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Question 1
Incorrect
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Question 2
Correct
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Which of the following substances is involved in the respiratory burst by the neutrophil?
Your Answer: NADPh oxidase
Explanation:The respiratory burst is a rapid release of reactive oxygen species (ROS) from neutrophils and other phagocytes. This process is crucial for the destruction of pathogens. The key components and enzymes involved in the respiratory burst include:
- NADPH oxidase: This enzyme complex plays a central role in the respiratory burst by converting oxygen (O2) into superoxide anion (O2•-), a reactive oxygen species. This is the initial step in the production of various ROS.
- Superoxide dismutase (SOD): This enzyme converts superoxide anion (O2•-) into hydrogen peroxide (H2O2). While SOD is involved in the pathway, the respiratory burst is initiated by NADPH oxidase.
- Myeloperoxidase (MPO): This enzyme uses hydrogen peroxide (H2O2) to produce hypochlorous acid (HOCl) from chloride ions (Cl-), which is a potent antimicrobial agent. Myeloperoxidase also produces other reactive species using halide ions.
- Catalase: This enzyme degrades hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2). While catalase helps to protect the cell from oxidative damage by breaking down H2O2, it is not involved in the generation of ROS during the respiratory burst.
- Adenylate cyclase: This enzyme is involved in the production of cyclic AMP (cAMP) from ATP and is not directly related to the respiratory burst.
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This question is part of the following fields:
- Immunology
- Medicine
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Question 3
Incorrect
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Concerning coronary arteries, what is the net effect of B2 stimulation on the heart (e.g. Running athlete)?
Your Answer: Vasodilation directly
Correct Answer: Vasodilation via production of metabolites
Explanation:The coronary arterioles contain α-adrenergic receptors, which cause vasoconstriction, and β-adrenergic receptors, which cause vasodilation. Activity in the noradrenergic nerves to the heart and injections of norepinephrine cause coronary vasodilation. However, norepinephrine also increases the heart rate and the force of cardiac contraction, and the vasodilation is due to production of vasodilator metabolites in the myocardium secondary to the increase in its activity. As exercise has the same effect as sympathetic stimulation, it will result in vasodilation.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 4
Incorrect
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A 55 year old female presents with progressive dyspnoea, dry cough and fever. She started methotrexate therapy six weeks ago. The current regimen includes methotrexate 15 mg/ week, folic acid 5 mg/day and aspirin 75 mg/day. There is no history of any other chronic illness. Vitals are as follows: Temp: 37.8C, pulse: 100 beats/min, BP: 110/80mmHg and SaO2: 90% on air. Examination reveals synovitis in both wrists, and metacarpophalangeal joints. On auscultation, there are scattered crepitations. Blood test reports are given below:Haemoglobin: 13.1g/dl (13.0 – 18.0 g/dL)WBC: 8.2 x109/l (4 – 11 x 109/l)Neutrophils: 5.1×109/l (1.5 – 7 x 109/l)Platelets: 280 x109/l (150 – 400 x 109/L)ESR: 48 mm/hr (0 – 30 mm/1st hr)Urea, electrolytes and creatinine: normalCXR: patchy airspace shadows bilaterallyWhat is the most likely diagnosis?
Your Answer: Pneumocystis carinii pneumonia
Correct Answer: Methotrexate pneumonitis
Explanation:Pneumonitis is a serious and unpredictable side-effect of treatment with methotrexate (MTX) that may become life-threatening. The typical clinical symptoms include progressive shortness of breath and cough, often associated with fever. Hypoxaemia and tachypnoea are always present and crackles are frequently audible. Chest radiography reveals a diffuse interstitial or mixed interstitial and alveolar infiltrate, with a predilection for the lower lung fields. Pulmonary function tests show a restrictive pattern with diminished diffusion capacity. Lung biopsy reveals cellular interstitial infiltrates, granulomas or a diffuse alveolar damage pattern accompanied by perivascular inflammation. Most patients present in the first few months of starting methotrexate. It is important that all patients receiving methotrexate be educated concerning this potential adverse reaction and instructed to contact their physicians should significant new pulmonary symptoms develop while undergoing therapy. If methotrexate pneumonitis is suspected, methotrexate should be discontinued, supportive measures instituted and careful examination for different causes of respiratory distress conducted. This may be treated with corticosteroids once underlying infection has been excluded.
