Tagged: Clinical cases- Biochemistry for medics

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Hydroxyurea in the treatment of Leukemia

Case details A physician evaluates a 32-year-old patient for fatigue. The patient is found to have an elevated white blood cell count and an enlarged spleen. A referral to an oncologist results in a diagnosis of chronic myelogenous leukemia. Treatment with hydroxyurea, a ribonucleotide reductase inhibitor is begun. The normal functioning of this enzyme is to do which of the following? A. Converts xanthine to uric acid B. Converts ribonucleotides to deoxyribonucleotides C. Degrades guanine to xanthine D. Degrades AMP to IMP E. Converts PRPP to phosphoribosylamine   The correct answer is- B- Converts ribonucleotides to deoxyribonucleotides. Either hydroxyurea or...

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Components of Sucrose

A 7-month-old baby girl, the second child born to unrelated parents was brought to Pediatrics outdoor department. History revealed that she did not respond well to breast-feeding and was changed entirely to a formula based on cow’s milk at 4 weeks. Between 7 and 12 weeks of age, she was admitted to the hospital twice with a history of screaming after feeding, but was discharged after observation without a specific diagnosis. Elimination of cow’s milk from her diet did not relieve her symptoms; her mother reported that the screaming bouts were worse after the child drank juice and that she...

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Cloning

A clone is a population of identical organisms derived from a single parental organism. In Molecular biology- A clone is a collection of molecules or cells, all identical to an original molecule or cell. If the original cells harbored a recombinant DNA molecule in the form of a plasmid, the plasmids within the millions of cells in a bacterial colony represent a clone of original DNA molecules; these molecules can be isolated and studied. The mechanism of cloning involves , i) Cutting DNA at precise locations, ii) Joining two DNA fragments covalently, iii) Selection of a small molecule of DNA...

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Splicing

The most common cause of β- Thalassemia is the defect in mRNA splicing of the beta globin gene. Mutations that affect the splicing create aberrant transcripts that are degraded before they are translated. If patients inherit a single mutated gene (thalassemia minor), the disease manifests with a mild anemia. However, patients with homozygous mutations (thalassemia major) have severe transfusion-dependent anemia. Which of the following types of RNA are involved in the splicing process? A. Ribosomal RNA (r RNA) B. Small nuclear RNA (sn RNA) C. Transfer RNA (t RNA) D. Small cytoplasmic RNA (sc RNA) E. Heterogeneous nuclear RNA (hn...

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Cholesterol transport and Tangier disease

Tangier disease is a disease of cholesterol transport. The first case was identified in a patient who lived on the island of Tangier and who had characteristic orange-colored tonsils, a very low HDL level, and an enlarged liver and spleen. Due to a mutation in the transport protein the cholesterol cannot properly exit the cell to bind to apo A (that forms HDL). This results in a very low HDL levels. Cholesterol obtained by HDL from cell membranes is converted to cholesterol esters. Which of the following enzymes catalyzes the esterification of cholesterol? A. HMG Co A reductase B. Lecithin:...

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Energy output per Acetyl co A by one round of TCA cycle

The total energy generated by one round of TCA cycle starting with 1 Acetyl co A is approximately 12 ATP. Of this total energy output, what percentage is contributed by oxidation of niacin dependent coenzymes in the electron transport chain? A. 38% B. 42% C. 86% D.75 % E. 100% The correct answer is D- 75%. The citric acid cycle (Krebs cycle, tricarboxylic acid cycle) includes a series of oxidation-reduction reactions in mitochondria that result in the oxidation of an acetyl group to two molecules of carbon dioxide and reduce the coenzymes that are reoxidized through the electron transport chain,...

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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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Significance of Glycine

Glycine functions as an inhibitory neurotransmitter in the brain stem and the spinal cord. Its actions are antagonized by the rodenticide Strychnine, leading to twitching and muscle spasm. The non availability of glycine can affect the synthesis of which of the following compounds? A. Methionine B. Hippuric acid C. Glucuronic acid D. Cysteine E. Mercapturic acid. Details The correct answer is- B- Hippuric acid Aromatic compounds like benzoic acid obtained from diet are detoxified by conjugation with glycine to form Hippuric acid (figure-1) which is excreted in urine.  This reaction takes place exclusively in liver. Hippuric acid excretion test is...

