n. a pentose sugar (i.e. one with free carbon atoms) that is a component of *RNA and several coenzymes. Ribose is also involved in intracellular metabolism.
Genes carry, in coded form, the detailed speci?cations for the thousands of kinds of protein molecules required by the cell for its existence, for its enzymes, for its repair work and for its reproduction. These proteins are synthesised from the 20 natural AMINO ACIDS, which are uniform throughout nature and which exist in the cell cytoplasm as part of the metabolic pool. The protein molecule consists of amino acids joined end to end to form long polypeptide chains. An average chain contains 100–300 amino acids. The sequence of bases in the nucleic acid chain of the gene corresponds in some fundamental way to the sequence of amino acids in the protein molecule, and hence it determines the structure of the particular protein. This is the genetic code. Deoxyribonucleic acid (see DNA) is the bearer of this genetic information.
DNA has a long backbone made up of repeating groups of phosphate and sugar deoxyribose. To this backbone, four bases are attached as side groups at regular intervals. These four bases are the four letters used to spell out the genetic message: they are adenine, thymine, guanine and cystosine. The molecule of the DNA is made up of two chains coiled round a common axis to form what is called a double helix. The two chains are held together by hydrogen bonds between pairs of bases. Since adenine only pairs with thymine, and guanine only with cystosine, the sequences of bases in one chain ?xes the sequence in the other. Several hundred bases would be contained in the length of DNA of a typical gene. If the message of the DNA-based sequences is a continuous succession of thymine, the RIBOSOME will link together a series of the amino acid, phenylalanine. If the base sequence is a succession of cytosine, the ribosome will link up a series of prolines. Thus, each amino acid has its own particular code of bases. In fact, each amino acid is coded by a word consisting of three adjacent bases. In addition to carrying genetic information, DNA is able to synthesise or replicate itself and so pass its information on to daughter cells.
All DNA is part of the chromosome and so remains con?ned to the nucleus of the cell (except in the mitochondrial DNA). Proteins are synthesised by the ribosomes which are in the cytoplasm. DNA achieves control over pro-tein production in the cytoplasm by directing the synthesis of ribonucleic acid (see RNA). Most of the DNA in a cell is inactive, otherwise the cell would synthesise simultaneously every protein that the individual was capable of forming. When part of the DNA structure becomes ‘active’, it acts as a template for the ribonucleic acid, which itself acts as a template for protein synthesis when it becomes attached to the ribosome.
Ribonucleic acid exists in three forms. First ‘messenger RNA’ carries the necessary ‘message’ for the synthesis of a speci?c protein, from the nucleus to the ribosome. Second, ‘transfer RNA’ collects the individual amino acids which exist in the cytoplasm as part of the metabolic pool and carries them to the ribosome. Third, there is RNA in the ribosome itself. RNA has a similar structure to DNA but the sugar is ribose instead of deoxyribose and uracil replaces the base thymine. Before the ribosome can produce the proteins, the amino acids must be lined up in the correct order on the messenger RNA template. This alignment is carried out by transfer RNA, of which there is a speci?c form for each individual amino acid. Transfer RNA can not only recognise its speci?c amino acid, but also identify the position it is required to occupy on the messenger RNA template. This is because each transfer RNA has its own sequence of bases and recognises its site on the messenger RNA by pairing bases with it. The ribosome then travels along the chain of messenger RNA and links the amino acids, which have thus been arranged in the requisite order, by peptide bonds and protein is released.
Proteins are important for two main reasons. First, all the enzymes of living cells are made of protein. One gene is responsible for one enzyme. Genes thus control all the biochemical processes of the body and are responsible for the inborn di?erence between human beings. Second, proteins also ful?l a structural role in the cell, so that genes controlling the synthesis of structural proteins are responsible for morphological di?erences between human beings.... genetic code
Habitat: Cultivated in Punjab and Rajasthan.
English: Date Palm.Ayurvedic: Kharjuura, Kharjuuraka, Kharjuurikaa. Pindakharjuurikaa. Chhuhaaraa (dry date). Pindakhar- juura is the fruit of Phoenix acaulis Roxb.Unani: Khurmaa, Khajuur, Chhuharaa.Siddha/Tamil: Perichchankay, Ita.Action: Fruit pulp—antitussive, expectorant, demulcent, laxative, diuretic, restorative. Sap—cooling, laxative. Gum—used in diarrhoea and genitourinary diseases.
The fruit contains ascorbic acid (vitamin C), carotene (as vitamin A), nicotinic acid, riboflavin, thiamine, sugars (60-80%). Besides sucrose and invert sugars, rhamnose, xylose, ara- binose, ribose, galactose and galac- turonic acid have been identified in the fruit. Invert sugar predominates in the soft dates; sucrose in dry varieties. The dried date, used in Ayurvedic and Unani compositions, contains protein 2.5-3, fat 0.5, carbohydrates 75.882.9% and calcium 35.9, phosphorus 129.3 and iron 3.4 mg/100 g. Presence of sterols of ergosterol group, and esterone has been reported from dried date seeds.Charged C-glycosylflavones and caf- feylshikimic acid, leucocyanidin are characteristically present in the plant. Flavonol glycosides are also common. Several uncharged C-glycosylflavones were also detected.Dosage: Fresh fruit—10-50 g, dried fruit—10-15 g. (API, Vol. IV.)... phoenix dactyliferaHabitat: Sub-alpine Himalayas, from Kashmir to Sikkim at altitudes of 3,300-5,200 m.; also cultivated in Assam.
