| 释义 |
protein
proteinplants or animal compounds rich in amino acids required for growth and repair of animal tissue
Not to be confused with:protean – extremely variable; changeable in shape or form, as an amoeba; a versatile actorpro·tein P0613400 (prō′tēn′, -tē-ĭn)n. Any of a group of complex organic macromolecules that contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur and are composed of one or more chains of amino acids. Proteins are fundamental components of all living cells and include many substances, such as enzymes, hormones, and antibodies, that are necessary for the proper functioning of an organism. They are essential in the diet of animals for the growth and repair of tissue and can be obtained from foods such as meat, fish, eggs, milk, and legumes.
[French protéine, from Late Greek prōteios, of the first quality, from Greek prōtos, first; see per in Indo-European roots.]
pro′tein·a′ceous (prōt′n-ā′shəs, prō′tē-nā′-), pro·tein′ic (prō-tē′nĭk), pro·tein′ous (prō-tē′nəs) adj.protein (ˈprəʊtiːn) n (Biochemistry) any of a large group of nitrogenous compounds of high molecular weight that are essential constituents of all living organisms. They consist of one or more chains of amino acids linked by peptide bonds and are folded into a specific three-dimensional shape maintained by further chemical bonding[C19: via German from Greek prōteios primary, from protos first + -in] ˌproteinˈaceous, proˈteinic, proˈteinous adjpro•tein (ˈproʊ tin, -ti ɪn)
n. 1. any of numerous organic molecules constituting a large portion of the mass of every life form, composed of 20 or more amino acids linked in one or more long chains, the final shape and other properties of each protein being determined by the side chains of the amino acids and their chemical attachments. 2. plant or animal tissue rich in such molecules, considered as a food source. [< French protéine (1838) < Greek prōte(îos) primary + French -ine -in1] pro`tein•a′ceous (-tiˈneɪ ʃəs, -ti ɪˈneɪ-) adj. pro·tein (prō′tēn′) One of a large class of complex organic chemical compounds that are essential for life. Proteins play a central role in biological processes and form the basis of living tissues. They consist of long, looping or folding chains of smaller compounds called amino acids. Enzymes, antibodies, and hemoglobin are examples of proteins.protein- albumen, albumin - Albumen is the white of an egg, from Latin albus, "white"; albumin is a protein within the albumen.
- protein - Pronounced PRO-teen or PRO-tee-un, it comes from Greek proteios, "primary," as these compounds are essential to all living organisms.
- protoplasm - A mixture of organic and inorganic substances, such as protein and water, it is regarded as the physical basis of life.
- textured vegetable protein - A protein obtained from soy beans and made to resemble minced meat.
Thesaurus| Noun | 1. |  protein - any of a large group of nitrogenous organic compounds that are essential constituents of living cells; consist of polymers of amino acids; essential in the diet of animals for growth and for repair of tissues; can be obtained from meat and eggs and milk and legumes; "a diet high in protein"capsid - the outer covering of protein surrounding the nucleic acid of a virusgluten - a protein substance that remains when starch is removed from cereal grains; gives cohesiveness to doughmeat - the flesh of animals (including fishes and birds and snails) used as foodlegume - the seedpod of a leguminous plant (such as peas or beans or lentils)eggs, egg - oval reproductive body of a fowl (especially a hen) used as foodmilk - a white nutritious liquid secreted by mammals and used as food by human beingsamino acid, aminoalkanoic acid - organic compounds containing an amino group and a carboxylic acid group; "proteins are composed of various proportions of about 20 common amino acids"recombinant protein - a protein derived from recombinant DNAactomyosin - a protein complex in muscle fibers; composed of myosin and actin; shortens when stimulated and causes muscle contractionsaleurone - granular protein in outermost layer of endosperm of many seeds or cereal grainsamyloid - (pathology) a waxy translucent complex protein resembling starch that results from degeneration of tissueapoenzyme - a protein that combines with a coenzyme to form an active enzymecompound protein, conjugated protein - a protein complex combining amino acids with other substancesenzyme - any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactionsfibrin - a white insoluble fibrous protein formed by the action of thrombin on fibrinogen when blood clots; it forms a network that traps red cells and plateletsfilaggrin - the main protein of the keratohyalin granules; "the specific target of the immune