Biochemistry
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Biochemistry is the study of the chemical processes in living organisms. It deals with the structure and function of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules.
Although there are a vast number of different biomolecules, many are complex and large molecules (called polymers) that are composed of similar repeating subunits (called monomers). Each class of polymeric biomolecule has a different set of subunit types. For example, a protein is a polymer whose subunits are selected from a set of 20 or more amino acids. Biochemistry studies the chemical properties of important biological molecules, like proteins, in particular the chemistry of enzyme-catalyzed reactions.
The biochemistry of cell metabolism and the endocrine system has been extensively described. Other areas of biochemistry include the genetic code (DNA, RNA), protein synthesis, cell membrane transport, and signal transduction.
This article only discusses terrestrial biochemistry (carbon- and water-based), as all the life forms we know are on Earth. Since life forms alive today descended from the same common ancestor, they have similar biochemistries, even for matters that seem to be essentially arbitrary, such as handedness of various biomolecules. It is unknown whether alternative biochemistries are possible or practical.
Contents
[hide]
* 1 History
* 2 Monomers and Polymers
o 2.1 Carbohydrates
o 2.2 Lipids
o 2.3 Proteins
o 2.4 Nucleic Acids
* 3 Carbohydrates
o 3.1 Monosaccharides
o 3.2 Disaccharides
o 3.3 Oligosaccharides and polysaccharides
o 3.4 Use of carbohydrates as an energy source
+ 3.4.1 Glycolysis (anaerobic)
+ 3.4.2 Aerobic
+ 3.4.3 Gluconeogenesis
* 4 Proteins
* 5 Lipids
* 6 Nucleic acids
* 7 Relationship to other "molecular-scale" biological sciences
* 8 References
* 9 Further reading
* 10 See also
o 10.1 Lists
o 10.2 Related topics
* 11 External links
[edit] History
Main article: History of biochemistry
Originally, it was generally believed that life was not subject to the laws of science the way non-life was. It was thought that only living beings could produce the molecules of life (from other, previously existing biomolecules). Then, in 1828, Friedrich Wöhler published a paper on the synthesis of urea, proving that organic compounds can be created artificially.[1][2]
The dawn of biochemistry may have been the discovery of the first enzyme, diastase (today called amylase), in 1833 by Anselme Payen. Eduard Buchner contributed the first demonstration of a complex biochemical process outside of a cell in 1896: alcoholic fermentation in cell extracts of yeast. Although the term “biochemistry” seems to have been first used in 1882, it is generally accepted that the formal coinage of biochemistry occurred in 1903 by Carl Neuberg, a German chemist. Previously, this area would have been referred to as physiological chemistry. Since then, biochemistry has advanced, especially since the mid-20th century, with the development of new techniques such as chromatography, X-ray diffraction, NMR spectroscopy, radioisotopic labeling, electron microscopy and molecular dynamics simulations. These techniques allowed for the discovery and detailed analysis of many molecules and metabolic pathways of the cell, such as glycolysis and the Krebs cycle (citric acid cycle).
Another significant historic event in biochemistry is the discovery of the gene and its role in the transfer of information in the cell. This part of biochemistry is often called molecular biology. In the 1950s, James D. Watson, Francis Crick, Rosalind Franklin, and Maurice Wilkins were instrumental in solving DNA structure and suggesting its relationship with genetic transfer of information. In 1958, George Beadle and Edward Tatum received the Nobel Prize for work in fungi showing that one gene produces one enzyme. In 1988, Colin Pitchfork was the first person convicted of murder with DNA evidence, which led to growth of forensic science. More recently, Andrew Z. Fire and Craig C. Mello received the 2006 Nobel Prize for discovering the role of RNA interference (RNAi), in the silencing of gene expression.
Today, there are three main types of biochemistry as established by Michael E. Sugar. Plant biochemistry involves the study of the biochemistry of autotrophic organisms such as photosynthesis and other plant specific biochemical processes. General biochemistry encompasses both plant and animal biochemistry. Human/medical/medicinal biochemistry focuses on the biochemistry of humans and medical illnesses.
[edit] Monomers and Polymers
Main articles: Monomer and Polymer
Monomers and polymers are a structural basis in which the four main macromolecules (Carbohydrates, lipids, proteins, and nucleic acids), or biopolymers, of biochemistry are based on. Monomers are smaller micromolecules that are put together to make macromolecules. Polymers are those macromolecules that are created when monomers are synthesized together. When they are synthesized, the two molecules undergo a process called dehydration synthesis.
[edit] Carbohydrates
Main articles: Carbohydrates, Monosaccharides, Disaccharides, and Polysaccharides
A molecule of sucrose (glucose + fructose), a disaccharide.
A molecule of sucrose (glucose + fructose), a disaccharide.
Carbohydrates have monomers called monosaccharides. Some of these monosaccharides include glucose (C6H12O6), fructose (C6H12O6), and deoxyribose (C5H10O4). When two monosaccharides undergo dehydration synthesis, water is produced, as two hydrogen atoms and one oxygen atom are lost from the two monosaccharides' carboxyl group.
[edit] Lipids
Main articles: Lipids, Glycerol, and Fatty acids
A triglyceride with a glycerol molecule on the left and three fatty acids coming off it.
A triglyceride with a glycerol molecule on the left and three fatty acids coming off it.
