Protein | Health Dictionary

Molecular constituent of all cells comprising amino acid building blocks.
The term applies to members of a group of non-crystallisable nitrogenous substances widely distributed in the animal and vegetable kingdoms, and forming the characteristic materials of their tissues and ?uids. They are essentially combinations of AMINO ACIDS. They mostly dissolve in water and are coagulated by heat and various chemical substances. Typical examples of protein substances are white of egg and gelatin.

Proteins constitute an essential part of the diet as a source of energy, and for the replacement of protein lost in the wear and tear of daily life. Their essential constituent from this point of view is the nitrogen which they contain. To be absorbed, or digested, proteins have to be broken down into their constituent amino acids. The adult human body can maintain nitrogenous equilibrium on a mixture of eight amino acids, which are therefore known as the essential (or indispensable) amino acids. They are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. In addition, infants require histidine.



Protein | Health Dictionary

Keywords of this word: Protein


ALPHA-FETO PROTEIN

Medical Dictionary

A protein produced in the gut and liver of the FETUS. Abnormality in the fetus, such as neural tube defect, may result in raised levels of alphafeto protein in the maternal blood. In DOWN’S (DOWN) SYNDROME, levels may be abnormally low. In either case, screening of the pregnancy should be carried out, including AMNIOCENTESIS to check the amount of alpha-feto protein in the amniotic ?uid. The protein may also be produced in some abnormal tissues in the adult – in patients with liver cancer, for example.... Medical Dictionary

GLYCOPROTEINS

Medical Dictionary

Compounds comprising a PROTEIN and a CARBOHYDRATE, such as mucins, mucoid and amyloid.... Medical Dictionary

HYPOPROTEINAEMIA

Medical Dictionary

A fall in the amount of PROTEIN in the blood. This may be caused by malnutrition, loss of protein from kidney disorders, or faulty production of protein which occurs in some liver disorders. Hypoproteinaemia causes OEDEMA because ?uid accumulates in the tissues as a consequence of the metabolic abnormalities. Patients’ resistance to infections is also impaired.... Medical Dictionary

LIPOPROTEINS

Medical Dictionary

Compounds containing lipids and proteins (see LIPID; PROTEIN). Most lipids in blood PLASMA are present in this form and are characterised according to their densities: very low (VLDL), intermediate (IDL), low (LD), high (HDL) and very high (VHDL). Concentrations of lipoproteins are key factors in assessing the risk of cardiovascular disease (see HEART, DISEASES OF).... Medical Dictionary

NUCLEOPROTEIN

Herbal Medical

A molecule that is formed from a structural protein that is combined with nucleic acid, and generally found in cell nuclei and other proliferative points in cells. Upon cell death, nucleoproteins, unlike others, cannot be catabolized and recycled efficiently; instead, part of the protein is degraded to purines, and thence to uric acid. Uric acid, unlike urea, is an excretory dead end.... Herbal Medical

PROTEINURIA

Medical Dictionary

The presence of protein in the urine, sometimes a symptom of kidney compromise. See ALBUMINURIA... Medical Dictionary

PROTEINURIA

Herbal Medical

A condition in which proteins, principally ALBUMINS, are present in the URINE. It is often a symptom of serious heart or kidney disease, although some normal people have mild and transient proteinuria after exercise.

Causes

KIDNEY DISEASE is the most important cause of proteinuria, and in some cases the discovery of proteinuria may be the ?rst evidence of such disease. This is why an examination of the urine for the presence of albumin constitutes an essential part of every medical examination. Almost any form of kidney disease will cause proteinuria, but the most frequent form to do this is glomerulonephritis (see under KIDNEYS, DISEASES OF). In the subacute (or nephrotic) stage of glomerulonephritis, the most marked proteinuria of all may be found. Proteinuria is also found in infections of the kidney (pyelitis) as well as in infections of the bladder (cystitis) and of the urethra (urethritis). PREGNANCY The development of proteinuria in pregnancy requires investigation, as it may be the ?rst sign of one of the most dangerous complications of pregnancy: toxaemia of pregnancy (PRE-ECLAMPSIA and ECLAMPSIA) and glomerulonephritis. Proteinuria may also result from the contamination of urine with vaginal secretions. (See also PREGNANCY AND LABOUR.) CARDIOVASCULAR DISORDERS are commonly accompanied by proteinuria, particularly when the right side of the heart is failing. In severe cases of failure, accompanied by OEDEMA, the proteinuria may be marked. (See also HEART, DISEASES OF.) FEVER often causes proteinuria, even though there is no actual kidney disease. The proteinuria disappears soon after the temperature becomes normal. (See also PYREXIA.) DRUGS AND POISONS These include arsenic, lead, mercury, gold, copaiba, salicylic acid and quinine. ANAEMIA A trace of albumin may be found in the urine in severe anaemia.

POSTURAL OR ORTHOSTATIC ALBUMINURIA

This type is important because, if its true cause is unrecognised, it may be taken as a sign of kidney disease. The signi?cance of postural proteinuria is unclear: it is more common among young people and is absent when the person is recumbent – hence the importance of testing a urine sample that is taken before rising in the morning.

Treatment The treatment is that of the underlying disease. (See KIDNEYS, DISEASES OF.)... Herbal Medical

PURIFIED PROTEIN DERIVATIVE (PPD)

Dictionary of Tropical Medicine

Reagent used by intradermal administration in the Mantoux (tuberculin) test for TB.... Dictionary of Tropical Medicine