response in rheumatoid arthritis is filaggrin"growth factor - a protein that is involved in cell differentiation and growthhaptoglobin - a protein in plasma that binds free hemoglobin and removes it (as from wounds)iodinated protein, iodoprotein - a protein that contains iodinenucleoprotein - any of several substances found in the nuclei of all living cells; consists of a protein bound to a nucleic acidopsin - retinal protein formed by the action of light on rhodopsinphosphoprotein - containing chemically bound phosphoric acidplasma protein - any of the proteins in blood plasmaprostate specific antigen, PSA - a protein manufactured exclusively by the prostate gland; PSA is produced for the ejaculate where it liquifies the semen and allows sperm cells to swim freely; elevated levels of PSA in blood serum are associated with benign prostatic hyperplasia and prostate cancerproteome - the full complement of proteins produced by a particular genomesimple protein - a protein that yields only amino acids when hydrolyzedpolypeptide - a peptide containing 10 to more than 100 amino acidscytokine - any of various protein molecules secreted by cells of the immune system that serve to regulate the immune systemferritin - a protein containing 20% iron that is found in the intestines and liver and spleen; it is one of the chief forms in which iron is stored in the bodymacromolecule, supermolecule - any very large complex molecule; found only in plants and animalsantibody - any of a large variety of proteins normally present in the body or produced in response to an antigen which it neutralizes, thus producing an immune response |
proteinProteins actin, actomyosin, aleurone, alpha-fetoprotein, amyloid, apoprotein, avidin, calmodulin, caseinogen, conchiolin, dystrophin, factor VIII, ferritin, fibrin, fibrinogen, fibroin, flagellin, gliadin, globin, gluten, hordein, keratin, lactalbumin, lactoprotein, lectin, legumin, leptin, lymphokine, myosin, opsin, ossein, prion, properdin, ricin, sclerotin, sericin, spongin, thrombogen, vitellin, zeinTranslationsprotein (ˈprəutiːn) noun any of a large number of substances present in milk, eggs, meat etc, which are necessary as part of the food of human beings and animals. 蛋白質 蛋白质
protein
protein, any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight. Hundreds of protein molecules have been isolated in pure, homogeneous form; many have been crystallized. All contain carbon, hydrogen, and oxygen, and nearly all contain sulfur as well. Some proteins also incorporate phosphorous, iron, zinc, and copper. Proteins are large molecules with high molecular weights (from about 10,000 for small ones [of 50–100 amino acids] to more than 1,000,000 for certain forms); they are composed of varying amounts of the same 20 amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
..... Click the link for more information. , which in the intact protein are united through covalent chemical linkages called peptidepeptide,
organic compound composed of amino acids linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) of one amino acid and the amino nitrogen of a second amino acid.
..... Click the link for more information. bonds. The amino acids, linked together, form linear unbranched polymeric structures called polypeptide chains; such chains may contain hundreds of amino-acid residues; these are arranged in specific order for a given species of protein. Types of Proteins A protein molecule that consists of but a single polypeptide chain is said to be monomeric; proteins made up of more than one polypeptide chain, as many of the large ones are, are called oligomeric. Based upon chemical composition, proteins are divided into two major classes: simple proteins, which are composed of only amino acids, and conjugated proteins, which are composed of amino acids and additional organic and inorganic groupings, certain of which are called prosthetic groupsprosthetic group,
non-amino acid portions of certain protein molecules. The key part of the prosthetic group may be either organic (such as a vitamin) or inorganic (such as a metal) and is usually required for biological activity, especially when the prosthetic group is
..... Click the link for more information. . Conjugated proteins include glycoproteinsglycoprotein
, organic compound composed of both a protein and a carbohydrate joined together in covalent chemical linkage. These structures occur in many life forms; they are prevalent and important in mammalian tissues.
..... Click the link for more information. , which contain carbohydrates; lipoproteinslipoprotein
, any organic compound that is composed of both protein and the various fatty substances classed as lipids, including fatty acids and steroids such as cholesterol.