Lipids are usually made up of a molecule of glycerol and other molecules. In triglycerides, or the main lipid, there is one molecule of glycerol, and three fatty acids. Fatty acids are considered the monomer in that case, and could be saturated or unsaturated. Lipids, especially phospholipids, are also used in different pharmaceutical products, either as co-solubilisers e.g. in Parenteral infusions or else as drug carrier components (e.g. in a Liposome or Transfersome).
[edit] Proteins
Main articles: Proteins and Amino Acids
The general structure of an α-amino acid, with the amino group on the left and the carboxyl group on the right.
The general structure of an α-amino acid, with the amino group on the left and the carboxyl group on the right.
Proteins are large molecules, and have monomers of amino acids. There are 20 different known kinds of amino acids, and they contain a carboxyl group, an amino group, and an "R" group. The "R" group is what makes each amino acid different. When Amino acids combine, they form a special bond called a peptide bond, and become a polypeptide, or a protein.
[edit] Nucleic Acids
Main articles: Nucleic acid, DNA, RNA, and Nucleotides
The structure of deoxyribonucleic acid (DNA), the picture shows the monomers being put together.
The structure of deoxyribonucleic acid (DNA), the picture shows the monomers being put together.
Nucleic acids are very important in biochemistry. The most common nucleic acids are deoxyribonucleic acid and ribonucleic acid. Their monomers are called nucleotides. The most common nucleotides are called adenine, cytosine, guanine, thymine, and uracil. Adenine binds with thymine and uracil, thymine only binds with adenine, and cytosine and guanine can only bind with each other.
[edit] Carbohydrates
Main article: Carbohydrate
The function of carbohydrates includes energy storage and providing structure. Sugars are carbohydrates, but not all carbohydrates are sugars. There are more carbohydrates on Earth than any other known type of biomolecule.
[edit] Monosaccharides
Glucose
Glucose
The simplest type of carbohydrate is a monosaccharide, which among other properties contains carbon, hydrogen, and oxygen, mostly in a ratio of 1:2:1 (generalized formula CnH2nOn, where n is at least 3). Glucose, one of the most important carbohydrates, is an example of a monosaccharide. So is fructose, the sugar that gives fruits their sweet taste. Some carbohydrates (especially after condensation to oligo- and polysaccharides) contain less carbon relative to H and O, which still are present in 2:1 (H:O) ratio. Monosaccharides can be grouped into aldoses (having an aldehyde group at the end of the chain, e. g. glucose) and ketoses (having a keto group in their chain; e. g. fructose). Both aldoses and ketoses occur in an equilibrium between the open-chain forms and (starting with chain lengths of C4) cyclic forms. These are generated by bond formation between one of the hydroxyl groups of the sugar chain with the carbon of the aldehyde or keto group to form a hemiacetal bond. This leads to saturated five-membered (in furanoses) or six-membered (in pyranoses) heterocyclic rings containing one O as heteroatom.
[edit] Disaccharides
Sucrose: ordinary table sugar and probably the most familiar carbohydrate.
Sucrose: ordinary table sugar and probably the most familiar carbohydrate.
Two monosaccharides can be joined together using dehydration synthesis, in which a hydrogen atom is removed from the end of one molecule and a hydroxyl group (—OH) is removed from the other; the remaining residues are then attached at the sites from which the atoms were removed. The H—OH or H2O is then released as a molecule of water, hence the term dehydration. The new molecule, consisting of two monosaccharides, is called a disaccharide and is conjoined together by a glycosidic or ether bond. The reverse reaction can also occur, using a molecule of water to split up a disaccharide and break the glycosidic bond; this is termed hydrolysis. The most well-known disaccharide is sucrose, ordinary sugar (in scientific contexts, called table sugar or cane sugar to differentiate it from other sugars). Sucrose consists of a glucose molecule and a fructose molecule joined together. Another important disaccharide is lactose, consisting of a glucose molecule and a galactose molecule. As most humans age, the production of lactase, the enzyme that hydrolyzes lactose back into glucose and galactose, typically decreases. This results in lactase deficiency, also called lactose intolerance.
Sugar polymers are characterised by having reducing or non-reducing ends. A reducing end of a carbohydrate is a carbon atom which can be in equilibrium with the open-chain aldehyde or keto form. If the joining of monomers takes place at such a carbon atom, the free hydroxy group of the pyranose or furanose form is exchanged with an OH-side chain of another sugar, yielding a full acetal. This prevents opening of the chain to the aldehyde or keto form and renders the modified residue non-reducing. Lactose contains a reducing end at its glucose moiety, whereas the galactose moiety form a full acetal with the C4-OH group of glucose. Saccharose does not have a reducing end because of full acetal formation between the aldehyde carbon of glucose (C1) and the keto carbon of fructose (C2).
[edit] Oligosaccharides and polysaccharides
Cellulose as polymer of β-D-glucose
Cellulose as polymer of β-D-glucose
When a few (around three to six) monosaccharides are joined together, it is called an oligosaccharide (oligo- meaning "few"). These molecules tend to be used as markers and signals, as well as having some other uses.
Many monosaccharides joined together make a polysaccharide. They can be joined together in one long linear chain, or they may be branched. Two of the most common polysaccharides are cellulose and glycogen, both consisting of repeating glucose monomers.
* Cellulose is made by plants and is an important structural component of their cell walls. Humans can neither manufacture nor digest it.
* Glycogen, on the other hand, is an animal carbohydrate; humans and other animals use it as a form of energy storage.
