End-of-Year 2021 — Past Paper OmpathStudy

1. The genetic defect associated with Fabry's disease is most likely carried on A) The X-chromosome B) Chromosomes of group A C) Chromosome number 2 D) Chromosome number 12 E) A chromosome of group G as a trisomy ✅ Answer: A Explanation: Fabry's disease is an X-linked lysosomal storage disorder caused by a deficiency of alpha-galactosidase A. 2. Amount of dietary iodine in the control of thyroid hormone secretion A) Forcing function B) Sensors C) External influences D) The controller E) Controlled variable ✅ Answer: E Explanation: The body regulates the uptake and utilization of iodine to maintain thyroid hormone levels, making the amount of iodine available a variable that is subject to control. 3. Movement of Cl- ion from gastric cells into the gastric cavity A) diffusion B) none of the above C) filtration D) osmosis E) pinocytosis ✅ Answer: B Explanation: Chloride ions are actively transported into the gastric lumen via specific channels and transporters, which is not described by diffusion, filtration, osmosis, or pinocytosis. 4. Myeloid cells in innate and adaptive immunity EXCLUDE the following: A) Dendritic cell B) Neutrophils C) Mast cells D) Natural killer cells E) Macrophages ✅ Answer: D Explanation: Natural killer (NK) cells are lymphocytes, which are part of the lymphoid lineage, whereas the other options are myeloid cells. 5. The following statement is FALSE about the cells arising from the common lymphoid progenitor A) Natural killer cells are modified T lymphocytes B) Innate lymphoid cells lack antigen specific receptors of the adaptive immune system C) Innate lymphoid cells reside in peripheral tissues such as the intestines D) Dendritic cells function as source of mediators of inflammatory responses E) Natural killer cells express innate receptors ✅ Answer: A Explanation: Natural killer cells are a distinct lineage of lymphocytes that develop from common lymphoid progenitors, separate from T lymphocytes. 6. While complete aerobic oxidation of one mole of glucose in the cell yields 38 moles of ATP, complete catabolism of one mole of a 6- carbon atoms fatty acid through the citric acid cycle yields A) Nearly equal amount of energy molecules B) 82 moles C) 36 moles of ATP but consumes 12 ATPs in the process D) About twice as many ATP molecules of ATP E) 44 moles ✅ Answer: D Explanation: Fatty acids are more reduced than carbohydrates, leading to a higher ATP yield per carbon atom, with longer fatty acids typically yielding about twice the ATP of glucose. 7. 25. Immune privileged sites include the following EXCEPT: A) Testis B) Gravid uterus C) Bone marrow D) Brain E) Eye ✅ Answer: C Explanation: Bone marrow is a primary lymphoid organ, actively involved in immune responses, and is not considered an immune privileged site. 8. 124. Dennis Mwango has cholera. Vibrio cholerae secrete An toxin that is transported and processed in the gut cells. All of the following are true EXCEPT A) An overactive protein kinase A phosphorylates the CFTR (cystic fibrosis transmembrane conductance regulator) chloride channel so that it remains permanently open B) Cholera A toxin cleaves ATP and transfers the ribose-5-phosphate groups to other proteins C) Chloride, sodium and water move into the bowel lumen causing diarrhea and subsequent dehydration D) Cholera A toxin increases the concentration of cAMP and activation of protein kinase A E) Cholera A toxin ADP-ribosylates the Gαs subunit of heterotrimeric G proteins, thereby inhibiting their GTPase activity ✅ Answer: B Explanation: Cholera toxin is an ADP-ribosyltransferase that transfers ADP-ribose from NAD+ to the Gαs subunit, it does not cleave ATP or transfer ribose-5-phosphate. 9. 40. The human genome A) Experiences only negative modification (mutation) when changes occur at meiosis B) Has a capacity to transcript about 2 times it's number in messenger RNA's C) Is made up of 30,000 genes D) Is composed of 3 x 10^6 nucleic base pairs E) Comprises of a total of 50 million genes ✅ Answer: C Explanation: The human genome contains approximately 20,000-25,000 protein-coding genes, with 30,000 being a commonly cited, though slightly outdated, estimate. 10. 61. The following are characteristics of skeletal muscle fibres EXCEPT: A) Extensibility B) Contractility C) Excitability D) Automaticity E) Elasticity ✅ Answer: D Explanation: Skeletal muscle requires nervous stimulation to contract and does not exhibit automaticity, which is the ability to generate its own impulses. 11. 64. Increasing the frequency of stimulation so that a muscle contracts without relaxation is called A) Synergy B) Recovery C) Recruitment D) Tetany E) Treppe ✅ Answer: D Explanation: Tetany is a sustained muscle contraction resulting from a high frequency of stimulation, preventing the muscle from relaxing between stimuli. 12. 120. When a ligand binds to their receptor on the membrane and activate the cAMP cascade, all of the following happen EXCEPT A) GDP dissociates from G-protein and GTP associa