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This question is part of the following fields:
- Connective Tissue
- Medicine
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Question 5
Correct
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What is the function of the BK channel on the vascular smooth muscle membrane?
Your Answer: Massive K+ efflux, increasing membrane potential, and shutting off the voltage gated Ca2+ channel
Explanation:BK channels, also known as large-conductance calcium-activated potassium channels, play a critical role in regulating vascular smooth muscle tone. When BK channels open, they allow a large efflux of potassium ions (K+) out of the cell. This efflux of K+ causes the membrane potential to become more negative (hyperpolarization), which in turn leads to the closure of voltage-gated calcium channels. The closure of these calcium channels reduces the influx of calcium ions (Ca2+) into the smooth muscle cells, resulting in decreased intracellular calcium levels and subsequent relaxation of the smooth muscle.
Thus, BK channels promote smooth muscle relaxation by hyperpolarizing the membrane and reducing the activity of voltage-gated Ca2+ channels.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 6
Correct
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Consanguinity shows a strong association with which pattern of inheritance?
Your Answer: Autosomal recessive
Explanation:Consanguinity involves being from the same kinship as another person. It is a common feature of an autosomal recessive mode of inheritance
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This question is part of the following fields:
- Genetics
- Medicine
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Question 7
Correct
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Transport of Ca2+ into the reticulum to initiate cardiac muscle relaxation in via:
Your Answer: Serca (sarcoplasmic or endoplasmic reticulum Ca2+ ATPase)
Explanation:Phosphorylation of phospholamban, which increases calcium ATPase activity and sequestration of calcium in the sarcoplasmic reticulum. An increased rate of relaxation is explained because cAMP also activates the protein phospholamban, situated on the membrane of the SR, that controls the rate of uptake of calcium into the SR. The latter effect explains enhanced relaxation (lusitropic effect).
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 8
Correct
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A 45-year-old male is brought to the emergency department after being found collapsed, outside a nightclub. The ER team found an empty bottle of amyl nitrate in his pocket. The patient is hypoxic with an O2 saturation of 84% and is confused. Which of the following is the best treatment for this patient?
Your Answer: Methylene blue
Explanation:The best treatment for the patient in question would be methylene blue.The most probable diagnosis in this patient is methemoglobinemia due to the ingestion of amyl nitrate.Amyl nitrate promotes the formation of methaemoglobin, which avidly conserves oxygen and leads to decreased tissue oxygen saturations. Treatment of choice includes methylene blue and vitamin C.Adverse effects:Benign side effects include green or blue discoloration of urine and patients should be forewarned. Significant side effects are based on methylene blue, itself, being an oxidizing agent and an inhibitor of monoamine oxidase A (MAO-A). As an oxidizing agent, methylene blue can actually precipitate methemoglobinemia or haemolysis in high doses or when ineffectively reduced. Methylene blue administration in a patient taking a serotonergic agents may predispose to serotonin syndrome.Note: Although methylene blue administration is controversial in the setting of G6PD-deficiency due to reduced levels of NADPH, it is not contraindicated and should be administered cautiously and judiciously.
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This question is part of the following fields:
- Medicine
- Pharmacology
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Question 9
Incorrect
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Which of the following values of bone mineral density measured by DEXA would signify osteopenia?
Your Answer: Z score of -1.5
Correct Answer: T score of -2.2
Explanation:DEXA T Scores:Normal T-score ≥ −1.0Osteopenia −2.5 < T-score < −1.0Osteoporosis T-score ≤ −2.5Severe osteoporosis T-score ≤ −2.5 with fragility fracture
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This question is part of the following fields:
- Endocrinology
- Medicine
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Question 10
Correct
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Free radicals are best defined by which of the following statements.
