Enzymes and Protein Isoforms – Flashcards
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| Enzyme |
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| proteins that are catalysts of biochemical reactions. |
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| Substrate |
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| reactant that binds to enzyme and is converted to product |
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| Product |
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| final molecule resulting from reaction |
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| reaction rate |
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| amount of product produced per unit of time |
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| Active site |
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| region of the enzyme where the substrate binds. |
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| Apoenzyme |
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| requires an additional non protein prosthetic group to function |
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| cofactor |
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| ions or smaller organic molecules needed for the activity of specific enzymes (non-protein) |
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| Coenzyme |
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| organic molecules derived from niacin, riboflavin and other vitamins. needed for activity of specific enzymes. (non-protein) |
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| Holoenzyme |
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| complete enyme-cofactor complex |
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| Inhibitor |
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| reduce catalytic activity of an enzyme |
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| Zymogen |
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| inactive enzyme precursor |
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| Isoenzyme |
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| structurally related protein products of different genes that catalyze the same reaction |
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| Coupled Reaction |
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| reactions that share a common intermediate |
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| Enzyme Properties |
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| Biological Catalysts High Substrate Specificity |
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| Lock and Key Theory |
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| based upon the moleculare shape of the enzyme active site and substrate. If they match, reaction will occur |
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| Induced Fit Model |
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| enzyme reacts with the substrate causing changes in the configuration of the active site, allowing them to fit together and reaction to occur |
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| Transfer (transferase) |
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| catalyzes the transfer of groups, not including hydrogen |
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| Redox (Oxidoreductase) |
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| catalyze oxidation/reduction reactions |
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| Hydrolytic (hydrolase) |
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| catalyze hydrolysis reactions |
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| Ligase |
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| catalyzes the covalent bond of two molecules coupled with the hydrolysis ATP bonds |
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| Isomerase |
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| catalyzes the interconversion of structures or geotric changes in a molecule |
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| Lyase |
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| Catalyzes the formation of double bonds |
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| Common Digestive Enzymes |
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| Amylase, lipase, bile salts, peptidases, sodium bicarbonate |
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| Amylase |
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| digests startches to disaccharides |
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| lipase |
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| further digests dietary fats into fatty acids and gylcerol |
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| bile salts |
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| involved in the emulsification process of lipid absorbtion |
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| Peptidases |
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| break specific bonds (limited proteolysis) or break down complete peptide (unlimited proteolysis) |
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| Pepsin |
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| begins digesting of proteins by hydrolyzing them to smaller polypeptides |
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| Trypsinogen |
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| converted into trypsin. digests polypeptides into smaller amino acids |
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| Sodium Bicarbonate |
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| alkaline secretion that neurailizes tummy juice as it enters the small intestine. |
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| Competitive Inhibitors |
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| directly compete with the substrate for binding with the active site |
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| noncompetitive inhibitors |
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| weakly bind to an allosteric regulatory site on the enzyme. Do not compete with substrate. |
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| Bilirubin |
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| principle pigment in bile derived from the breakdown of hemoglobin |
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| cirrhosis |
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| abnormal structure and function of the liver. caused by liver disease. |
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| excretory |
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| discharge of waste from organ |
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| secretory |
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| process by which substances are released from an organ for a particular purpose |
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| Hepatitis |
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| inflammation of the liver |
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| Jaundice |
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| yellowish staining of the skin and sclerae, caused by high levels of bilirubin |
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| NEcrosis |
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| death of living cells or tissues |
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| REticuloendothelial System (RES) |
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| cels that can take up and sequester inert particles and vital dyes, includes macrophage and precursors. |