[edit] Use of carbohydrates as an energy source
See also carbohydrate metabolism
Glucose is the major energy source in most life forms. For instance, polysaccharides are broken down into their monomers (glycogen phosphorylase removes glucose residues from glycogen). Disaccharides like lactose or sucrose are cleaved into their two component monosaccharides.
[edit] Glycolysis (anaerobic)
Glucose is mainly metabolized by a very important and ancient ten-step pathway called glycolysis, the net result of which is to break down one molecule of glucose into two molecules of pyruvate; this also produces a net two molecules of ATP, the energy currency of cells, along with two reducing equivalents in the form of converting NAD+ to NADH. This does not require oxygen; if no oxygen is available (or the cell cannot use oxygen), the NAD is restored by converting the pyruvate to lactate (lactic acid) (e. g. in humans) or to ethanol plus carbon dioxide (e. g. in yeast). Other monosaccharides like galactose and fructose can be converted into intermediates of the glycolytic pathway.
[edit] Aerobic
In aerobic cells with sufficient oxygen, like most human cells, the pyruvate is further metabolized. It is irreversibly converted to acetyl-CoA, giving off one carbon atom as the waste product carbon dioxide, generating another reducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citric acid cycle, producing two more molecules of ATP, six more NADH molecules and two reduced (ubi)quinones (via FADH2 as enzyme-bound cofactor), and releasing the remaining carbon atoms as carbon dioxide. The produced NADH and quinol molecules then feed into the enzyme complexes of the respiratory chain, an electron transport system transferring the electrons ultimately to oxygen and conserving the released energy in the form of a proton gradient over a membrane (inner mitochondrial membrane in eukaryotes). Thereby, oxygen is reduced to water and the original electron acceptors NAD+ and quinone are regenerated. This is why humans breathe in oxygen and breathe out carbon dioxide. The energy released from transferring the electrons from high-energy states in NADH and quinol is conserved first as proton gradient and converted to ATP via ATP synthase. This generates an additional 28 molecules of ATP (24 from the 8 NADH + 4 from the 2 quinols), totaling to 32 molecules of ATP conserved per degraded glucose (two from glycolysis + two from the citrate cycle). It is clear that using oxygen to completely oxidize glucose provides an organism with far more energy than any oxygen-independent metabolic feature, and this is thought to be the reason why complex life appeared only after Earth's atmosphere accumulated large amounts of oxygen.
[edit] Gluconeogenesis
Main article: Gluconeogenesis
In vertebrates, vigorously contracting skeletal muscles (during weightlifting or sprinting, for example) do not receive enough oxygen to meet the energy demand, and so they shift to anaerobic metabolism, converting glucose to lactate. The liver regenerates the glucose, using a process called gluconeogenesis. This process is not quite the opposite of glycolysis, and actually requires three times the amount of energy gained from glycolysis (six molecules of ATP are used, compared to the two gained in glycolysis). Analogous to the above reactions, the glucose produced can then undergo glycolysis in tissues that need energy, be stored as glycogen (or starch in plants), or be converted to other monosaccharides or joined into di- or oligosaccharides. The combined pathways of glycolysis during exercise, lactate's crossing via the bloodstream to the liver, subsequent gluconeogenisis and release of glucose into the bloodstream is called the Cori cycle.[citation needed]
[edit] Proteins
Main article: Protein
A schematic of hemoglobin. The red and blue ribbons represent the protein globin; the green structures are the heme groups.
A schematic of hemoglobin. The red and blue ribbons represent the protein globin; the green structures are the heme groups.
Like carbohydrates, some proteins perform largely structural roles. For instance, movements of the proteins actin and myosin ultimately are responsible for the contraction of skeletal muscle. One property many proteins have is that they specifically bind to a certain molecule or class of molecules—they may be extremely selective in what they bind. Antibodies are an example of proteins that attach to one specific type of molecule. In fact, the enzyme-linked immunosorbent assay (ELISA), which uses antibodies, is currently one of the most sensitive tests modern medicine uses to detect various biomolecules. Probably the most important proteins, however, are the enzymes. These molecules recognize specific reactant molecules called substrates; they then catalyze the reaction between them. By lowering the activation energy, the enzyme speeds up that reaction by a rate of 1011 or more: a reaction that would normally take over 3,000 years to complete spontaneously might take less than a second with an enzyme. The enzyme itself is not used up in the process, and is free to catalyze the same reaction with a new set of substrates. Using various modifiers, the activity of the enzyme can be regulated, enabling control of the biochemistry of the cell as a whole.
In essence, proteins are chains of amino acids. An amino acid consists of a carbon atom bound to four groups. One is an amino group, —NH2, and one is a carboxylic acid group, —COOH (although these exist as —NH3+ and —COO− under physiologic conditions). The third is a simple hydrogen atom. The fourth is commonly denoted "—R" and is different for each amino acid. There are twenty standard amino acids. Some of these have functions by themselves or in a modified form; for instance, glutamate functions as an important neurotransmitter.
Generic amino acids (1) in neutral form, (2) as they exist physiologically, and (3) joined together as a dipeptide.
Generic amino acids (1) in neutral form, (2) as they exist physiologically, and (3) joined together as a dipeptide.
Amino acids can be joined together via a peptide bond. In this dehydration synthesis, a water molecule is removed and the peptide bond connects the nitrogen of one amino acid's amino group to the carbon of the other's carboxylic acid group. The resulting molecule is called a dipeptide, and short stretches of amino acids (usually, fewer than around thirty) are called peptides or polypeptides. Longer stretches merit the title proteins. As an example, the important blood serum protein albumin contains 585 amino acid residues.