Your Answer: Atoms or molecules with unpaired electrons
Explanation:Free radicals form when one of weak bond between electrons is broken and an uneven number of electrons remain. This means the electron is unpaired, making it chemically reactive and attempt to steal an electron from a neighbouring molecule to stabilize itself.
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This question is part of the following fields:
- Cell Biology
- Medicine
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Question 11
Incorrect
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Regarding Southern Blotting and DNA probes, which answer is FALSE
Your Answer: DNA fragments are separated by gel electrophoresis and transferred onto membrane sheets in southern blotting
Correct Answer: RNA fragments are separated by gel electrophoresis and transferred onto membrane sheets in southern blotting
Explanation:Restriction enzymes always cut at different positions. There are different restriction endonucleases for different nucleotide sequences.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 12
Correct
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With regards to the function of the p53 protein produced by the p53 gene, which of the following statements is incorrect?
Your Answer: It permits repair of mutations and other defects in RNA
Explanation:The p53 protein is a crucial tumor suppressor and plays several key roles in maintaining cellular integrity:
- Nuclear transcription factor: p53 is a nuclear transcription factor that regulates the expression of various genes involved in cell cycle control, DNA repair, apoptosis, and senescence.
- DNA repair: p53 permits repair of mutations and other defects in DNA (not RNA). It activates the transcription of genes involved in DNA repair mechanisms, allowing the cell to correct errors before proceeding with the cell cycle.
- Cell cycle regulation: p53 can induce the expression of p21, a protein that inhibits cyclin-dependent kinases, thereby halting the cell cycle at the G1/S checkpoint to allow time for DNA repair or to trigger apoptosis if the damage is irreparable. Mutations in p53 may fail to halt the cell cycle, allowing mutations to persist and potentially leading to cancer.
- Apoptosis: If DNA damage is extensive and cannot be repaired, p53 triggers apoptosis to prevent the propagation of damaged cells.
- Suppression of proto-oncogenes: p53 indirectly contributes to the suppression of proto-oncogenes by preventing the proliferation of cells with damaged DNA, thereby reducing the risk of oncogenic transformation.
Given these functions, the statement that p53 “permits repair of mutations and other defects in RNA” is incorrect, as p53 is primarily involved in the repair of DNA, not RNA.
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This question is part of the following fields:
- Cell Biology
- Medicine
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Question 13
Correct
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The intestine is lined by:
Your Answer: Simple columnar epithelium
Explanation:In the small intestine, epithelium is simple columnar and specialised for absorption. The epithelium is arranged into villi, creating a brush border and increasing the area for absorption. The epithelium is simple columnar with microvilli.In the colon, epithelium is simple columnar and without villi. Goblet cells, which secrete mucous, are also present.
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This question is part of the following fields:
- Gastrointestinal
- Medicine
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Question 14
Correct
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Cell membrane proteins may act as:
Your Answer: All of the options
Explanation:Membrane proteins perform a variety of functions including:Membrane receptor proteins relay or carry signals between the cell’s internal and external environments.Transport proteins move molecules and ions (ionic channels) across the membrane. Membrane enzymes may have many activities, such as oxidoreductase, transferase or hydrolase andCell adhesion molecules
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This question is part of the following fields:
- Cell Biology
- Medicine
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Question 15
Correct
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An 18 year old girl presents with short history of marked, right hip pain and an associated limp. She has a history of acute lymphoblastic leukaemia for which she completed treatment for last six months.
Your Answer: Avascular necrosis of the femoral head
Explanation:Avascular necrosis (AVN) of the femoral head is a pathological process that results from disruption of the blood supply to the bone and occurs most commonly in the femoral epiphysis. Patients usually present with pain and limited joint motion. The mechanism involves impaired circulation to a specific area that ultimately becomes necrotic. AVN is most frequently associated with high doses of oral and intravenous corticosteroids and prolonged duration of therapy. Cancer patients receiving chemotherapy are usually also treated with corticosteroids.