..... Click the link for more information. , which contain lipids; and nucleoproteins, which contain nucleic acidsnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
..... Click the link for more information. . Classified by biological function, proteins include the enzymesenzyme,
biological catalyst. The term enzyme comes from zymosis, the Greek word for fermentation, a process accomplished by yeast cells and long known to the brewing industry, which occupied the attention of many 19th-century chemists.
..... Click the link for more information. , which are responsible for catalyzing the thousands of chemical reactions of the living cell; keratinkeratin
, any one of a class of fibrous protein molecules that serve as structural units for various living tissues. The keratins are the major protein components of hair, wool, nails, horn, hoofs, and the quills of feathers.
..... Click the link for more information. , elastin, and collagencollagen
, any of a group of proteins found in skin, ligaments, tendons, bone and cartilage, and other connective tissue. Cells called fibroblasts form the various fibers in connective tissue in the body.
..... Click the link for more information. , which are important types of structural, or support, proteins; hemoglobinhemoglobin
, respiratory protein found in the red blood cells (erythrocytes) of all vertebrates and some invertebrates. A hemoglobin molecule is composed of a protein group, known as globin, and four heme groups, each associated with an iron atom.
..... Click the link for more information. and other gas transport proteins; ovalbumin, caseincasein
, well-defined group of proteins found in milk, constituting about 80% of the proteins in cow's milk, but only 40% in human milk. Casein is a remarkably efficient nutrient, supplying not only essential amino acids, but also some carbohydrates and the inorganic elements
..... Click the link for more information. , and other nutrient molecules; antibodiesantibody,
protein produced by the immune system (see immunity) in response to the presence in the body of antigens: foreign proteins or polysaccharides such as bacteria, bacterial toxins, viruses, or other cells or proteins.
..... Click the link for more information. , which are molecules of the immune system (see immunityimmunity,
ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian immunity.
..... Click the link for more information. ); protein hormoneshormone,
secretory substance carried from one gland or organ of the body via the bloodstream to more or less specific tissues, where it exerts some influence upon the metabolism of the target tissue.
..... Click the link for more information. , which regulate metabolismmetabolism,
sum of all biochemical processes involved in life. Two subcategories of metabolism are anabolism, the building up of complex organic molecules from simpler precursors, and catabolism, the breakdown of complex substances into simpler molecules, often accompanied by
..... Click the link for more information. ; and proteins that perform mechanical work, such as actinactin,
a protein abundantly present in many cells, especially muscle cells, that significantly contributes to the cell's structure and motility. Actin can very quickly assemble into long polymer rods called microfilaments.
..... Click the link for more information. and myosinmyosin
, one of the two major protein constituents responsible for contraction of muscle. In muscle cells myosin is arranged in long filaments called thick filaments that lie parallel to the microfilaments of actin.
..... Click the link for more information. , the contractile muscle proteins. Protein Structure Every protein molecule has a characteristic three-dimensional shape, or conformation. Fibrous proteins, such as collagen and keratin, consist of polypeptide chains arranged in roughly parallel fashion along a single linear axis, thus forming tough, usually water-insoluble, fibers or sheets. Globular proteins, e.g., many of the known enzymes, show a tightly folded structural geometry approximating the shape of an ellipsoid or sphere. Because the physiological activity of most proteins is closely linked to their three-dimensional architecture, specific terms are used to refer to different aspects of protein structure. The term primary structure denotes the precise linear sequence of amino acids that constitutes the polypeptide chain of the protein molecule. Automated techniques for amino-acid sequencing have made possible the determination of the primary structure of hundreds of proteins. The physical interaction of sequential amino-acid subunits results in a so-called secondary structure, which often can either be a twisting of the polypeptide chain approximating a linear helix (α-configuration), or a zigzag pattern (β-configuration). Most globular proteins also undergo extensive folding of the chain into a complex three-dimensional geometry designated as tertiary structure. Many