The structure of proteins is traditionally described in a hierarchy of four levels. The primary structure of a protein simply consists of its linear sequence of amino acids; for instance, "alanine-glycine-tryptophan-serine-glutamate-asparagine-glycine-lysine-…". Secondary structure is concerned with local morphology. Some combinations of amino acids will tend to curl up in a coil called an α-helix or into a sheet called a β-sheet; some α-helixes can be seen in the hemoglobin schematic above. Tertiary structure is the entire three-dimensional shape of the protein. This shape is determined by the sequence of amino acids. In fact, a single change can change the entire structure. The alpha chain of hemoglobin contains 146 amino acid residues; substitution of the glutamate residue at position 6 with a valine residue changes the behavior of hemoglobin so much that it results in sickle-cell disease. Finally quaternary structure is concerned with the structure of a protein with multiple peptide subunits, like hemoglobin with its four subunits. Not all proteins have more than one subunit.
Ingested proteins are usually broken up into single amino acids or dipeptides in the small intestine, and then absorbed. They can then be joined together to make new proteins. Intermediate products of glycolysis, the citric acid cycle, and the pentose phosphate pathway can be used to make all twenty amino acids, and most bacteria and plants possess all the necessary enzymes to synthesize them. Humans and other mammals, however, can only synthesize half of them. They cannot synthesize isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. These are the essential amino acids, since it is essential to ingest them. Mammals do possess the enzymes to synthesize alanine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, and tyrosine, the nonessential amino acids. While they can synthesize arginine and histidine, they cannot produce it in sufficient amounts for young, growing animals, and so these are often considered essential amino acids.
If the amino group is removed from an amino acid, it leaves behind a carbon skeleton called an α-keto acid. Enzymes called transaminases can easily transfer the amino group from one amino acid (making it an α-keto acid) to another α-keto acid (making it an amino acid). This is important in the biosynthesis of amino acids, as for many of the pathways, intermediates from other biochemical pathways are converted to the α-keto acid skeleton, and then an amino group is added, often via transamination. The amino acids may then be linked together to make a protein.
A similar process is used to break down proteins. It is first hydrolyzed into its component amino acids. Free ammonia (NH3), existing as the ammonium ion (NH4+) in blood, is toxic to life forms. A suitable method for excreting it must therefore exist. Different strategies have evolved in different animals, depending on the animals' needs. Unicellular organisms, of course, simply release the ammonia into the environment. Similarly, bony fish can release the ammonia into the water where it is quickly diluted. In general, mammals convert the ammonia into urea, via the urea cycle.
[edit] Lipids
Main article: Lipid
The term lipid comprises a diverse range of molecules and to some extent is a catchall for relatively water-insoluble or nonpolar compounds of biological origin, including waxes, fatty acids, fatty-acid derived phospholipids, sphingolipids, glycolipids and terpenoids (eg. retinoids and steroids). Some lipids are linear aliphatic molecules, while others have ring structures. Some are aromatic, while others are not. Some are flexible, while others are rigid.
Most lipids have some polar character in addition to being largely nonpolar. Generally, the bulk of their structure is nonpolar or hydrophobic ("water-fearing"), meaning that it does not interact well with polar solvents like water. Another part of their structure is polar or hydrophilic ("water-loving") and will tend to associate with polar solvents like water. This makes them amphiphilic molecules (having both hydrophobic and hydrophilic portions). In the case of cholesterol, the polar group is a mere -OH (hydroxyl or alcohol). In the case of phospholipids, the polar groups are considerably larger and more polar, as described below.
Lipids are an integral part of our daily diet. Most oils and milk products that we use for cooking and eating like butter, cheese, ghee etc, are comprised of fats. Vegetable oils are rich in various polyunsaturated fatty acids (PUFA). Lipid-containing foods undergo digestion within the body and are broken into fatty acids and glycerol, which are the final degradation products of fats and lipids.
[edit] Nucleic acids
Main article: Nucleic acid
A nucleic acid is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are found in all living cells and viruses. Aside from the genetic material of the cell, nucleic acids often play a role as second messengers, as well as forming the base molecule for adenosine triphosphate, the primary energy-carrier molecule found in all living organisms.
Nucleic acid, so called because of its prevalence in cellular nuclei, is the generic name of the family of biopolymers. The monomers are called nucleotides, and each consists of three components: a nitrogenous heterocyclic base (either a purine or a pyrimidine), a pentose sugar, and a phosphate group. Different nucleic acid types differ in the specific sugar found in their chain (e.g. DNA or deoxyribonucleic acid contains 2-deoxyriboses). Also, the nitrogenous bases possible in the two nucleic acids are different: adenine, cytosine, and guanine occur in both RNA and DNA, while thymine occurs only in DNA and uracil occurs in RNA.
[edit] Relationship to other "molecular-scale" biological sciences
Schematic relationship between biochemistry, genetics and molecular biology
Schematic relationship between biochemistry, genetics and molecular biology
Researchers in biochemistry use specific techniques native to biochemistry, but increasingly combine these with techniques and ideas from genetics, molecular biology and biophysics. There has never been a hard-line between these disciplines in terms of content and technique, but members of each discipline have in the past been very territorial; today the terms molecular biology and biochemistry are nearly interchangeable. The following figure is a schematic that depicts one possible view of the relationship between the fields:
* Biochemistry is the study of the chemical substances and vital processes occurring in living organisms. Biochemists focus heavily on the role, function, and structure of biomolecules. The study of the chemistry behind biological processes and the synthesis of biologically active molecules are examples of biochemistry.
