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Question 1
Incorrect
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Dynein proteins transmit polypeptides/proteins in which direction?
Your Answer: Both anterograde and retrograde
Correct Answer: From axons terminals to cell body (retrograde)
Explanation:The majority of axonal proteins are synthesised in the cell body and transported along the axons. Microtubules run along the length of the axon and provide tracks for transportation. Kinesin and Dynein are motor proteins that transport proteins and other organelles. Kinesin moves forward or anterograde transport from cell body to axon, whereas Dynein moves retrograde from axon to cell body.
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This question is part of the following fields:
- Medicine
- Neurology
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Question 2
Incorrect
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If O2 makes up 21% of air, then at one atmosphere (760mmHg) it would be expected that the PO2 of inspired air should be 0,21 x 760 = 160mmHg. In the alveoli the actual measure is 149mmHg because…
Your Answer:
Correct Answer: Water is equilibrated with air
Explanation:There are several factors that determine the value of alveolar partial oxygen pressure including: the pressure of outside air, the partial pressure of inspired oxygen and carbon dioxide, the rates of total body oxygen consumption and carbon dioxide production, the rates of alveolar ventilation and perfusion. The alveolar partial pressure is lower than the atmospheric oxygen partial pressure. One reason is, as the air enters the lungs, it is humidified by the upper airway and thus the partial pressure of water vapour reduces the oxygen partial pressure as water is equilibrated with air.
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This question is part of the following fields:
- Medicine
- Respiratory
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Question 3
Incorrect
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Transportation of proteins from the cell body to axonal terminals is known as:
Your Answer:
Correct Answer: Axoplasmic flow
Explanation:Transportation of proteins from the cell body to axonal terminals is known as axoplasmic, axonal flow or Axonal transport.
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This question is part of the following fields:
- Medicine
- Neurology
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Question 4
Incorrect
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Xanthines (for example Caffeine), exhibit their positive inotropic effect by:
Your Answer:
Correct Answer: Inhibiting the breakdown cAMP
Explanation:Xanthines exert their positive inotropic effect by inhibiting the breakdown of the cAMP resulting in stronger and sustained contraction.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 5
Incorrect
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Southern Blotting and DNA probes:
Your Answer:
Correct Answer: DNA fragments are separated by gel electrophoresis and transferred onto membrane sheets in southern blotting
Explanation:A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization. The other forms of blotting involve the use of RNA and proteins.
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This question is part of the following fields:
- Genetics
- Medicine
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Question 6
Incorrect
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The breakdown of superoxide is catalysed by which enzyme?
Your Answer:
Correct Answer: Superoxide dismutase
Explanation:As superoxide is toxic, nearly all organisms living in the presence of oxygen contain isoforms of the superoxide-scavenging enzyme superoxide dismutase, or SOD. SOD is an extremely efficient enzyme; it catalyses the neutralization of superoxide nearly as quickly as the two can diffuse together spontaneously in solution.
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This question is part of the following fields:
- Cell Biology
- Medicine
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Question 7
Incorrect
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A 38-year-old woman has a melanocytic naevi on her left forearm.Which of the following features do not suggest malignant change?
Your Answer:
Correct Answer: Decrease in size
Explanation:Melanocytic nevi are benign neoplasms or hamartomas composed of melanocytes. Melanocytes are derived from the neural crest and migrate during embryogenesis to selected ectodermal sites (primarily the skin and the CNS), but also to the eyes and the ears.They tend to appear during early childhood and during the first 30 years of life. They may change slowly, becoming raised, changing color or gradually fading.. Pregnancy can increase the number of naevi as well as the degree of hyperpigmentation.They may become malignant and this should be suspected if the naevus increases in size, develops an irregular surface or becomes darker, itches or bleeds.
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This question is part of the following fields:
- Dermatology
- Medicine
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Question 8
Incorrect
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In cardiac muscle, which of the following is directly responsible for the release of Ca2+ stored in the sarcoplasmic reticulum (calcium-induced calcium release)?
Your Answer:
Correct Answer: Ryanodine receptor (RyR)
Explanation:Ryanodine receptor (RyR) is a ligand-gated Ca2+ channel with Ca2+ as its natural ligand. In skeletal muscle, Ca2+ entry from ECF by this route is not required for Ca2+ release. Instead, the DHPR that serves as the voltage sensor unlocks release of Ca2+ from the nearby SR via physical interaction with the RyR. The release is amplified through ca-induced ca release. However, in cardiac muscle, it is the influx of extracellular Ca2+ through the voltage-sensitive DHPR in the T system that triggers ca-induced ca release trough the RyR at the SR.
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This question is part of the following fields:
- Cardiovascular
- Medicine
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Question 9
Incorrect
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An elderly man presents with fever of 38°C and a very severe headache. His BP is 85/50 mm Hg. He has neck stiffness and photophobia. What is the most appropriate management?
Your Answer:
Correct Answer: CT head
Explanation:In elderly patients, symptoms suggestive of meningitis could be due to an intracranial mass lesion (such as abscess, tumour or an intracerebral haematoma). Therefore elderly patients are increased risk of cerebral herniation from an LP. A CT head should be done before an LP to exclude a mass lesion.
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This question is part of the following fields:
- Geriatrics
- Medicine
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Question 10
Incorrect
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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:
Correct 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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