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Question of the day-Enzyme catalyzing Carbon-Carbon bond cleavage in Glycolysis

Which of the following enzymes cleaves a carbon-carbon bond in glycolysis? A. Phospho triose isomerase B. Aldolase C. Phospho glycerate kinase D. Enolase E. Pyruvate Kinase The correct answer is B- Aldolase. The Aldolase cleaves fructose-1,6-bisphosphate (the product of 2nd glycolytic reaction catalyzed by Phospho fructo kinase -1) between the C-3 and C-4 carbons to yield two triose phosphates. The products are dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (figure). Figure- Reactions of glycolysis. Phospho triose isomerase Of the two products of the Aldolase reaction, only glyceraldehyde-3-phosphate goes directly into the second phase of glycolysis. The other triose phosphate, dihydroxyacetone phosphate, must be...

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Role of “Nucleoside analogs” in HIV infection

Case details A 34-year-old homosexual man has recently been diagnosed with HIV (human immunodeficiency virus) infection. His CD4+ T-cell count has dramatically decreased, and he has a high viral load. He has been referred to an infectious disease clinic where he has been prescribed with a nucleoside analog. The nucleoside analogs inhibit DNA synthesis. Which of the following chemical groups essentially required for DNA polymerization is absent in the nucleoside analogs? A. 5′ Phosphate B. 3′ Hydroxyl C. 2′ Methyl D. 3′-Phosphate E. 5′ Hydroxyl. The correct answer is- B-3′ Hydroxyl. Basic concept Nucleosides Nucleosides are derivatives of purines and pyrimidines...

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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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Elevated Acylcarnitine compounds and associated hypoglycemia- What is the defect?

Case details A 5- year-old boy suffered gastroenteritis for two days and was brought to emergency in the semiconscious state. Blood glucose at the time of admission was 45 mg/dl and his urine was negative for glucose and ketone bodies. Glucose was administered intravenously and his condition improved within 10 minutes. Subsequent laboratory investigations revealed elevated acylcarnitine residues. The child was diagnosed with an enzyme deficiency. The parents were instructed to feed the child more frequently. Which of the following enzymes might be deficient? A. Acyl Co A synthetase B. Carnitine Acyl transferase-1 C. Translocase D. Carnitine Acyl transferase-2 E....

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Diabetic ketoacidosis- Enzyme for ketones formation?

Case details A 54- year-old man with Type 1 diabetes is referred to an ophthalmologist for evaluation of developing cataract. Blood chemistry results are shown below- Fasting blood glucose   198 mg/dl Hemoglobin A                  15 gm/dl Hemoglobin A 1c             10% of total Hb Urine ketones                   Positive Urine glucose                    Positive Which of the following enzymes is most strongly associated with ketones formation in this patient? A) Pyruvate dehydrogenase complex B) Thioesterase C) Thiophorase D) Thiokinase E) Thiolase. The correct answer is- E- Thiolase. Out of the given options thiolase is the only enzyme involved in the ketogenesis. The process of ketogenesis starts from...

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Alcohol induced hypoglycemia

Case details A known alcoholic is found lying semiconscious at the bottom of a stairwell with a broken arm by his landlady, who called an ambulance to take him to the emergency room. Initial laboratory studies showed are relatively large anion gap of 34 (normal = 9 to 15). His blood alcohol was elevated at 245 mg/dL (intoxication level = 150 to 300 mg/dL), and his blood glucose was 38 mg/dL (low normal). The patient/s large anion gap and hypoglycemia can best be explained by which of the following? A. Decreased secretion of glucagon B. Increased secretion of insulin C....