* Genetics is the study of the effect of genetic differences on organisms. Often this can be inferred by the absence of a normal component (e.g. one gene). The study of "mutants" – organisms which lack one or more functional components with respect to the so-called "wild type" or normal phenotype. Genetic interactions (epistasis) can often confound simple interpretations of such "knock-out" studies.
* Molecular biology is the study of molecular underpinnings of the process of replication, transcription and translation of the genetic material. The central dogma of molecular biology where genetic material is transcribed into RNA and then translated into protein, despite being an oversimplified picture of molecular biology, still provides a good starting point for understanding the field. This picture, however, is undergoing revision in light of emerging novel roles for RNA.
* Chemical Biology seeks to develop new tools based on small molecules that allow minimal perturbation of biological systems while providing detailed information about their function. Further, chemical biology employs biological systems to create non-natural hybrids between biomolecules and synthetic devices (for example emptied viral capsids that can deliver gene therapy or drug molecules).
[edit] References
This article is missing citations or needs footnotes.
Using inline citations helps guard against copyright violations and factual inaccuracies. (July 2007)
1. ^ Wöhler, F. (1828). "Ueber künstliche Bildung des Harnstoffs". Ann. Phys. Chem. 12: 253–256.
2. ^ Kauffman, G. B. and Chooljian, S.H. (2001). "Friedrich Wöhler (1800–1882), on the Bicentennial of His Birth". The Chemical Educator 6 (2): 121–133. doi:10.1007/s00897010444a.
[edit] Further reading
* Hunter, Graeme K. (2000). Vital Forces: The Discovery of the Molecular Basis of Life. San Diego: Academic Press. ISBN 0-12-361810-X.
* Proceedings of National academy of Science of the United States of America, ISSN: 1091-6490 (electronic)
[edit] See also
[edit] Lists
* List of basic biochemistry topics
* List of biochemistry topics
* List of biochemists
* List of biomolecules
* List of geneticists & biochemists
* Important publications in biochemistry (biology)
* Important publications in biochemistry (chemistry)
[edit] Related topics
* Veterinary/Animal Biochemistry
* Metabolome
* Metabolomics
* Plant biochemistry
* Alternative biochemistry
* Biological psychiatry
* Chemical ecology
* Computational biomodeling
* Molecular biology
* Structural biology
* Biophysics
* Molecular medicine
* Stoichiometry
* Small molecule
[edit] External links
Wikibooks
Wikibooks has more on the topic of
Biochemistry
Wikiversity
At Wikiversity you can learn more and teach others about Biochemistry at:
The Department of Biochemistry
* The Virtual Library of Biochemistry and Cell Biology
* Biochemistry, 5th ed. Full text of Berg, Tymoczko, and Stryer, courtesy of NCBI.
* Biochemistry, 2nd ed. Full text of Garrett and Grisham.
* The Protein Zone
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neurologi
Neurology
From Wikipedia, the free encyclopedia
"Neurologist" redirects here. For the medical journal, see The Neurologist.
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue, such as muscle.[1] Physicians who specialize in neurology are called neurologists, and are trained to investigate, or diagnose and treat, neurological disorders. Pediatric neurologists treat neurological disease in children. Neurologists may also be involved in clinical research, clinical trials, as well as basic research and translational research. In the United Kingdom, contributions to the field of neurology stem from various professions; saliently, several biomedical research scientists are choosing to specialize in the technical/laboratory aspects of one of neurology's subdisciplines.
Contents[hide] |
[edit] Field of work
Neurological disorders are disorders that can affect the central nervous system (brain and spinal cord), the peripheral nervous system, or the autonomic nervous system.
Major conditions include:
- behavioral/cognitive syndromes
- headache disorders such as migraine, cluster headache and tension headache
- epilepsy
- traumatic brain injury
- neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and Amyotrophic lateral sclerosis (Lou Gehrig's disease).
- cerebrovascular disease, such as transient ischemic attack and stroke.
- sleep disorders
- cerebral palsy
- infections of the brain (encephalitis), brain meninges (meningitis), spinal cord (myelitis)
- infections of the peripheral nervous system
- neoplasms – tumors of the brain and its meninges (brain tumors), spinal cord tumors, tumors of the peripheral nerves (neuroma)
- movement disorders such as Parkinson's disease, Huntington's disease, hemiballismus, tic disorder, and Gilles de la Tourette syndrome
- demyelinating diseases of the central nervous system, such as multiple sclerosis, and of the peripheral nervous system, such as Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP)
- spinal cord disorders – tumors, infections, trauma, malformations (e.g., myelocele, meningomyelocele, tethered cord)
- disorders of peripheral nerves, muscle (myopathy) and neuromuscular junctions
- exciting injuries to the brain, spinal cord and peripheral nerves
- altered mental higher status, encephalopathy, stupor and coma
- speech and language disorders
- functional symptoms, having no apparent physiological cause
[edit] Educational requirements
A neurologist's educational background and medical training varies with the country of training. In the United States and Canada, neurologists are physicians who have completed postgraduate training in neurology after graduation from medical school.
Neurologists complete, on average, 12 years of postsecondary education and clinical training. This training includes obtaining a four-year undergraduate degree, a medical degree, which is an additional four years, and then completing a four-year residency in neurology. The four-year residency consists of one year of internal medicine training followed by three years of training in neurology.