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| Lobules |
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| hexagonal plates of cuboidal hepatic cells, microscopin functional unit of the liver |
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| Sinusoids |
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| represent the main blood supply to the liver, located between the plates of hepatic cells. |
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| Kupffer Cells |
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| phagocytic cells, line the sinusoids, remove bacteria and other foreign particles from the blood. |
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| Canaliculi |
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| interlobular bile ducts, |
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| Biliary Tract |
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| network of ducts that connect the liver, gallbladder and duodenum |
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| Hepatic Bile Duct |
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| receives bile from the canaliculi, where bile exits the liver. |
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| Cystic Ducts |
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| ducts that deliver bile from the gallbladder |
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| Common bile duct |
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| delivers bile to the duodenum which aids in digestion |
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| Portal Vein |
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| delivers blood rich in digestive end products to the liver. 2/3 of the hepatic blood supply |
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| Hepatic Artery |
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| delivers oxygen rich blood to the liver. 1/2 of the livers blood supply |
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| Hepatic Vein |
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| blood exits the liver. |
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| Functions of the liver |
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| Excretory Metabolism & Storage Detoxification Filtration |
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| Excretory Function of the Liver |
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| excretes bilirubin, cholesterol and drugs |
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| Metabolism Function of the Liver |
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| Liver metabolises and stores lipids, proteins, vitamins and minerals. |
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| Dextoxification Function of the Liver |
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| liver converts toxic and relatively insoluable compounds into less toxic compounds |
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| Filtration Function of the Liver |
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| the Kupffer cells remove bacteria and particles from the blood. |
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| FActors that Influence REaction RAtes |
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| Enzyme concentration, substrate concentration, preneces of conenzymes/cofactors, temperature, PH, inhibitors, organic solvents, salt concentration |
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| Enzyme Concentration affects reaction rate... |
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| increased products per time as enzymes increase |
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| Substrate concentration affects reaction rate... |
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| exymes works at max velocity when enzyme concentration is directly proportional to substrate concentration |
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| Temperature affects reaction rate... |
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| increasing temps usually increases reaction rate. Molecules move faster. |
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| pH affects reaction rate... |
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| other than optimal pH values, enzyme activity is affected because of structure alterations |
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| ORganic Solvents |
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| cause proteins to denture by disrupting hydrogen bonds |
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| Allosteric Enzyme |
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| has both an active site and an allosteric site to which effectors can bind. effectors binding causes the active site to change. |
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| NEgative Allosterism |
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| loss or reduction of product of the enzyme |
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| Positive allosterism |
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| additional product generated |
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| Feedback Inhibition |
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| frequently occurs in metabolic pathways. Excess final product binds to an earlier enzyme and inactivates it. |
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| Protein Modification |
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| Chemical groups are added or removed. can activate or inactivate the enzyme. Seen with phosphorylation |
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| Testing Methodology for Aspartate Aminotransferase (AST) |
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| Enzymatic Reaction. Spectrophotmetrically measured at 340 nm over time. Nad+ is directional proportional to AST |
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| Specimen requirements for AST |
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| serum, non hemolyzed, fasting, free of lipemia |
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| Testing MEthod for Alanine Aminotransferase (ALT) |
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| enzymatic reaction, spectrophotometricly measured at 340nm over time, to measure NADH which is directly proportional to ALT. |
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| Specimen Requirements for ALT |
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| Serum, fasting specimen, non hemolyzed, free of lipemia |
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| Testing Method fro Gamma-glutamyltransferase (GGT) |
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| Enzymatic Analysis. Gycerin is added, the product p-nitroaniline is measured at 405nm and 37C |
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| Speciment requirements for GGT |
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| Fasting speciment, non hemolyzed, free of lipemia, serum. |
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| Testing Method for Alkaline Phosphatase (ALP) |
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| Enzymatic analysis. The production of nitorphenoxide is spectrophotometrically measure at 405 nm. |
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| Specimen Requirements for ALP |
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| Serum, fasting, non hemolyzed, free of lipemia |
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| All Testing Methods of Bilirubin |