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Protein folding defect

Case details A 50-year-old male presents with “dancing –like” movements of his arms and progressive dementia. He cannot control the movement of his arms. He states that he knows that he has Huntington’s disease because his mother has the same disease. The disease is caused by abnormal protein folding. Which of the following helps to mediate proper protein folding? A. Chaperones B. Transcription factors C. DNA binding proteins D. RNA binding proteins E. All of the above.   Figure-Folding of a protein to acquire a mature functional conformation Discussion- The correct answer is Chaperones. Most proteins must fold into defined three-dimensional...

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Implications of maternal hyperglycemia

Case details A pregnant mother with a history of long-standing uncontrolled diabetes mellitus has come for a routine check up. The examination reveals a normal pregnancy. Blood chemistry reveals random blood glucose – 165 mg/dl and Glycated hemoglobin (HbA1c) of 10.5 %. What are the possible complications in a fetus under such conditions of maternal hyperglycemia? A. Fetal hyperglycemia B. Large fetal size C. Hypoglycemia after birth D. Fetal hyperinsulinemia E. All of the above. See the image below and try to find out the answer Figure- Showing the implications of maternal hyperglycemia. The correct answer – E- all of the...

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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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Case study- Hyperammonemia

Question of the day -Hyperammonemia A new-born becomes progressively lethargic after feeding. His respiratory rate increases and he becomes virtually comatose, responding only to painful stimuli, and exhibits mild respiratory alkalosis. Suspicion of a urea cycle disorder is aroused and evaluation of serum amino acid levels is initiated. In the presence of hyperammonemia, production of which of the following amino acids is always increased? A. Glycine B. Arginine C. Proline D. Histidine E. Glutamine Answer- The correct answer is Glutamine. Urea cycle disorder results in reduced ammonia disposal and hence the patients present with symptoms of hyperammonemia. Ammonia is detoxified by...

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A common intermediate of Urea and TCA cycle

Question of the day Which one of the following can be converted to an intermediate of either the citric acid cycle or urea cycle? A. Tyrosine B. Lysine C. Leucine D. Tryptophan E. Aspartate Answer- The correct answer is- E -Aspartate. 1) Role of Aspartate in urea cycle Aspartate participates in urea cycle for condensation with citrulline to form Argino succinic acid. The reaction is catalyzed by Argino succinic acid synthetase (Aspartate provides one out of the two nitrogens of urea, the other nitrogen is contributed by Glutamate). In the subsequent reaction, Argino succinic acid undergoes a lytic reaction to...

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Immediate treatment of Acute MI

Case details A 56-year-old man with hypercholesterolemia was rushed to the hospital with crushing chest pain radiating to his left arm and a probable heart attack. Which of the following treatments should be considered? A. A platelet transfusion B. Heparin transfusion C. Thrombin transfusion D. Fibrinogen infusion E. Tissue plasminogen activator infusion The correct answer is- E- Tissue plasminogen activator infusion. Tissue plasminogen activator (tPA) causes activation of plasminogen (zymogen form) to plasmin (active form). Plasmin hydrolyzes fibrin to form soluble degradation products (Figure-1). Figure-1- Mechanism of action of tPA The main goals of medical therapy of acute myocardial infarction...

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Action of Alpha- Amylase on starch

Prior to a race, many marathon runners will try to increase their glycogen concentrations by loading up with foods with high starch content, such as pasta. α-Amylase secreted by the pancreas will digest the starch into which of the following major products? A. Amylose, amylopectin, and maltose B. Glucose, galactose, and fructose C. Glucose, sucrose, and maltotriose D. Limit dextrins, maltose, and maltotriose E. Limit dextrins, lactose, and sucrose   Answer- The correct answer is-D- Limit dextrins, maltose, and maltotriose Starch consists of two fractions. About 20% is a water soluble material called Amylose. The majority of the starch is...

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Prolonged fasting and gluconeogenesis…

A 14-year-old high school girl who is extremely conscious about her appearance has gone a full day fasting to fit in to a dress she intentionally brought a size smaller than her actual size for a dance party. Which of the following organs/tissues contribute to the glucose that is being synthesized through gluconeogenesis during periods of prolonged fasting? A. Spleen B. Red blood cells C. Skeletal muscle D. Liver E. Brain D-Liver is the correct answer. Gluconeogenesis is the process of converting noncarbohydrate precursors to glucose or glycogen. The major substrates are the glucogenic amino acids, lactate, glycerol, and propionate....