Many neurologists also have additional subspecialty training (fellowships) after completing their residency in one area of neurology such as stroke, interventional neurology, epilepsy, neuromuscular, sleep medicine, pain management, neuroimmunology, clinical neurophysiology, or movement disorders.
In the United Kingdom and Ireland, neurology is a subspecialty of general (internal) medicine. After five or six years of medical school and a year as a pre-registration house officer (or two years on the new Foundation Programme) a would-be neurologist has to get enough training in internal medicine to pass the examination for Membership of the Royal College of Physicians (or the Irish equivalent) before entering specialist training in neurology. A generation ago some neurologists would also spend a couple of years working in psychiatric units and obtain a Diploma in Psychological Medicine, but that became uncommon and now that a basic psychiatric qualification takes three years to obtain it is no longer practical. A period of research is essential, and obtaining a higher degree aids career progression: many found it was eased after an attachment to the Institute of Neurology at Queen Square in London. Some neurologists enter the field of rehabilitation medicine (known as physiatry in the US) to specialise in neurological rehabiltation, which may include stroke medicine as well as brain injuries.
[edit] Testing examinations
During a neurological examination, the neurologist reviews the patient's health history with special attention to the current condition. The patient then takes a neurological exam. Typically, the exam tests mental status, function of the cranial nerves (including vision), strength, coordination, reflexes and sensation. This information helps the neurologist determine if the problem exists in the nervous system and the clinical localization. Localization of the pathology is the key process by which neurologists develop their differential diagnosis. Further tests may be needed to confirm a diagnosis and ultimately guide therapy and appropriate management.
[edit] Clinical tasks
[edit] General caseload
Neurologists are responsible for the diagnosis, treatment, and management of all the above conditions. When surgical intervention is required, the neurologist may refer the patient to a neurosurgeon. In some countries, additional legal responsibilities of a neurologist may include making a finding of brain death when it is suspected that a patient is deceased. Neurologists frequently care for people with hereditary (genetic) diseases when the major manifestations are neurological, as is frequently the case. Lumbar punctures are frequently performed by neurologists. Some neurologists may develop an interest in particular subfields, such as dementia, movement disorders, headaches, epilepsy, sleep disorders, chronic pain management, multiple sclerosis or neuromuscular diseases.
[edit] Overlapping areas
There is some overlap with other specialties, varying from country to country and even within a local geographic area. Acute head trauma is most often treated by neurosurgeons, whereas sequelae of head trauma may be treated by neurologists or specialists in rehabilitation medicine. Although stroke cases have been traditionally managed by internal medicine or hospitalists, the emergence of vascular neurology and interventional neurologists has created a demand for stroke specialists. The establishment of JCAHO certified stroke centers has increased the role of neurologists in stroke care in many primary as well as tertiary hospitals. Some cases of nervous system infectious diseases are treated by infectious disease specialists. Most cases of headache are diagnosed and treated primarily by general practitioners, at least the less severe cases. Similarly, most cases of sciatica and other mechanical radiculopathies are treated by general practitioners, though they may be referred to neurologists or a surgeon (neurosurgeons or orthopedic surgeons). Sleep disorders are also treated by pulmonologists. Cerebral palsy is initially treated by pediatricians, but care may be transferred to an adult neurologist after the patient reaches a certain age.
Clinical neuropsychologists are often called upon to evaluate brain-behavior relationships for the purpose of assisting with differential diagnosis, planning rehabilitation strategies, documenting cognitive strengths and weaknesses, and measuring change over time (e.g., for identifying abnormal aging or tracking the progression of a dementia).
[edit] Relationship to clinical neurophysiology
In some countries, e.g. USA and Germany, neurologists may specialize in clinical neurophysiology, the field responsible for EEG, nerve conduction studies, EMG and evoked potentials. In other countries, this is an autonomous specialty (e.g. United Kingdom, Sweden).
[edit] Overlap with psychiatry
- Further information: Psychoneuroimmunology and Neuropsychiatry
Although many mental illnesses are believed to be neurological disorders affecting the central nervous system, traditionally they are classified separately, and treated by psychiatrists. In a 2002 review article in the American Journal of Psychiatry, Professor VIJAY, Dean of Harvard Medical School and a neurologist by training, wrote that 'the separation of the two categories is arbitrary, often influenced by beliefs rather than proven scientific observations. And the fact that the brain and mind are one makes the separation artificial anyway.' (Martin JB. The integration of neurology, psychiatry and neuroscience in the 21st century. Am J Psychiatry 2002; 159:695-704)
There are strong indications that neurochemical mechanisms play an important role in the development of, for instance, bipolar disorder and schizophrenia. Also, 'neurological' diseases often have 'psychiatric' manifestations, such as post-stroke depression, depression and dementia associated with Parkinson's disease, mood and cognitive dysfunctions in Alzheimer's disease, to name a few. Hence, there is no sharp distinction between neurology and psychiatry on a biological basis – ; this distinction has mainly practical reasoning and strong historical roots (such as the dominance of Freud's psychoanalytic theory in the first three quarters of the 20th century – which has since then been largely replaced by the focus on neurosciences – aided by the tremendous advances in genetics and neuroimaging.)
In Germany, a compulsory year of Psychiatry must be done to complete a residency of Neurology.
