Tagged: Namrata

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An amino acid that acts as a component of histones and a precursor for Nitric oxide (NO)

The general structure of chromatin has been found to be remarkably similar in the cells of all eukaryotes. The most abundant proteins associated with eukaryotic DNA (somewhat more than half its mass) are histones, a family of basic proteins rich in the positively charged amino acids that interact with the negatively charged phosphate groups in DNA. Which of the following amino acids acts as a component of histones and a precursor for Nitric oxide (NO)? A. Arginine B. Histidine C. Lysine D. Asparagine E. Leucine The correct answer is- A- Arginine. Histones are nucleoproteins, rich in basic amino acids such...

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Histidine to histamine conversion

Histamine causes vasodilatation and bronchoconstriction. In the stomach it stimulates the secretion of hydrochloric acid (HCl). Histamine binds to H1 receptors in the stomach, stimulating the release of gastric acid. Pharmacological blockers of H1 receptors are used in the treatment of gastric reflux. H2 receptors are located on basophils; histamine stimulates their degranulation during the allergic responses. H2 receptor blockers are used to treat allergic conditions. Histamine is produced from Histidine by: A. Deamination B. Transamination C. Carboxylation D. Decarboxylation E. Methylation The correct answer is D- Decarboxylation. Histamine is a biogenic amine. A biogenic amine is a potent signaling...

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Free radical injury and antioxidants

The organic solvent Carbon tetra chloride (CCl4) is used in the dry cleaning industry. The Carbon tetra chloride (CCl4) is metabolized in the body by cytochrome P450 enzyme system to form a free radical species CCl3– . This highly reactive species causes a chain reaction of lipid peroxidation, particularly in the liver, that can lead to hepatocellular necrosis. The cells have developed enzymes and other molecules to help them protect against the free radical damage. Some dietary components also act as anti-oxidants. Which of the following dietary components can provide some protection against free radical injury? A. Glutamine B. Linoleic...

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Cholesterol content and membrane fluidity

Membrane fluidity is required for the proper movement of erythrocytes through capillaries of the spleen. Patients with spur cell anemia have increased cholesterol content (> 40%) in the membranes of their erythrocytes, resulting in decreased membrane fluidity. Thus, erythrocytes from these patients are destroyed in the spleen. Which of the following statements is incorrect concerning the significance of cholesterol? A. Elevated levels of cholesterol are associated with atherosclerosis. B. The serum total cholesterol content should be less than 200 mg/dl. C. Cholesterol is a major component of gall stones. D. Excess cholesterol is excreted from the liver in the bile...

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Prokaryotes versus Eukaryotes

Case details A young man was brought to the emergency room after being hit by a car. His leg bone was broken in half, and the bone was protruding through the skin. He was recovering well after the orthopedic surgery. After several days he developed wound infection. The wound culture revealed a new bacterial organism that was resistant to all available antibiotics. The drugs acting as antibiotics specifically inhibit bacterial proliferation by inhibiting any of the processes such as replication, transcription or translation. Which of the following statements is exclusively true of prokaryotes but not of eukaryotes? A. Most of...

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Nonessential in normal health but essential during conditions of enhanced growth or surgical recovery

Case details An 8-year-old child requires surgical intervention and substantial recovery time in the hospital. A nutritionist recommends a specific dietary plan. The plan includes a protein rich diet with the special supplementation of an amino acid that is typically considered a nonessential, but becomes an essential amino acid under conditions of enhanced growth or surgical recovery. Which of the following amino acids should be considered in this dietary plan? A. Alanine B. Arginine C. Glycine D. Serine E. Tyrosine The correct answer is Arginine. Arginine is a semi essential amino acid. It can be synthesized in the human body...

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RNA splicing

Case details A 45-year- old female of Indian origin reported for a routine checkup. She had no complaints and was in good health; however she reported a family history of anemia. Her complete blood count demonstrated mild anemia and the attending physician suspected thalassemia minor in the patient. Thalassemia is most often due to a defect in RNA splicing, which is best explained by which of the following statements? A) A high molecular weight precursor is trimmed to a short and mature m RNA. B) The coding regions found on the introns are rearranged and joined together. C) The introns...

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Vitamin deficiency in cystic fibrosis

Case details A 30-month-old female child whose growth rate has been in the lower 10th percentile over the last year presents with chronic, nonproductive cough and diarrhea with foul-smelling stools. She is diagnosed as having cystic fibrosis (figure-1). For which of the following vitamins is this child most likely to be at risk of deficiency? A. Ascorbic acid (vitamin C) B. Biotin C. Folic acid D. Retinol (vitamin A) E. Riboflavin (vitamin B2) Answer- D. Because cystic fibrosis leads to pancreatic damage and diminution of the ability to secrete HCO3 ions and pancreatic digestive enzymes with the result that fat...

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Role of ACAT in the esterification of cholesterol

See the image below and note the role of ACAT (Acyl Co A cholesterol acyl transferase) in the esterification of cholesterol. Cholesterol is stored in the cell in the form of cholesteryl esters. Esterification involves the coupling of cholesterol with a fatty acid, generally this fatty acid is a- A. Saturated fatty acid B. Monounsaturated fatty acid C. Polyunsaturated fatty acid D. Dienoic acid E. Any of the above. Figure-1- Uptake of LDL and fate of cholesterol The correct answer is- Monounsaturated fatty acid, Commonly Oleic acid is used for the esterification (figure-2) Oleic acid is a mono- unsaturated fatty...

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