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Physiology of Blood

  Physiology of Blood Introduction Blood is a body fluid and is necessary for the transportation of essential nutrients and oxygen to the cells and to carry out waste products from the cells detaching it from the human body. The basic components of the blood are Red Blood Cells, White Blood Cells, Platelets and Plasma and these are the four components of the blood that are necessary for the smooth functioning of the human body. Red Blood Cells are also known as erythrocytes and are responsible for the transport of hemoglobin and in turn are responsible for the transport of oxygen from the lungs to the tissues. It is seen that in some lower animals the hemoglobin is present in the plasma as free protein and in the human being it is important for the hemoglobin to remain inside the Red Blood Corpuscles because if it will be present as free protein in the plasma than 3 % of it will leak through the capillary membrane into the tissue space or through the glomerular membrane of the kidn
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The Action of Insulin on Target Tissues

  The prompt action of insulin in the human body is the reduction of the blood glucose level and it is enhanced by the transport of glucose from the blood across the plasma membrane of the muscle and fat cells into the intracellular space. Insulin has also prompt action in converting the glycogen synthetase to an active form and it inhibits lipolysis. Because of this reason, in the peripheral tissues there is enhanced conversion of blood glucose into glycogen and lipids and an increased oxidation of glucose to carbon dioxide.             Insulin is responsible for the promotion of protein synthesis from amino acids and enhances the induction of glucokinase and phosphofructokinase and suppresses the formation of certain enzymes in gluconeogenesis such as pyruvate carboxylase and fructose diphosphatase.   Insulin appears to have generalized action on the plasma membrane of its target cells, causing it to undergo changes that leads to enhanced entry not only of glucose but also of amino
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Synthesis, Storage and Secretion of Insulin

  The information regarding synthesis, storage and secretion of Insulin was given by D.F. Steiner and his colleagues. The origin goal was to determine regarding the synthesis of A and B chains of insulin and the construction of disulfide cross linkages. The incubation of radioactive substances such as lucine and phenylalanine is done with islet tissues of rat pancreas or human pancreatic tumors and tumors of this type produce excessively large amount of insulin. Production of two radioactive proteins occurs from the pancreatic tumor and is capable of combining with a specific antibody to pure insulin. One was established to be insulin itself. The other one is closely related resembled to insulin itself because it has reacted to anti-insulin antibody and is substantially having larger molecular weight than insulin. Treatment of the second product with trypsin and carboxypeptidase causes cleavage of a number of peptide bonds and the formation of a compound that was proved to be identical
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Cytochromes

  The Cytochromes are electron-transferring proteins containing iron-porphyrin groups: they are found only in aerobic cells. Some are located in the inner mitochondria membrane, where they act sequentially to carry electrons originating from various dehydrogenase systems towards molecular oxygen. Other Cytochromes are found in the endoplasmic reticulum, where they play a role in specialized hydroxylation reactions. All Cytochromes undergo reversible Fe (II)-Fe (III) valence changes during their catalytic cycles. Their reduced forms cannot be oxidized by molecular oxygen, with the exception of the terminal cytochrome of mitochondrial respiration, namely, cytochrome a3 or cytochrome c oxidase, which also contains tightly, bound copper. In the mitochondria of higher animals, where the respiratory chain has been most thoroughly studied, at least five different cytochromes have been identified in the inner membrane: cytochrome b, c1, c, a and a3. At least, one of these, cytochrome b, occurs
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The Pathway of Electron Transport: The respiratory Chain and superoxide formation

  The concept that a chain of electron carriers is responsible for transferring electrons from substrate molecules to molecular oxygen represents the confluence of two lines of investigations. Early investigators of biological oxidations in the period 1900-1920, particularly T. Thunberg, had discovered the dehydrogenases, which catalyze removal of hydrogen atoms from different metabolites in the complete absence of oxygen . From such experiments H. Wieland later postulated that activation of hydrogen atoms is the basic process involved in biological oxidation and that molecular oxygen does not need to be activated to react with the active hydrogen atoms yielded by dehydrogenases. However, in 1913 O. Warburg discovered that cyanide in very small concentrations almost completely inhibits the oxygen consumption of respiring cells and tissues. Since, cyanide does not inhibit dehydrogenases but does form very stable complexes with iron, Warburg postulated that biological oxidation requires
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Xanthine oxidase

  In higher animals nucleotides resulting from degradation of the nucleic acids by the action of nucleases usually undergo enzymatic hydrolysis to yield, ultimately, the free purine and pyramidine bases. If not salvaged and reused, the free bases are degraded further and the end products excreted. In some vertebrates, including the primates, the Dalmatianm dog, birds, and some reptiles, the end product of purine degradation is uric acid, whereas in other mammals and reptiles, and also in mollusks, the end product is allantoin. In fishes, allantoin is broken down to allantoic acid and urea. In aquatic invertebrates ammonia is the major nitrogenous end product of purine catabolism. Curiously, guanine is the excretory form of purines in the spider and the pig.   The degradation of purines to the end product uric acid in man has been intensively studies, since genetic aberrations of this pathway are known. The major purines adenine and guanine are first converted into xanthine which is t
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Reactive Oxygen Species

Introduction The increasing concentration of oxygen level in the atmosphere near about 2.5 billion ago, oxygenic photosynthesis by cyanobacteria leads to the evolution of aerobic respiration leading to the development of complex eukaryotic organisms. All the aerobic organisms  depends upon the cellular respiration and some of the derivatives of oxygen are highly toxic for the cells. Reactive oxygen species, reactive oxygen intermediates and reactive nitrogen species have been used to define the highly reactive oxygen bearing molecules. Hydroxyl and peroxyl radicals, hydrogen peroxide and superoxide radical anions are some of the species responsible for the damage of the fatty acids, DNA and proteins as well as other cellular components. The redox reaction is typically involved in controlling production of reactive oxygen and nitrogen species. They can, in turn, react with specific functional group of target proteins like clusters, cysteines  etc. that lead to covalent protein modificat
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