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Encyclopedia > Biological half life

The biological halflife of a substance is the time required for half of that substance to be removed from an organism by either a physical or a chemical process.


While a radioactive substance decays perfectly according to first order kinetics where the rate constant is fixed, the elimination of a substance from a living organism follows more complex kinetics. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... Kinetics refers to two different areas of science: Chemical kinetics studies reaction rates. ...

Contents


Alcohol

For instance, the removal of ethanol (alcohol) through oxidation by alcohol dehydrogenase in the liver from the human body is limited. Hence the removal of a large concentration of alcohol from blood may follow zero order kinetics. Also the rate limiting steps for one substance may be in common with other substances. For instance, the blood alcohol concentration can be used to modify the biochemistry of methanol and ethylene glycol. In this way the oxidation of methanol to the toxic formaldehyde and formic acid in the human body can be prevented by giving a person who has ingested methanol an alcoholic drink. Note that methanol is very toxic and causes blindness and death. A person who has ingested ethylene glycol can be treated in the same way. Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless chemical compound, one of the alcohols that is most often found in alcoholic beverages. ... In chemistry, alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom, which in turn is bound to other hydrogen and/or carbon atoms. ... Alcohol Dehydrogenase Alcohol dehydrogenases are a group of dehydrogenase enzymes that occur in many organisms and facilitate the conversion between alcohols and aldehydes or ketones. ... The liver is one of the largest internal organs of the human body. ... Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... Methanol, also known as methyl alcohol or wood alcohol, is a chemical compound with chemical formula CH3OH. It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a very faint odor. ... Ethylene glycol (monoethylene glycol (MEG), IUPAC name: ethane-1,2-diol) is an alcohol with two -OH groups (a diol), a chemical compound widely used as an automotive antifreeze. ... Toxic redirects here, but this is also the name of a song by Britney Spears; see Toxic (song) Look up toxic and toxicity in Wiktionary, the free dictionary. ... The chemical compound formaldehyde (also known as methanal), is a gas with a strong pungent smell. ... Formic acid (systematically called methanoic acid) is the simplest carboxylic acid. ... In general terms, eating (formally, ingestion) is the process of consuming something edible, i. ... Blindness can be defined physiologically as the condition of lacking visual perception. ...


Water

The biological half life of water in a human is about 7 to 10 days. It can be altered by behaviour. Drinking large amounts of beer will reduce the biological half life of water in the body. This has been used to decontaminate humans who are internally contaminated with tritiated water (tritium). Drinking the same amount of water would have a similar effect, but many would find it difficult to drink a large volume of water. The basis of this decontamination method (used as Harwell) is to increase the rate at which the water in the body is replaced with new water. Beer, generally, is an alcoholic beverage produced through the fermentation of sugars suspended in an aqueous medium, and which is not distilled after fermentation. ... Tritium (symbol T or 3H) is a radioactive isotope of hydrogen. ... Harwell may refer to: Harwell - a village in Oxfordshire RAF Harwell - a World War II RAF airfield Harwell Laboratory of the Atomic Energy Research Establishment, the site of Europes first nuclear reactor. ...


Metals

The biological half life of caesium in humans is between one and four months. This can be shortened by feeding the person prussian blue. The prussian blue in the digestive system acts as a solid ion exchanger which absorbs the caesium while releasing potassium ions. General Name, Symbol, Number caesium, Cs, 55 Chemical series alkali metals Group, Period, Block 1, 6, s Appearance silvery gold Atomic mass 132. ... A sample of prussian blue Prussian blue (Preußisch Blau, Berliner Blau) is a dark blue pigment used in paints and formerly in blueprints. ... Ion exchange is a process in which ions are exchanged between a solution and an ion exchanger, an insoluble solid or gel. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Atomic mass 39. ...


For some substance, is it important to think of the human or animal body as being made up of several parts, each with their own affinity for the substance, and each part with a different biological half life. Attempts to remove a substance from the whole organism may have the effect of increasing the burden present in one part of the organism. For instance, if a person who is contaminated with lead is given EDTA in a chelation therapy, then while the rate at which lead is lost from the body will be increased, the lead within the body tends to relocate into the brain where it can do the most harm. EDTA EDTA is the chemical compound ethylenediaminetetraacetic acid, otherwise known as edetate, versene, or diaminoethanetetraacetic acid disodium salt. ... Chelation therapy is a process involving the use of chelating agents such as EDTA to remove heavy metals from the body. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ...

  • Cesium in the body has a biological half life of about one to four months.
  • Lead in bone has a biological half life of about ten years.
  • Cadmium in bone has a biological half life of about 30 years.
  • Plutonium in bone has a biological half life of about 100 years.
  • Plutonium in the liver has a biological half life of about 40 years.

A substance can have an effect on the health of a person long after the substance has left the body. For example, a car crash under the influence of chemicals may have consequences long into the future. A carcinogenic substance may cause cancer cells to appear, which may continue to multiply even after exposure to the carcinogen has stopped. This article is about the chemical element. ... Grays illustration of a human femur, a typically recognized bone. ... General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Atomic mass 112. ... General Name, Symbol, Number plutonium, Pu, 94 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery white Atomic mass (244) g/mol Electron configuration [Rn] 5f6 7s2 Electrons per shell 2, 8, 18, 32, 24, 8, 2 Physical properties Phase solid Density (near r. ... In pathology, a carcinogen is any substance or agent that promotes cancer. ...


Prozac

Also, some substances migrate slowly from the brain to the blood, for instance Prozac {N-methyl-3-phenyl-3-(4-trifluoromethylphenoxy) propyl amine} remains a long time in the brain because it is lipophilic. This is one of the things which makes prozac's biological halflife in the brain long. Background Fluoxetine hydrochloride (brand names include Prozac®, Symbyax® (compounded with olanzapine), Sarafem®, Fontex® (Sweden), Fluctine (Austria, Germany), Prodep (India), Fludac (India)) is an antidepressant drug used medically in the treatment of depression, obsessive-compulsive disorder, bulimia nervosa, premenstrual dysphoric disorder, and many other disorders. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ...


 
 

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