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| Modifed Evelyn-Malloy Method Jendrassik and Grof Method Direct Spectrophotmetry |
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| Specimen requirements for Bilirubin |
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| fasting, non hemolyzed, free of lipemia, protect from light. |
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| Modified Evely-Malloy Method |
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| Diazo reagent added to measure conjugated bilirubin at 540nm. Methanol reagent added to develop unconjugated bilirubin, total protein thein measured at 540 nm. very susceptible to hemolysis |
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| Jendrassik and Grof MEthod |
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| Most commonly used method. Sodium benzoate, followed by diazotized sulfanilic acid are incubate with the sample, then ascorbic acid, alkaline titrate, and dilute HCl are added, the resulting blue azobilirubin is measure at 600 nm. |
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| Direct Spectrophotometry (Neonatal Bilirubin) |
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| Limited to infants because of strong interference in older children and adults, measured at 454nm, then the easurement at 540nm is subtracted to account for Hb. |
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| Function of AST |
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| Catalyzes the transfer of an amino group or amino acid between aspartate and alpho-keto acids. |
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| Sources of AST |
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| Primary: Liver and heart Secondary: skeletal muscle, kidney, pancreas |
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| Clinical Significance of AST |
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| widely used in identifying necrosis and inflammation of the liver. It elevates rapidly at the beginning of the disease. |
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| Elevated EST is seen in: |
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| Chronic Hepatitis Cirrhotic Liver Muscular dystrophry, dermatomyositis, and pulmonary emboli Acute pancreatitis, crash injuries, gangrene, hemolytic disease |
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| Function of ALT |
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| catalyzes the reversile transfer of an amine group from the amino acids alanine and glutamate to alpha-ketoglutarate and pyruvate. |
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| Sources of ALT |
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| widely distributed through the body, liver is the main source, also concentrated in the kidney |
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| Clinical Significance of ALT |
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| more useful than AST in viral hepatitits and cholestatic disease, increases rapidly during hepatitis 15 to 20 times, used to screen blood donars for viral hepatitis. |
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| Function of GGT |
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| aids in the transport of amino acids through cell membranes, and involved in glutathione metabolism |
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| Sources of GGT |
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| liver and renal tubules highest activity, has been found in other places. |
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| Clinical Significance of GGT |
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| elevated in all liver diseases, highest concentration from biliary obstructions, primary or secondary liver cancers, extremely sensitive, non specific, used as a screentest for alcohol abuse. |
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| Function of ALP |
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| associated with bone calcification and lipid transport |
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| Sources of ALP |
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| Main source: Liver and Bone Secondary: Spleen, Kidney, Intestines, |
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| Clinical Significance of ALP |
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| To detect hepatobiliary disease, liver responds by synthesis of ALP, Bone disease shows the highest levels. |
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| Ammonia |
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| toxic compound, normally formed in the body from the breakdown of proteins |
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| Clinical Significance of NH3 Levels |
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| dx of Reye's syndrome, increases are caused by the liver's inability to metabolize ammonia. can cause decreased mental capacity, stupor, coma, death |
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| Bilirubin clinical significance |
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| increase can cause jaundice can also indicate Gilbert's and Grigler-Najjar syndromes |
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| Jaundice |
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| yellow discoloration of the plasma, skin, and mucous membranes caused by high concentrations of bilirubin |
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| Physiologic Jaundice |
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| Most common hyperbilirubinemia, unconjugated common in neonate, levels greater than 18-20mg can cause brain damage, also caused by hemolytic anemias. |
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| Hepatic Jaundice |
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| conjugated and unconjugated bilirubin usually due to a defect in bilirubin transport to the liver. |
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| Posthepatic Jaundice |
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| conjugated hyperbilirubinemia, impaired excretion, caused by obstruction of bile fulow to the intestines due to gallstones or tumor in the bile duct. |
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| Cirrhosis |
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| caused by excessive hepatic damage. irreversible scarring with formation of fibrotic connective tissue. Loss of functioning liver cells and impaired blood flow. |
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| Hepatitis |
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| inflammation of the liver caused by infections, radiation, drugs, chemicals or toxins |
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| Hep A |
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| transmitted by fecal-oral route by contaminated food or water. |
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| Hep B |
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| transmitted by blood, body fluids, and sexual routes. |
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| HEpatic Tumors |
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| cancers tumors from the liver, often associated with cirrhosis or Hep B |
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| Ethanol |
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| the most abused drug that affects the liver, leading cause of cirrhosis in the US |
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| Acetiminophen |
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| large doses produce fatal hepatic necrosis unles rapid treatment occurs |
