Nucleic acids Health Dictionary

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Nucleic Acids: From 1 Different Sources

Substances found in all living matter that have a fundamental role in the propagation of life. Nucleic acids provide the inherited coded instructions (or “blueprint”) for an organism’s development.

There are 2 types of nucleic acid: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). In all plant and animal cells, including human cells, DNA permanently holds the coded instructions, which are translated and implemented by RNA. DNA is the main constituent of chromosomes, which are carried in the nucleus (central unit) of the cell.

DNA and RNA are similar in structure, both comprising long, chain-like molecules. However, DNA usually consists of 2 intertwined chains, whereas RNA is generally single-stranded.

The basic structure of DNA has been likened to a rope ladder, the chains forming the 2 sides, with interlinking structures in between forming the rungs.

The ladder is twisted into a spiral shape called a double helix.

Each DNA chain has a “backbone” consisting of a string of sugar and phosphate chemical groups. Attached to each sugar is a chemical called a base, which can be any of 4 types (adenine, thymine, guanine, and cytosine) and forms half a rung of the DNA ladder. The 4 bases can occur in any sequence along the chain. The sequence, which may be many millions of individual bases long, provides the code for the activities of the cell (see genetic code).

RNA is like a single strand of DNA; the main difference is that the base thymine is replaced by another base, uracil.When a cell undergoes mitotic (see mitosis) division, identical copies of its DNA must go to each of the 2 daughter cells. The 2 DNA chains separate, and 2 more chains are formed, side by side with the original chains. Because only certain base pairings are possible, the new double chains are identical to the original DNA molecule. Each of a person’s cells carries the same DNA replica that was present in the fertilized ovum, so the DNA message passes from one generation of cells to the next.

Health Source: BMA Medical Dictionary
Author: The British Medical Association

Amino Acids

Chemical compounds that are the basic building-blocks of all proteins. Each molecule consists of nitrogenous amino and acidic carboxyl groups of atoms joined to a group of carbon atoms. Polypeptides are formed by amino-acid molecules linking via peptide bonds. Many polypeptides link up in various con?gurations to form protein molecules. In humans, proteins are made up from 20 di?erent amino acids: nine of these are labelled ‘essential’ (or, as is now preferred, ‘indispensable’) amino acids because the body cannot manufacture them and is dependent on the diet for their provision. (See also INDISPENSABLE AMINO ACIDS.)... amino acids

Nucleic Acid

Group of chemicals found in cells and which carry biochemical codes for heredity and day-to-dayfunctioning of cells.... nucleic acid

Essential Fatty Acids

Three acids – arachidonic, linolenic and tinoleic – which are essential for life, but which the body cannot produce. They are found in natural vegetable and ?sh oils and their functions are varied. EFAs have a vital function in fat metabolism and transfer and they are also precursors of PROSTAGLANDINS.... essential fatty acids

Essential Amino Acids

See INDISPENSABLE AMINO ACIDS.... essential amino acids

Indispensable Amino Acids

This is the new, preferred term for essential amino acids – amino acids which are essential for the body’s normal growth and development, but which the body is unable to produce. Nine essential amino acids exist – HISTIDINE, ISOLEUCINE, LEUCINE, LYSINE, METHIONINE, PHENYLALANINE, THREONINE, TRYPTOPHAN, and VALINE – and they are present in foods rich in protein: dairy products, eggs, meat, and liver.... indispensable amino acids

Essential Fatty Acids (efa)

A group of unsaturated fatty acids essential for growth and body function. EFA activity requires three polyunsaturated fatty acids (linolenic, linoleic and arachidonic). The most essential are linoleic and arachidonic which are closely involved in metabolism, transport of fats, and maintenance of cell membranes. While linolenic and arachidonic acids can be synthesised in the body, linoleic cannot.

EFA deficiency may be caused by alcohol, particularly Omega-6. Deficiencies may be responsible for a wide range of symptoms from foul-smelling perspiration to psoriasis, pre-menstrual tension and colic. EFAs are precursors of prostaglandin formation.

EFAs are present in oily fish and reduce the adhesion of platelets and the risk of heart disease. They reduce blood cholesterol and increase HDLs.

Common sources: cold pressed seeds, pulses, nuts and nut oils. Evening Primrose oil (15-20 drops daily). The best known source is Cod Liver oil (1-8 teaspoons daily); (children 1 teaspoon daily to strengthen immune system against infection); bottled oil preferred before capsules. To increase palatability pour oil into honey jar half filled with orange or other fruit juice, shake well and drink from the jar.

Margarines, salad dressings, cooking and other refined vegetable oils inhibit complete absorption of EFAs and should be avoided. EFAs require the presence of adequate supply of Vitamins A, B, C, D, E and minerals Calcium, Iron, Magnesium and Selenium. ... essential fatty acids (efa)

Fatty Acids

Organic acids, containing carbon, hydrogen, and oxygen, that are constituents of fats and oils. There are more than 40 fatty acids, which are found in nature and which are distinguished by their constituent number of carbon and hydrogen atoms.

Certain fatty acids cannot be synthesized by the body and must be provided by the diet. These are linoleic, linolenic, and arachidonic acids, sometimes collectively termed essential fatty acids. Strictly speaking, only linoleic acid is essential, since the body can make the other 2 from linoleic acid obtained from food. (See also nutrition.)... fatty acids

Bile Acids

the organic acids in bile; mostly occurring as bile salts (sodium glycocholate and sodium taurocholate). They are cholic acid, deoxycholic acid, glycocholic acid, and taurocholic acid.

cebile-acid sequestrant a drug that binds to bile acids, forming a complex that is excreted in the faeces. Bile acids are formed in the liver from *cholesterol and the effect of loss of bile acids is a reduction in total body cholesterol and a decrease in *low-density lipoprotein serum levels. These drugs, which include *colestyramine and *colestipol, are used to treat patients with abnormally high blood cholesterol levels who are liable to develop coronary heart disease.... bile acids

Omega-3 Fatty Acids

(n-3 fatty acids) polyunsaturated fatty acids with a double bond at the third carbon atom in the chain. Omega-3 fatty acids are essential for brain development and are also associated with many health benefits, including protection against heart disease and possibly stroke and inflammatory conditions. There are three major types: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). The main source of EPA and DHA is fish oils. Vegetarians rely on EPA and DHA being synthesized by the body from dietary sources of ALA. See also essential fatty acids.... omega-3 fatty acids

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