globular protein molecules are easily crystallized and have been examined by X-ray diffraction, a technique that allows the visualization of the precise three-dimensional positioning of atoms in relation to each other in a crystal. The tertiary structure of several protein molecules has been determined from X-ray diffraction analysis. Two or more polypeptide chains that behave in many ways as a single structural and functional entity are said to exhibit quaternary structure. The separate chains are not linked through covalent chemical bonds but by weak forces of association. The precise three-dimensional structure of a protein molecule is referred to as its native state and appears, in almost all cases, to be required for proper biological function (especially for the enzymes). If the tertiary or quaternary structure of a protein is altered, e.g., by such physical factors as extremes of temperature, changes in pH, or variations in salt concentration, the protein is said to be denatured; it usually exhibits reduction or loss of biological activity. Protein Synthesis The cell's ability to synthesize protein is, in essence, the expression of its genetic makeup. Protein synthesis is a sequence of chemical reactions that occur in four distinct stages, i.e., activation of the amino acids that ultimately will be joined together by peptide bonds; initiation of the polypeptide chain at a cell organelle known as the ribosome; elongation of the polypeptide by stepwise addition of single amino acids to the chain; and termination of amino-acid additions and release of the completed protein from the ribosome. The information for the synthesis of specific amino-acid sequences is carried by a nucleic acid molecule called messenger RNA (see nucleic acidnucleic acid,
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of this information through protein synthesis.
..... Click the link for more information. ). Proteins are needed in the diet mainly for their amino acids, which the body uses to build new proteins (see nutritionnutrition,
study of the materials that nourish an organism and of the manner in which the separate components are used for maintenance, repair, growth, and reproduction. Nutrition is achieved in various ways by different forms of life.
..... Click the link for more information. ). The mechanism of action of many widely used antibiotics, such as streptomycinstreptomycin
, antibiotic produced by soil bacteria of the genus Streptomyces and active against both gram-positive and gram-negative bacteria (see Gram's stain), including species resistant to other antibiotics, e.g.
..... Click the link for more information. , chloramphenicolchloramphenicol
, antibiotic effective against a wide range of gram-negative and gram-positive bacteria (see Gram's stain). It was originally isolated from a species of Streptomyces bacteria.
..... Click the link for more information. , and tetracyclinetetracycline
, any of a group of antibiotics produced by bacteria of the genus Streptomyces. Effective against a wide range of Gram positive and Gram negative bacteria, tetracycline interferes with protein synthesis in these microorganisms (see Gram's stain).
..... Click the link for more information. , can be understood in terms of their ability to interfere with some stage of protein synthesis in bacteria. Protein A biological macromolecule made up of various α-amino acids that are joined by peptide bonds. A peptide bond is an amide bond formed by the reaction of an α-amino group (—NH2) of one amino acid with the carboxyl group (—COOH) of another, as shown below. Proteins generally contain from 50 to 1000 amino acid residues per polypeptide chain. See Peptide Occurrence Proteins are of importance in all biological systems, playing a wide variety of structural and functional roles. They form the primary organic basis of structures such as hair, tendons, muscle, skin, and cartilage. All of the enzymes, the catalysts in biochemical transformations, are protein in nature. Many hormones, such as insulin and growth hormone, are proteins. The substances responsible for oxygen and electron transport (hemoglobin and the cytochromes, respectively) are conjugated proteins that contain a metalloporphyrin as the prosthetic group. Chromosomes are highly complex nucleoproteins, that is, proteins conjugated with nucleic acid. Viruses are also nucleoprotein in nature. Of the more than 200 amino acids that have been discovered either in the free state or in small peptides, only 20 amino acids are present in mammalian  (1) proteins. Thus, proteins play a fundamental role in the processes of life. See Amino acids Specificity The linear arrangement of the amino acid residues in a protein is termed its sequence (primary structure). The sequence in which the different amino acids are linked in any given protein is highly specific and characteristic for that particular protein. This specificity of sequence is one of