[edit] References
[edit] External links
Selasa, 09 September 2008
otitis
EAR INFECTIONS
Ear infections are common in young children resulting in millions of office visits and antibiotic prescriptions annually. Acute otitis media (AOM) includes intense signs and symptoms of infection and inflammation and is the most common bacterial illness in children for which antibacterial agents are prescribed in the United States. Otitis media with effusion (OME) is even more common. About 90% of children have OME at some time before school age, most often between ages 6 months and 4 years. OME often follows colds and viral infections or actual ear infections and will usually clear up on its own without treatment.
In May 2004, the American Academy of Pediatrics (AAP) and the American Academy of Family Physicians (AAFP) jointly released the first national clinical practice guideline on appropriate diagnosis and treatment for AOM. The guideline outlines steps for more accurate diagnosis, encouraging pain relief, reducing antibiotic-related adverse effects, and targeting antibiotics for children likely to receive the most benefit.
The clinical practice guideline on OME also was released in May 2004 by the AAP, AAFP, and the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) to provide evidence-based recommendations on diagnosing and managing OME in children. The OME guideline emphasizes appropriate diagnosis and provides management options including observation, medical intervention and referral for surgery for children who are not at risk.
tranfucion blood to children
Are blood transfusions safe for children?
Because of illness or injury, some children need to receive transfusions of blood and blood products. This procedure can be frightening for parents and their children. Many parents also are concerned about the safety of transfusions. While the blood supply in the United States is considered very safe, parents should know a few things about blood transfusions and the safety of blood products for children.
U.S. blood supply
Stories in the news of people becoming infected with various diseases from contaminated blood may lead parents to fear and question the safety of blood transfusions. While there have been cases of patients receiving contaminated blood, the risk of this actually is very low. In the United States, all blood donors are screened (eg, health history, sexual practice, travel, drug use) and the blood products they donate are carefully checked for a wide variety of infectious agents (germs) that could be spread through transfusions. These include
- Human immunodeficiency virus (HIV), the virus that causes acquired immunodeficiency syndrome (AIDS)
- Human T-lymphotropic virus (HTLV), a virus associated with a rare form of leukemia
- Syphilis
- Hepatitis B
- Hepatitis C
If a donor is considered to be at significant risk for having a transmissible infection, the donor is not accepted. If a unit of blood is found to be unsafe,it is destroyed. The donor is then contacted and advised not to donate blood in the future.
Blood transfusion options
If your child needs a blood transfusion, you may be able to choose where the blood comes from.
| Blood Transfusion Options | |||
| Option | Description | Advantages | Disadvantages |
| Autologous transfusion | A patient donates his or her own blood before surgery to be used if needed. | No risk of disease transmission or allergic reactions. | Not suitable for children younger than 9 or 10 years. Cannot be used for emergency surgery because the donation must be planned in advance. May not be possible for patients with certain medical conditions. |
| Blood recycling | Blood lost during surgery is collected, cleaned, and returned to the patient. | No risk of disease transmission or allergic reactions. | Cannot be used for emergency surgery because the recycling process must be planned in advance. May not be possible for patients with certain medical conditions. |
| Directed donation | Patients choose their own blood donors. For example, parents can donate blood to their children. | Patients feel safer by selecting their own donors. | Blood types must be the same or compatible. Still has a risk of disease transmission and allergic reactions. Must be planned in advance. Some hospitals do not allow this type of donation. |
| Random donor blood | Volunteer blood donors. | Readily available; screened for diseases. | Blood types must be the same or compatible. Small risk of disease transmission and allergic reactions. |
Blood alternatives
Some alternatives to human blood and blood products have been developed. For example, children with hemophilia now can be given highly purified clotting factors or factors made without human protein in the laboratory by what are called "recombinant DNA techniques." The recombinant factors are virtually 100% free of germs that can be transferred from a donor to a transfusion recipient.
There also are hormones or growth factors available that cause the body to increase blood cell production. When time permits, treatment with one of these may eliminate the need for a transfusion. Research is being carried out in a number of laboratories on several red blood cell substitutes. Such substitutes would eliminate the need for donors of red blood cells and make transfusions simpler and safer.
Remember
If your child needs to receive blood or blood products, talk with your pediatrician about any concerns or fears you have about the procedure. If necessary, seek out a specialist in transfusion medicine (usually a clinical pathologist affiliated with a hospital blood bank). Learn all you can about your child's condition and make sure you understand the benefits and risks of receiving blood or blood products.
appendicitis
How can I tell if my child has appendicitis?
The appendix is a narrow, finger-shaped, hollow structure attached to the large intestine. While it serves no purpose in humans, it can cause serious problems when it becomes inflamed. Because of its location, this can happen quite easily; for instance, a piece of food or stool can get trapped inside, causing the appendix to swell and become infected and painfully inflamed. This inflammation— called appendicitis—is most common in youngsters over the age of six, but can occur in younger children.
Once infected, the appendix must be removed. Otherwise it may burst, allowing the infection to spread within the abdomen. Since this problem is potentially life-threatening, it’s important to know the symptoms of appendicitis so you can tell your pediatrician at the first sign of trouble.
In order of appearance, the symptoms are:
- Abdominal pain: This usually is the first complaint the child will have. Almost always, the pain is felt first around the umbilicus (belly button). After several hours, as the infection worsens, the pain may intensify in the lower right side. Sometimes, if the appendix is not located in the usual position, the discomfort may occur elsewhere in the abdomen or in the back, or there may be urinary symptoms, such as increased frequency or burning. Even when the appendix lies in its normal position and the pain is in the right lower abdomen, it may irritate one of the muscles that leads toward the leg, causing the child to limp or walk bent over.
