Tagged: Clinical case- Biochemistry for medics

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Case study- Glycosuria

A young infant, who was nourished with a synthetic formula, had a sugar in the blood and urine. This compound gave a positive reducing sugar test but was negative when measured with glucose oxidase (specific test for detection or estimation of Glucose). Treatment of blood and urine with acid (which cleaves glycosidic bonds) did not increase the amount of reducing sugar measured. Which of the following compounds is most likely to be present in this infant’s blood and urine? A. Glucose B. Fructose C. Maltose D. Sorbitol E. Lactose The right answer is fructose. Reducing sugars are usually detected by Benedict’s...

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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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Osazone test

This test is used for the identification of sugars. It involves the reaction of monosaccharide with phenyl hydrazine, a crystalline compound. All reducing sugars form osazones with excess of phenyl hydrazine when kept at boiling temperature. Each sugar has a characteristic crystal form of osazones. Which “one” of the following shapes corresponds with the shape of sucrosazone crystals? A. Needle shaped B. Petal shaped C. Rhombic plates D. Powder puff shaped E. None of the above. Details The correct answer is E- Sucrose is a non reducing sugar, it does not form osazone crystals. Upon hydrolysis, the products glucose and...

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DNA Repair

The fidelity of replication is very high, with an overall error rate of 10-9 to 10-10. Insertion of an inappropriate nucleotide that occurs during replication can be corrected by editing during the replication process. This proof reading function is performed by a 3′-5′ exonuclease activity associated with the polymerase complex. The post replication repair process also increases the fidelity of replication. Which “one” of the following is not a post replication DNA repair mechanism? A. 5′-3′ – Exonuclease repair B. Base excision repair C. Mismatch repair D. Nucleotide excision repair E. Direct repair The answer is- A – 5′-3′ – Exonuclease repair....

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Restriction enzymes and DNA fingerprinting

DNA fingerprinting is used in the legal world to determine parentage, genealogy, or other genetic relationships, or to implicate suspects in law enforcement investigations involving violent crimes. Fragments produced by various restriction enzymes from a number of different loci can be used to identify individuals with the accuracy of a fingerprint. Therefore, this technique is called “Fingerprinting”. Which “one” of the following statements is incorrect about restriction enzymes? A. They are site specific endonucleases B.  The restriction sites are palindrome in nature C. All restriction enzymes are of bacterial origin D. They always produce complementary single stranded overhangs E. They...

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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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Pitocin – a synthetic form of Oxytocin

Pitocin is a synthetic form of Oxytocin that can be administered during labor to initiate uterine contractions or augment labor in the event of the failure of the normal progression of labor. Chemically Oxytocin is a: A. Glycoprotein B. Glycolipid C. Peptide D. Nucleoprotein E. Lipoprotein. The correct answer is C- Peptide Peptides are short polymers of amino acids. Physiologically they perform prominent roles  in the neuroendocrine system as hormones, hormone-releasing factors, neuromodulators, or neurotransmitters. Clinically some of the peptides are used as antibiotics, anticancer drugs and some in toxic dosage promote tumor formation. Summary of biologically important peptides (Alphabetically)...

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Chemical nature of sialic acid- Question of the day.

The influenza virus infects cells by binding its viral hemagglutinin to “Sialic acid” on the surface of epithelial cells. Which of the following represents the true chemical nature of sialic acid? A. Glycolipid B. Amino sugar C. Amino sugar acid D. Lipoprotein E. Glycoprotein. Details The correct answer is C- Amino sugar acid. Sialic acid is a sugar derivative. Basic concept Amino sugars Amino groups may be substituted for hydroxyl group of sugars to give rise to amino sugars. Generally, the amino group is added to the second carbon of the hexoses. The most common amino sugars are Glucosamine and...

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Aromatase inhibitor acting by increasing km value

Case details An 8-year-old girl presents with precocious puberty, short stature, and coffee-colored macules. The patient has been diagnosed with McCune-Albright syndrome that results from estrogen production due to excessive Aromatase activity from ovarian follicular cysts. To treat the precocious puberty and other symptoms, the patient has been prescribed with a drug that inhibits the Aromatase activity. The drug is known to act by binding to substrate binding site, producing an increase in km. Which of the following choices best describes the mechanism of inhibition of the drug? A. Competitive B. Non Competitive C. Allosteric D. Suicidal E. Feedback inhibition...