the most remarkable aspects of protein chemistry. The number of possible permutations of sequence in even so small a protein as insulin, of molecular weight 5732 and with 51 amino acid residues, is astronomic: 1051 permutations. Yet it has been established that the pancreatic cell of a given species has only one of these possible sequences. The elucidation of the mechanism conferring such a high degree of specificity on the biosynthetic reactions by which proteins are built up from free amino acids has been one of the key problems of modern biochemistry. See Molecular biology Proteins are not stretched polymers; rather, the polypeptide backbone of the molecule can fold in several ways by means of hydrogen bonds between the carbonyl oxygen and the amide nitrogen. The folding of each protein is determined by its particular sequence of amino acids. The long polypeptide chains of proteins, particularly those of the fibrous proteins, are held together in a rather well-defined configuration. The backbone is coiled in a regular fashion, forming an extended helix. As a result of this coiling, peptide bonds separated from one another by several amino acid residues are brought into close spatial approximation. The stability of the helical configuration can be attributed to hydrogen bonds between these peptide bonds. In addition to hydrogen bonds, there are electrostatic interactions, such as those between COO- and NH3+ groups of the side chains, and van der Waals forces, that is, hydrophobic interactions, which help to determine the configuration of the polypeptide chain. The term secondary structure is used to refer to all those structural features of the polypeptide chain determined by noncovalent bonding interactions. In addition to the α-helical sections of proteins, there are segments that contain β-structures in which there are hydrogen bonds between two polypeptide chains that run in parallel or antiparallel fashion. The tertiary structure (third level of folding) of a protein comes about through various interactions between different parts of the molecule. Disulfide bridges formed between cysteine residues at different locations in the molecule can stabilize parts of a three-dimensional structure by introducing a primary valence bond as a cross-link. Hydrogen bonds between different segments of the protein, hydrophobic bonds between nonpolar side chains of amino acids such a phenylalanine and leucine, and salt bridges such as those between positively charged lysyl side chains and negatively charged aspartyl side chains all contribute to the individual tertiary structure of a protein. Finally, for those proteins that contain more than one polypeptide chain per molecule, there is usually a high degree of interaction between each subunit, for example, between the α- and β-polypeptide chains of hemoglobin. This feature of the protein structure is termed its quarternary structure. Properties The properties of proteins are determined in part by their amino acid composition. As macromolecules that contain many side chains that can be protonated and unprotonated depending upon the pH of the medium, proteins are excellent buffers. The fact that the pH of blood varies only very slightly in spite of the numerous metabolic processes in which it participates is due to the very large buffering capacity of the blood proteins. Biosynthesis The processes by which proteins are synthesized biologically have become one of the central themes of molecular biology. The sequence of amino acid residues in a protein is controlled by the sequence of the DNA as expressed in messenger RNA at ribosomes. See Deoxyribonucleic acid (DNA), Ribonucleic acid (RNA), Ribosomes Degradation As with many other macromolecular components of the organism, most body proteins are in a dynamic state of synthesis and degradation (proteolysis). During proteolysis, the peptide bond that links the amino acids to each other is hydrolyzed, and free amino acids are released. The process is carried out by a diverse group of enzymes called proteases. During proteolysis, the energy invested in generation of the proteins is released. See Enzyme Distinct proteolytic mechanisms serve different physiological requirements. Proteins can be divided into extracellular and intracellular, and the two groups are degraded by two distinct mechanisms. Extracellular proteins such as the plasma immunoglobulins and albumin are degraded in a process known as receptor-mediated endocytosis. Ubiquitin-mediated proteolysis of a variety of cellular proteins plays an important role in many basic cellular processes such as the regulation of cell cycle and division, differentiation, and development; DNA repair; regulation of the immune and inflammatory responses; and biogenesis of organelles. Molecular chaperones Molecular chaperones are specialized cellular proteins that bind nonnative forms of other proteins and assist them to reach a functional conformation. The