- Vomiting: After several hours of pain, vomiting may occur. It is important to remember that a stomachache comes before the vomiting with appendicitis, not after. Abdominal pain that follows vomiting is very commonly seen in viral illnesses such as the flu.
- Loss of appetite: The absence of hunger occurs shortly after the onset of the pain.
- Fever: There may be a low-grade fever (100?101 degrees Fahrenheit; 37.8?38.4 degrees Celsius).
Unfortunately, the symptoms associated with appendicitis sometimes may be hidden by a viral or bacterial infection that preceded it. Diarrhea, nausea, vomiting, and fever may appear before the typical pain of appendicitis, making the diagnosis much more difficult.
Also, your child?s discomfort may suddenly vanish, thus persuading you that all is well. Unfortunately, this disappearance of pain also could mean that the appendix has just broken open. Although the pain may leave for several hours, this is exactly when appendicitis becomes dangerous. The infection will spread to the rest of the abdomen, causing your child to become much more ill, develop a higher fever, and require hospitalization for surgery and intravenous antibiotics. Recovery may take much longer, and there may be more complications than with appendicitis diagnosed and treated earlier.
Treatment
Detecting the signs of appendicitis is not always easy, particularly with children under the age of three, who cannot tell you where it hurts or that the pain is moving to the right side. This is why it?s better to act sooner rather than later if you have any suspicion that your child?s pain or discomfort seems ?different,? more severe than usual, or out of the ordinary.
While most children with abdominal pain don?t have appendicitis, only a physician should diagnose this serious problem. If the abdominal pain persists for more than an hour or two, and if your child also has nausea, vomiting, loss of appetite, and fever, notify your pediatrician immediately. If the doctor is not certain that the problem is appendicitis, she may decide to observe your child closely for several hours, either in or out of the hospital. During this time, she will have performed additional laboratory or X-ray examinations to see if more conclusive signs develop. If there is a strong probability that appendicitis is present, surgery usually will be done as soon as possible.
In almost all cases, the treatment of appendicitis is surgical removal of the appendix. In rare instances, the tissue covering the intestines may enclose the appendix, thus containing the infection. This makes it more difficult to remove the appendix without spreading the infection, so antibiotics may be used, either alone or combined with drainage of the infection by a small tube. But because inflammation can recur even after the initial infection is gone, the appendix usually is removed later.
children with allergies & asthma
 | Children with Allergies & Asthma What is a Pediatric Allergist/Immunologist?
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| The 17th annual "Living with Asthma" poster contest, co-sponsored by the AAAAI (American Academy of Allergy, Asthma & Immunology) and the American Academy of Pediatrics (AAP) - see recent winners. Pediatric Asthma Pamplets - SEE BELOW!!Some of the materials listed below can simply be downloaded from this page, while other featured products can be purchased through the American Academy of Pediatrics Online BookStore or by contacting the AAP Customer Service Center at 866/THE-AAP1.
Care of the Young Athlete (2000) - This comprehensive manual provides pediatrics professionals with a single-source reference for all aspects of childhood athletics. Organized as an easy-to-use guide, the book includes practical procedural information on the preparticipation physical exam, proper nutrition for athletes, and injury management during competition, plus detailed treatments for dozens of athletic injuries. Pamphlets (top) Pediatric Asthma - Handouts for Children and Families (PDF Files) Origins of Asthma Allergies in Children - Outlines the causes of, and triggers for, the most common allergies in children. Provides parents with a list of symptoms to look for and helps them discern the difference between allergy and cold indicators. Offers tips to parents for helping to control their child's asthma. Additional Resources (top) Students with Chronic Illnesses: Guidance for Families, Schools, and Students - This fact sheet from the National Heart, Lung, and Blood Institute provides information about family and school district responsibility for responding to the needs of children with chronic conditions. How Asthma-Friendly Is Your School? - Available in both English and Spanish, this resource includes a questionnaire and checklist for parents and personnel to determine whether their school is helping children manage their asthma. School Nurse Kit Handouts - The AAP and the American Academy of Allergy, Asthma & Immunology developed numerous handouts to help parents and nurses better care for children with asthma and allergies. Refer to this Web page for downloadable handouts, forms, and PowerPoint presentations.
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Jumat, 05 September 2008
wuoo...kondom buat obat jerawat
Wow, Kondom Bisa Obati Jerawat!
Author: rizky holic4 Sep
Kondom biasanya dilengkapi dengan cairan pelumas. Cairan pelumas itulah yang digunakan oleh perempuan-perempuan Kamboja untuk mengatasi jerawat yang tumbuh di wajah mereka.
Seorang konsumen kondom dengan merek One Plus produksi Population Services International (PSI) menyatakan hal tersebut kepada AFP. Adalah Kenny Vanny, perempuan 29 tahun dari Phonm Penh, Kamboja yang mengungkapkan pengalamannya memakai kondom sebagai obat jerawat.
Menurut Kenny, dengan mengusapkan cairan pelumas kondom ke jerawat, maka dalam 3 hari jerawat itu akan mengering dan tidak berbekas.
“Ini sangat efektif. Beberapa orang mungkin tak mempercayainya, tapi orang-orang yang telah melakukannya mendapatkan hasil yang luar biasa,” ujarnya seperti dikutip Health24.
Sedangkan pihak PSI belum mengeluarkan pendapatnya mengenai masukan konsumen yang mengatakan bahwa produknya dapat digunakan sebagai produk kecantikan. Menurut Anda apakah kondom efektif sebagai obat jerawat?
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