English: Indian Rhubarb, Himalayan Rhubarb.Ayurvedic: Amlaparni, Pitamuuli, Gandhini Revatikaa. Revandachini (roots).Unani: Revandchini.Siddha/Tamil: Revalchinikattai, Nattirevaichini.Action: Purgative, astringent, aperient. Used for constipation and atonic dyspepsia. Not advised for patients suffering from gout, rheumatism, epilepsy. (When given internally, the root imparts a deep tinge to the urine.)
The root gave emodin, emodin- 3-monomethyl ether, chrysophanol, aloe-emodin, rhein. These occur free and as quinone, anthrone or dianthrone glycosides. The astringent principle consists of gallic acid together with small amounts of tannin. The drug also contain cinnamic and rhe- inolic acids, volatile oil, starch and calcium oxalate. Two major glyco- sidic active principles, sennoside A and B, are present along with free an- thraquinones.At low doses, the tannin exerts astringent effect and relieves diarrhoea; at higher doses anthraquinones stimulate laxative effect and relieve constipation. (Natural Medicines Comprehensive Database, 2007.)There are three main types of rhubarbs—Chinese, Indian or Himalayan, and Rhapontic.The Chinese rhubarb consists of the rhizomes and roots of Rheum palma- tum and R. officinale.The Indian rhubarb consists of dried rhizomes of R. emodi and R. web- bianum; rhizomes and roots of R. moorcroftianum and R. spiciforme are also reported to be mixed with the drug. R. rhaponticum is the Rhapontic rhubarb.Rheum moorcroftianum Royle (the Himalayas at altitudes of 3,0005,200 m., chiefly in Garhwal and Ku- maon) possesses properties similar to those of R. emodi and the roots are mixed with the latter.Rheum spiciforme Royle (drier ranges of Kumaon and Sikkim at altitudes of 2,700-4,800 m.) also possesses purgative properties. The rhizomes and roots are mixed up with Himalayan rhubarb.Rheum webbianum Royle (the western and central Himalayas at altitudes of 3,000-5,000 m.) is the source of Himalayan rhubarb.Rheum palmatum is esteemed as the best type of (Chinese) rhubarb. Two new stilbene glycosides, 4'-O- methylpiceid and rhapontin, isolated from the roots, exhibited moderate alpha-glucosidase inhibitory activity. Anthraquinone glucoside, pul- matin, isolated from the roots, along with its congeners, chrysophanein and physcionin, showed cytotoxic activity against several types of carcinoma cells. Polysaccharides, isolated from the roots and rhizomes, contained lyx- ose, glucose, galactose, xylose, rham- nose, mannose and ribose.Dosage: Root—0.2-1.0 g powder. (CCRAS.)... rheum emodiHabitat: Aka hills in Arunachal Pradesh.
Ayurvedic: Vaaraahikanda (substitute), Vaaraahi. (Dioscorea bulbifera is equated with Vaaraahikanda.)Folk: Duukarkand (Gujarat).Action: Tuber—nutritive and digestive; applied to haemorrhagic diathesis, cachexia, leprosy and other cutaneous affections.
The tuber contains gamma-amino- butyric acid, glycine, leucine, valine, quercetin-3-arabinoside, D (-)-ribose, n-triacontanol, betulinic acid, castano- genin and taccalin.Habitat: Entire Deccan Peninsula, extending into Madhya Pradesh and Bihar.
English: Fiji Arrowroot, Tahiti Arrowroot.Ayurvedic: Suurana. (Instead of wild var., cultivated elephant-foot- yam, Amorphophallus paeoniifolius var. campanulatus, is used.)Siddha/Tamil: Karachunai.Action: Tuber—acrid, astringent, carminative, anthelmintic. Used in the treatment of piles, haemophilic conditions, internal abscesses, colic, enlargement of spleen, vomiting, asthma, bronchitis, elephantiasis and intestinal worms.
The tuber, macerated and repeatedly washed with water, yield a starch (76.0%).The presence ofbeta-sitosterol, ceryl alcohol and taccalin (a bitter principle) has been reported in the tuber.Taccagenin and leontogenin have been isolated froma acid hydrolysate of leaf extract. Diosgenin and its derivatives, isonarthogenin and isonu- atigenin together with nuatigenin have also been isolated.A bitter extract, prepared by washing the grated tubers in running water, is a rubefacient; and is also given in diarrhoea and dysentery.... tacca aspera
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