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Significance of Lipoproteins

Case details A 50 -year-old male presents with weakness in his left leg. History reveals that he is a known hypertensive and a diabetic from the past 5 years, but is non- compliant to medication. Based on the clinical findings and imaging of the brain, he has been diagnosed with “Brain stroke”. His serum total cholesterol is abnormally elevated. Which of the following would also be expected to be abnormally high? A. Chylomicrons B. LDL C. HDL D. VLDL E. IDL The correct option is- B, LDL (Low density lipoprotein) Lipids absorbed from the diet and synthesized by the liver...

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# About the web site

Dear viewers, This web site emphasizes on discussion of the essentials of Biochemistry with Clinical correlations. The purpose of this web site is to present a clear discussion of Biochemistry in relation to physiological processes occurring at the cellular levels and to cite examples of deviant biochemical processes in different clinical conditions. A clinical problem is published and the discussion is held subsequently. Through each case study the fundamentals of the basic defect, entire format of pathophysiology and the clinically relevant details are provided. The motive of this web site is not only to inculcate knowledge but also to make...

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Case study- Starvation

Case details A 25 –year-old woman living alone became severely depressed after the termination of her engagement. Two months later, she was brought to the emergency room by a friend because of weakness and lethargy. She appeared thin and pale. Questioning revealed that she had not eaten for several weeks. Analysis of a plasma sample indicated elevated levels of acetoacetate, β hydroxybutyrate, and blood urea nitrogen (BUN). However her plasma glucose concentration was within normal limits. She was hospitalized, given intravenous feeding and antidepressant medications and subsequently shifted to an 1800 Cal (7500 kJ) diet. Her recovery was uneventful. During...

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Case study- Renal glycosuria

Case details A 22-year-old man collapsed from dehydration during maneuvers in the desert and was sent to the emergency. A high level of glucose was observed in his urine. He was suspected of being a diabetic. Further tests, however, determined that his serum insulin level was normal. A glucose tolerance test exhibited a normal pattern; further testing of the urine revealed that only D-glucose was elevated. Other sugars were not elevated. The patient was diagnosed with, ‘Renal glycosuria’. This patient’s elevated urinary glucose and his dehydration episode are caused by a deficiency in which of the following? A. GLUT 2...

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Methotrexate in rheumatoid arthritis

Case details A 63- year-old woman presents with a long history of joint pains. Physical examination reveals severely deformed fingers secondary to rheumatoid arthritis. The rheumatologist recommends Methotrexate. This drug inhibits which of the following conversions? A. Dopamine to norepinephrine B. Tyrosine to Dopa C. Folate to dihydrofolate D. Histidine to formiminoglutamate (FIGLU) E. Norepinephrine to Vanillylmandelic acid The correct answer is- C. Folate to dihydrofolate conversion. The reaction is catalyzed by dihydrofolate reductase; the same enzyme catalyzes the conversion of Dihydrofolate to tetrahydrofolate. The enzyme is competitively inhibited by Methotrexate, which is also used as an anticancer drug. It...

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Fructose 2, 6 Bis phosphate and regulation of glycolysis

Case details A patient presents with dizziness, fatigue and tremors. A finger stick test indicates blood glucose of 36mmol/L. Of the allosteric activators of glycolysis in the liver, which of the following is the most important in maintaining a normal blood glucose level? A. Citrate B. ATP C. Fructose 2, 6 bisphosphate D. Glucose-6-Phosphate E. Acetyl Co A The correct answer is- C- Fructose 2,6 bisphosphate Generally, enzymes that catalyze essentially irreversible steps in metabolic pathways are potential sites for regulatory control.  Although most of the reactions of glycolysis are reversible, three are markedly exergonic and must therefore be considered...

