that carries the coding SEQUENCE for a protein or part of it. Exons are separated by intervening, noncoding sequences (called INTRONs). In EUKARYOTES, most GENEs consist of a number of exons.

What is exoskeleton ?

The hard external skeleton made from chitin and connective tissue that attaches it to the underlying parts of a body of animals such as arthropods (insects, spiders, crabs, lobsters). Serves as protection, antidessicant, and sensory interface with the environment.

What is exothermic ?

A reaction that produces heat and absorbs heat from the surroundings.

What is exotoxin ?

A toxic substance produced by bacteria and then released outside its cell into its environment.

What is exponential population growth ?

Rapid population growth; populations increase at a constant proportion from one generation to the next. For example, the human population is doubling every 40 years. The rate of increase is not limited by environmental factors, only biotic or intrinsic factors. If birth rates exceed death rates, population size will increase exponentially; likewise if death rates exceed birth, population size will decrease exponentially. Also known as J-shaped population growth.

What is expression ?

The cellular production of the protein encoded by a particular GENE. The process includes TRANSCRIPTION of DNA, processing of the resulting mRNA product, and its TRANSLATION into an active protein. A recombinant gene inserted into a host cell by means of a vector is said to be expressed if the synthesis of the encoded polypeptide can be demonstrated. For the expression of metalloproteins, usually other gene products will be required.

What is extended X-ray absorption fine structure (EXAFS) ?

EXAFS effects arise because of electron scattering by atoms surrounding a particular atom of interest as that special atom absorbs X rays and emits electrons. The atom of interest absorbs photons at a characteristic wavelength, and the emitted electrons, undergoing constructive or destructive interference as they are scattered by the surrounding atoms, modulate the absorption spectrum. The modulation frequency corresponds directly to the distance of the surrounding atoms, while the amplitude is related to the type and number of atoms. EXAFS studies are a probe of the local structure. EXAFS can be applied to systems that have local structure, but not necessarily long-range structure, such as noncrystalline materials. In particular, bond lengths and local symmetry (COORDINATION numbers) can be derived. The X-ray absorption spectrum can also show detailed structure below the absorption edge. This X-ray absorption near-edge structure (XANES) arises from excitation of core electrons to high-level vacant orbitals.

What is extinct species ?

A species no longer in existence.

What is extracellular matrix (ECM) ?

Material produced by animal cells and secreted into the surrounding area, serving as a glue to hold cells together in tissues. It is composed of proteoglycans, polysaccharides, and proteins. Plays a role in cell shape, growth, migration, and differentiation.

What is extraembryonic membranes ?

The YOLK SAC, AMNION, CHORION, AND ALLANTOIS, four membranes that support and nourish the developing embryo in reptiles, birds, and mammals. The allantois performs gas exchange and is a repository for the embryo’s nitrogenous waste. It is involved in the development of the urinary bladder. The chorion is the outermost layer and contributes to the formation of the placenta. The amnion, the innermost layer, forms a fluid-filled sac around the embryo to protect it from jarring. The yolk sac surrounds the yolk and is the site of blood-cell formation and germ-cell formation, which are the predecessors of male and female gametes.

What is extrinsic asthma ?

Asthma triggered by external agents such as pollen or chemicals. Most cases of extrinsic asthma have an allergic origin and are caused by an IgE-mediated response to an inhaled allergen. This is the type of asthma commonly diagnosed in early life. Many patients with extrinsic asthma respond to immunotherapy.