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This question is part of the following fields:
- Connective Tissue
- Medicine
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Question 16
Correct
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A 50-year-old woman diagnosed with non-Hodgkin's Lymphoma is about to be started on the CHOP regimen (cyclophosphamide, hydroxydaunorubicin, vincristine, and prednisolone). Her pre-chemotherapy blood investigations show:Hb: 11.8 g/dlPlatelets: 423 x 109/lWBC: 11.2 x 109/lNa+: 143 mmol/lK+: 3.9 mmol/lUrea: 6.2 mmol/lCreatinine: 78 μmol/lUric acid: 0.45 mmol/lCiprofloxacin is prescribed in addition to the CHOP regimen to reduce the risk of neutropenic sepsis. Which of the following drugs should be added to lower the risk of other complications?
Your Answer: Allopurinol
Explanation:Tumour lysis syndrome (TLS) occurs most notably in patients with haematological malignancies including, Non-Hodgkin’s Lymphoma (NHL) and Acute Lymphocytic Leukaemia (ALL).Risk factors for TLS include:• Large tumour burden• Sensitivity of the tumour to chemotherapy• Rapid tumour growth rateTLS is characterized by:• Hyperuricemia• Hyperkalaemia• Hyperphosphatemia• HypocalcaemiaTreatment of TLS:• Allopurinol: It is a xanthine oxidase inhibitor, it reduces the conversion of nucleic acid by-products to uric acid. Thus, it prevents urate nephropathy and subsequent oliguric renal failure. Note: dose reduction is essential in renal failure or if given along with mercaptopurine or azathioprine.Alternatives to Allopurinol: Febuxostat; Rasburicase are useful in patients with hyperuricemia.• Hydration• Diuresis: Should be considered in well hydrated patients with insufficient urine output. Furosemide to be considered in normo-volemic patients with hyperkalaemia. Urine alkalization can be considered for promoting alkaline diuresis.• Treatment of electrolyte imbalances including hyperkalaemia, hyperphosphatemia, and hypocalcaemia.• Dialysis can be considered in refractory cases.
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This question is part of the following fields:
- Medicine
- Pharmacology
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Question 17
Correct
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Regarding cardiac muscle contractility, the afterload refers to:
Your Answer: The resistance against which blood is expected
Explanation:The afterload for the left ventricle is the aortic pressure. Hence it is this pressure that offers resistance against which the blood is to be expelled from the heart.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 18
Correct
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Which one of these features is typical of dermatomyositis?
Your Answer: Gottron's papules over knuckles of fingers
Explanation:The main symptom of dermatomyositis include skin rash and symmetric proximal muscle weakness (in over 90% of patients) which may be accompanied by pain and tenderness. It occurs more commonly in females. Skin findings include:Gottron’s sign – an erythematous, scaly eruption occurring in symmetric fashion over the MCP and interphalangeal jointsHeliotrope or lilac rash – a violaceous eruption on the upper eyelids and in rare cases on the lower eyelids as well, often with itching and swellingShawl (or V-) sign is a diffuse, flat, erythematous lesion over the back and shoulders or in a V over the posterior neck and back or neck and upper chest, which worsens with UV light. Erythroderma is a flat, erythematous lesion similar to the shawl sign but located in other areas, such as the malar region and the forehead. Periungual telangiectasias and erythema occur.
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This question is part of the following fields:
- Dermatology
- Medicine
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Question 19
Correct
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Choose the correct statement regarding trabecular bone:
Your Answer: All of the options are correct
Explanation:Trabecular, spongy or cancellous bone. It is located inside the cortical bone and makes up around 20% of all bone in the body. It is made of spicules or plates with a high surface to volume ratio, where many cells sit on the surface of the end plates. It receives its nutrients from the extracellular fluid (ECF), exchanging about 10 mmol of calcium every 24 hours.
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This question is part of the following fields:
- Endocrinology
- Medicine
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Question 20
Correct
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Question 21
Incorrect
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With regards to the deiodinases, where would you find D1?