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Biotin deficiency- A case report

Case details A 23-year-old body builder visits his physician with complaints of fatigue, depression, insomnia, hair loss and dry skin. He tells the physician he has been “bulking up” for an upcoming competition, and his meals consist mostly of eight raw eggs along with low-fat milk. The physician suspects biotin deficiency given the patients’ diet and symptoms. Which of the following is biotin required for? A. The formation of cis-retinal B. Transfer of 1-carbon units C. Hydroxylation reactions D. Carboxylation of pyruvate E. Decarboxylation of α-Keto acids Answer- D- Carboxylation of pyruvate is the right answer. Biotin is required for...

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Biochemical basis of difference in the electrophoretic mobilities of Hb A and HbS

Normal hemoglobin (Hb A) and sickle-cell hemoglobin (Hb S) have different electrophoretic mobilities because these two proteins have different what? A. Amount of bound oxygen B. Amount of bound 2, 3 bisphosphoglycerate C. Charges D. Size E. Hydrophobicity Answer- The correct answer is-C- charges. In Sickle cell disease, also called as sickle-cell anemia, a single nucleotide alteration (point mutation) in the β globin gene of hemoglobin causes a change of thymine for adenine (GAG to GTG.), at the sixth codon of the ß gene. This change encodes Valine instead of Glutamic acid in the sixth position on the ß-globin molecule....

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About the Author- Biochemistry for Medics-Clinical Cases

Dr. Namrata Chhabra is a distinguished Senior-Level Medical Biochemistry Professional with extensive clinical, instructional, research, and administrative experience within prestigious institutions. Over the course of her career she has developed and conducted numerous courses focused on Chemistry, Biochemistry, Research & Analysis, and various other topics. She carries an award-winning track record in conducting high-caliber research, with complementary qualifications in quality management systems and medical laboratory auditing. She has proven herself committed to improving learning experiences for diverse student populations through strategic administrative leadership and curriculum development. She also serves on various academic and extracurricular committees. She also possesses a lengthy...

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‘Hereditary fructose Intolerance’- Case discussion

QUESTION OF THE DAY A 3-month-old girl is brought to the pediatrician due to fussiness and lethargy. According to the parents, the baby was just fine until the mother needed to return to work, and the baby was being switched from breast milk to baby foods, formula, and fruit juices. At that time, the child cried while feeding, sometimes vomited, and had been lethargic. The baby’s appetite seemed to have worsened. The parents thought that if only formula was used, the baby was better, but they really could not remember. Which possible enzyme defect might lead to this case presentation?...

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Case study- Metabolic disorder- A 3-month-old girl is brought to the pediatrician due to fussiness and lethargy….

QUESTION OF THE DAY A 3-month-old girl is brought to the pediatrician due to fussiness and lethargy. According to the parents, the baby was just fine until the mother needed to return to work, and the baby was being switched from breast milk to baby foods, formula, and fruit juices. At that time, the child cried while feeding, sometimes vomited, and had been lethargic. The baby’s appetite seemed to have worsened. The parents thought that if only formula was used, the baby was better, but they really could not remember. Which possible enzyme defect might lead to this case presentation?...

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Case study Malignant hyperthermia (Electron transport chain and oxidative phosphorylation)

Case details A 23-year-old college foot ball player sustains a compound fracture on the field. He is taken to surgery, during which the anesthesiologist notes a significantly increased body temperature (102 0 F). The operation is terminated without completion, as malignant hyperthermia is suspected. Which of the following components of ETC is likely to be responsible for this phenomenon? A. Complex I B. Complex II C. Complex III D. Complex IV E.  ATP synthase complex Answer- The right answer is- E- ATP Synthase complex. Patients with malignant hyperthermia experience uncoupling of oxidative phosphorylation . OXIDATIVE PHOSPHORYLATION Chemiosmosis- As the electrons...

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Introductory message

Welcome to Biochemistry for Medics© – Clinical Cases™.  Our Vision We want this website to be a dynamic environment whereby everyone can interact freely in order to discuss Clinical Cases and solve them. Registration In order to be able to comment on cases, you will need to “register” with us. And the way to do so cannot get any simpler. All you have to do is just click on any one of your preferred Social Accounts amongst Facebook, Twitter, Google, LinkedIn or Microsoft Live, – on the left sidebar – and you shall forever be registered with us. We do...

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