role of chaperone proteins under conditions of stress, such as heat shock, is to protect proteins by binding to misfolded conformations when they are just starting to form, preventing aggregation; then, following return of normal conditions, they allow refolding to occur. Chaperones also play essential roles in folding under normal conditions, providing kinetic assistance to the folding process, and thus improving the overall rate and extent of productive folding. Protein engineering The amino acid sequences, sizes, and three-dimensional conformations of protein molecules can be manipulated by protein engineering, in which the basic techniques of genetic engineering are used to alter the genes that encode proteins. These manipulations are used to generate proteins with novel activities or properties for specific applications, to discover structure-function relationships, and to generate biologically active minimalist proteins (containing only those sequences necessary for biological activity) that are smaller than their naturally occurring counterparts. Many subtle variations in a particular protein can be generated by making amino acid replacements at specific positions in the polypeptide sequence. For example, at any specific position an amino acid can be replaced by another to generate a mutant protein that may have different characteristics by virtue of the single replaced amino acid. Amino acids can also be deleted from a protein sequence, either individually or in groups. These proteins are referred to as deletion mutants. Deletion mutants may or may not be missing one or more functions or properties of the full, naturally occurring protein. Moreover, part or all of a protein sequence can be joined or fused to that of another protein. The resulting protein is called a hybrid or fusion protein, which generally has characteristics that combine those of each of the joined partners. protein[′prō‚tēn] (biochemistry) Any of a class of high-molecular-weight polymer compounds composed of a variety of α-amino acids joined by peptide linkages. protein any of a large group of nitrogenous compounds of high molecular weight that are essential constituents of all living organisms. They consist of one or more chains of amino acids linked by peptide bonds and are folded into a specific three-dimensional shape maintained by further chemical bonding protein
pro·tein (p), (prō'tēn, prōo'tē-in), Do not confuse this word with protean.Macromolecules consisting of long sequences of α-amino acids [H2N-CHR-COOH] in peptide (amide) linkage (elimination of H2O between the α-NH2 and α-COOH of successive residues). Protein is three fourths of the dry weight of most cell matter and is involved in structures, hormones, enzymes, muscle contraction, immunologic response, and essential life functions. The amino acids involved are generally the 20 α-amino acids (for example, glycine, l-alanine) recognized by the genetic code. Crosslinks yielding globular forms of protein are often effected through the -SH groups of two l-cysteinyl residues, as well as by noncovalent forces (hydrogen bonds, lipophilic attractions, etc.). [G. prōtos, first, + -in] protein (prō′tēn′, -tē-ĭn)n. Any of a group of complex organic macromolecules that contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur and are composed of one or more chains of amino acids. Proteins are fundamental components of all living cells and include many substances, such as enzymes, hormones, and antibodies, that are necessary for the proper functioning of an organism. They are essential in the diet of animals for the growth and repair of tissue and can be obtained from foods such as meat, fish, eggs, milk, and legumes.
pro′tein·a′ceous (prōt′n-ā′shəs, prō′tē-nā′-), pro·tein′ic (prō-tē′nĭk)(prō-tē′nəs), pro·tein′ous (prō-tē′nəs) adj.protein Biochemistry A large molecule consisting of a long chain or sequence of amino acids with a general formula of H2N–CHR–COOH–aka alpha amino acids, joined in a peptide likage; after water, proteins are the major cell constituent, and are critical for all biological structures–eg, organelles, mitochondria, enzymes and functions–eg, growth, development, immune function, motility Types Hormones, enzymes, antibodiespro·tein (prō'tēn) Macromolecules consisting of long sequences of α-amino acids [H2N-CHR-COOH] in peptide (amide) linkage (elimination of H2O between the α-NH2 and α-COOH of successive residues). Protein is three fourths of the dry weight of most cell matter and is involved in structures, hormones, enzymes, muscle contraction, immunologic response, and essential life functions. The amino acids involved are generally the 20 α-amino acids (glycine, l-alanine) recognized by the genetic code. Cross-links yielding globular forms of protein are often effected through the -SH groups of two sulfur-containing l-cysteinyl residues, as well as by noncovalent forces (e.g., hydrogen bonds, lipophilic attractions).