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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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Case study- Glycogen storage disease

Case details A female infant appeared normal at birth but developed signs of liver disease and muscular weakness at 3 months. She had periods of hypoglycemia, particularly on awakening. Examination revealed an enlarged liver. Laboratory analyses following fasting revealed ketoacidosis, blood pH 7.25, and elevations in both alanine transaminase (ALT) and aspartate transaminase (AST). Administration of glucagon following a carbohydrate meal elicited a normal rise in blood glucose, but glucose levels did not rise when glucagon was administered following an overnight fast. Liver biopsy revealed an increase in the glycogen content (6 percent of wet weight). In which of the...

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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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Excessive Nasogastric (NG) drainage and acid base status

Case details A postoperative surgical patient had a nasogastric tube (figure) in for three days.   Figure- Nasogastric tube   The nurse caring for the patient stated that there was much drainage from the tube that is why she felt so sick. What could be the reason? A. Metabolic Acidosis B. Metabolic Alkalosis C. Respiratory Acidosis D. Respiratory Alkalosis E. None of the above. The correct answer is- B-Metabolic alkalosis. Metabolic alkalosis is primary increase in HCO3 − with or without compensatory increase in PCO2; pH may be high or nearly normal. Whenever a hydrogen ion is excreted, a bicarbonate ion is gained into the extracellular...

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Breathing difficulty- What is the acid- base imbalance?

Case details An 80-year-old man had a bad cold. After two weeks he said, “It went in to my chest; I am feeling tightness in my chest, I am coughing, suffocated and unable to breathe!” (Figure) Figure- The gaseous exchange is impaired in pulmonary diseases What could be the possible reason? A. Metabolic Acidosis B. Metabolic Alkalosis C. Respiratory Acidosis D. Respiratory Alkalosis E. None of the above. Answer- C- Respiratory acidosis is the correct answer. Respiratory acidosis is CO2 accumulation (hypercapnia) from a decrease in respiratory rate, respiratory volume (hypoventilation), or both. It can be due to severe pulmonary...

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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 Insulin in Diabetic ketoacidosis

Case details An 8-year old boy, a known diabetic (type 1 DM), has been brought to emergency room in a state of coma. His breathing is rapid and deep, and his breath has a fruity odor. His blood glucose is 480 mg/dL. The attending physician has administered IV fluids, insulin, and potassium chloride. A rapid effect of insulin in this situation is to stimulate A. Gluconeogenesis in liver B. Fatty acid release from adipose C. Glucose transport in muscle D. Ketone utilization in the brain E. Glycogenolysis in the liver Answer- The right answer is- c) Glucose transport in muscle....

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Case study- Achlorhydria (Discussion)

A 65- year-old woman is evaluated by a gastroenterologist for progressive signs and symptoms of malnutrition. Throughout her work up, she is found to have significantly decreased stomach acid. She is also found to have antibodies to gastric parietal cells, which are normally responsible for the production of acid. Why is hydrochloric acid important in digestion? A. It stimulates the cleavage of trypsinogen to trypsin B. It is required for the activity of α- Amylase C. It converts pepsinogen to pepsin D. It is required for lipid digestion E. It drives the secondary transport of amino acids Answer- The correct...

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Case study- Pellagra

QUESTION OF THE DAY A 56 – year-old male on Isoniazid therapy for tuberculosis has developed rashes on the exposed parts of the body. History is also suggestive of disoriented memory and diarrhea. The patient has been diagnosed with pellagra. Pellagra is known to manifest in individuals deficient of niacin. What is the correlation of Isoniazid therapy and niacin deficiency? A. Isoniazid inhibits biological activation of niacin B. Isoniazid prevents absorption of niacin C. Isoniazid promotes excessive excretion of niacin D. Isoniazid inhibits endogenous synthesis of niacin E. Isoniazid acts a competitive inhibitor of niacin Answer- D- Isoniazid inhibits the...

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