Your Answer: Brain
Correct Answer: Liver
Explanation:The liver produces an important amount of T3 by outer ring deiodination thanks to its elevated concentration of type I deiodinase. It can also be found in the kidney.
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This question is part of the following fields:
- Endocrinology
- Medicine
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Question 22
Correct
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Question 23
Correct
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All of the following are associated with yellow nail syndrome except:
Your Answer: Cardiomegaly
Explanation:Yellow nail syndrome is a very rare medical syndrome that includes pleural effusions, lymphedema (due to under development of the lymphatic vessels) and yellow dystrophic nails. Approximately 40% will also have bronchiectasis. It is also associated with chronic sinusitis and persistent coughing and it usually affects adults.
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This question is part of the following fields:
- Dermatology
- Medicine
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Question 24
Correct
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Mitosis is the process of cell division which culminates in cell chromosomes which are:
Your Answer: Diploid
Explanation:Mitosis is a part of the cell cycle when replicated chromosomes are separated into two new diploid nuclei.
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This question is part of the following fields:
- Cell Biology
- Medicine
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Question 25
Correct
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What are the three main structures in the portal triad (portal space)?
Your Answer: Branch of hepatic artery, branch of portal vein, bile ductules
Explanation:A portal triad (also known as portal field, portal area, or portal tract) is a distinctive arrangement in the liver. It is a component of the hepatic lobule. It consists of the following five structures:
- Proper hepatic artery
- Hepatic portal vein
- Common bile duct
- Lymphatic vessels
- Branch of the vagus nerve
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This question is part of the following fields:
- Hepatobiliary
- Medicine
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Question 26
Correct
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Which of the following is matched correctly with regard to stem cells of the bone marrow?
Your Answer: Hemopoietic stem cells - basophils
Explanation:Hematopoietic stem cells (HSCs) or hemocytoblasts are the stem cells that give rise to all the other blood cells through the process of haematopoiesis. They give rise to both the myeloid and lymphoid lineages of blood cells. (Myeloid cells include monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, dendritic cells, and megakaryocytes or platelets. Lymphoid cells include T cells, B cells, and natural killer cells.)
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This question is part of the following fields:
- Haematology
- Medicine
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Question 27
Correct
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Direct conduction from the atrium to the ventricles is prevented by:
Your Answer: Annulus fibrosus
Explanation:The annulus fibrosus disconnects the syncytium complex. The atria are rapidly activated however the activation peters out when the insulating layer-the annulus fibrosus-is reached.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 28
Correct
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Closure of the tricuspid valve is marked by which of the following features of the jugular venous waveform?
Your Answer: c wave
Explanation:The jugular venous pressure (JVP) classically has three upward deflections and two downward deflections. The upward deflections are the a (atrial contraction), c (ventricular contraction and resulting bulging of tricuspid into the right atrium during isovolumetric systole) and v = venous filling. The downward deflections of the wave are the x (the atrium relaxes and the tricuspid valve moves downward) and the y descent (filling of ventricle after tricuspid opening).
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 29
Correct
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With regard to X linked disorders which of the following are true
Your Answer: X linked recessive disorders usually present in males and only very rarely present in homozygous females
Explanation:All are true for autosomal recessive disorders. Dominance rules for sex-linked gene loci are determined by their behaviour in the female: because the male has only one allele (except in the case of certain types of Y chromosome aneuploidy), that allele is always expressed regardless of whether it is dominant or recessive.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 30
Incorrect
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Which statement is correct regarding mRNA?
Your Answer: mRNA is only single stranded and cannot hybridize with a complementary sequence of single stranded DNA.
Correct Answer: mRNAs are mainly found in the nucleus and cytoplasm of a cell.
Explanation:mRNA is transcribed from DNA and is carried to the cytosol to be translated. Hence it is mainly found in the cytosol and the nucleus of a cell. It is single stranded and contains the base uracil instead of thymine.
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This question is part of the following fields:
- Genetics
- Medicine
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