Compare: bioregulator[G. prōtos, first, + -in]protein a large complex molecule (M W from 10 000 to more than 1 million) built up from AMINO ACIDS joined together by PEPTIDE BONDS. All proteins contain carbon, hydrogen, oxygen and nitrogen and most contain sulphur. Proteins are produced in the cytoplasm at the ribosomes (see PROTEIN SYNTHESIS and begin as long, unbranched POLYPEPTIDE CHAINS, the primary structure. All protein molecules undergo a physical rearrangement to give a secondary structure. The most common type of shape is alpha-helix (right-handed) where the coils are held in place by hydrogen bonds. Some proteins, such as keratin, remain at this stage. An alternative secondary structure is beta-pleatingwhere parallel polypeptide chains are cross-linked by hydrogen bonds forming an extremely tough structure, as in silk. Proteins with these relatively simple two-dimensional secondary structures are called fibrous proteins. Some proteins undergo even more complex folding, where the secondary structure is arranged into a three-dimensional tertiary structure forming ‘globular’ proteins held together by forces between side groups. Such molecules are, for example, ENZYMES, ANTIBODIES, most blood proteins, and MYOGLOBIN. finally, globular proteins can be composed of two or more polypeptide chains loosely bonded together, for example, HAEMOGLOBIN, giving a quaternary structure. ProteinA substance produced by a gene that is involved in creating the traits of the human body, such as hair and eye color, or is involved in controlling the basic functions of the human body, such as control of the cell cycle.Mentioned in: Acoustic Neuroma, Gene Therapy, Phenylketonuria, Retinoblastoma, Von Willebrand Diseaseprotein Complex organic molecule composed of various combinations of any of twenty α-amino acids linked in a genetically controlled linear sequence into one or more peptide chains. Proteins are present in every living cell and form an essential constituent of cells. They are essential in many functions, such as growth and repair of tissue, transport of molecules throughout the body (e.g. haemoglobin to carry oxygen), as enzymes to catalyse biochemical reactions, immunological responses, muscle contraction (with actin and myosin), signalling (e.g. insulin which transmits a signal from a cell where it is synthesized to other cells in other tissues), or as antibodies by binding to target receptors. Many of the twenty amino acids are produced by the body. However, nine of these have to be obtained in food.pro·tein (prō'tēn) Macromolecules consisting of long sequences of α-amino acids; represents three fourths of dry weight of most cell matter; involved in structures, hormones, enzymes, muscle contraction, immunologic response, and essential life functions. [G. prōtos, first, + -in]Patient discussion about proteinQ. I get about 190 grams of protein a day. Is that too much protein? Have you ever seen a guy living only for food? No? Here I am. I get about 190 grams of protein a day. Is that too much protein? My weight is 183 pounds.A. this is a good amount, just make sure that you get the majority of it from real foods and not from powders and bars. Q. Does the cooking have a negative effect on the protein content of the food? I have heard that high temperatures cooking breaks the protein, so does the cooking have a negative effect on the protein content of the food?A. Yes. Proteins can be denatured by heat, but only when the protein structure is delicate or is exposed to extremely high temperatures for long time. You must remember that breaking of protein is the physical-chemical process where the physical or chemical structure of a protein is rearranged. So cooking will not reduce on the nutritive value of the food until it’s cooked at cooking temperatures. Q. Is it true that Casein protein can cause Cancer, or is harmful to the human body? Someone left a comment on my blog about Casein protein being bad for the body and that it could lead to Cancer. Is this true? A. I am not familiar with such information, Casein is a protein that is found in large amounts in breastmilk and milk products replacements for babies and as far as I know it has no such affect. More discussions about proteinFinancialSeeAPPPROTEIN
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protein
Related to protein: protein diet, Protein in urineWords related to proteinnoun any of a large group of nitrogenous organic compounds that are essential constituents of living cellsRelated Words- capsid
- gluten
- meat
- legume
- eggs
- egg
- milk
- amino acid
- aminoalkanoic acid
- recombinant protein
- actomyosin
- aleurone
- amyloid
- apoenzyme
- compound protein
- conjugated protein
- enzyme
- fibrin
- filaggrin
- growth factor
- haptoglobin
- iodinated protein
- iodoprotein
- nucleoprotein
- opsin
- phosphoprotein
- plasma protein
- prostate specific antigen
- PSA
- proteome
- simple protein
- polypeptide
- cytokine
- ferritin
- macromolecule
- supermolecule
- antibody
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