CAT 2 2014 — Physiology & Biochemistry MCQs OmpathStudy

CAT 2 2014 — Physiology & Biochemistry MCQs (Part 3 of 3) Continued from $1. Covers Papers 6–7, the final papers in this combined set. PAPER 6: MBChB/BPharm/BDS — CAT II, 14th August 2013 (Cell Membrane, Signaling, Control Systems) Q1. Concentration of cations expressed in milliequivalents per litre of solution: A. Is the same as molar concentration expressed in milliequivalents B. Is equivalent to molar concentration for fully dissociating compounds C. Is the same as molar concentration multiplied by the valence of the specific ion D. Is not influenced by Donnan-Gibbs equation E. Can be used to compare concentrations of albumin and urea in plasma Answer: c Explanation: Equivalents = moles × valence; milliequivalents/L therefore equals molar concentration × valence of the ion for fully dissociating compounds. --- Q2. The one solution among the following whose osmotic concentration does NOT approximate 300 mmol/L is: A. Ringer's lactate solution B. 0.9 g of NaCl per deciliter of water C. Body's intravascular fluid D. 10% dextrose solution E. 5% dextrose in Normal saline Answer: e Explanation: 5% dextrose in normal saline is hypertonic (~560 mOsm/L combined), far above the ~300 mOsm/L of plasma/Ringer's lactate/isotonic solutions; note 10% dextrose is also hypertonic, but the marked answer here is (e). --- Q3. The correct sequence of events during depolarization at the cell membrane is: A. Slow Na⁺ flow inwards → passive leak outwards → sudden Ca²⁺ entry → depolarization; movement of other ions B. Slow K⁺ leak outwards → passive Na⁺ flow inwards → sudden Na⁺ influx followed by depolarization C. Pumping of Na⁺ into the cell → opening of K⁺ channels → influx of other ions → depolarization D. Opening of K⁺ channels → sudden influx of K⁺ → slow Ca²⁺ inflow → depolarization E. Arrival of Action Potential → activation of ATPase pump → pumping of Na⁺ into the cell and K⁺ out of the cell → depolarization Answer: b Explanation: At rest there is slow passive K⁺ leak/Na⁺ inflow; upon reaching threshold, a sudden, rapid influx of Na⁺ (through voltage-gated channels) produces depolarization. --- Q4. Cellular components that use their contractile tubulin elements to transport molecules within the cell include: A. Cytoskeleton and endoplasmic reticulum formation B. Endoplasmic reticulum and microtubules C. Molecular motors and centrioles D. The cytoskeleton and the centrioles E. Actin and myosin Answer: d Explanation: Microtubules (tubulin-based) form part of the cytoskeleton, and centrioles are also tubulin-based structures involved in organizing microtubule-dependent transport. --- Q5. BMI for a physiological normal man approximates: A. Weight for height for age B. Height per weight per girth C. Weight for surface area D. A value of 32 E. That of a 40-year-old, 80 kg, 1.3 m tall man Answer: c (Note: BMI = weight/height², a "weight-for-surface-area-like" index; a normal BMI is ~18.5–24.9, so option (d) "a value of 32" would be obese, not normal.) --- Q6. These are specialized intercellular connections EXCEPT: A. Desmosomes B. Basement membrane C. Gap junctions D. Tight junctions E. Zonula occludens Answer: b (repeat of Paper 2 Q6) --- Q7. The following statements apply to lysosomes EXCEPT: A. Packaged by Golgi apparatus B. Appear in granulocytes C. Inhibit intracellular digestion D. Alteration of pH E. Digest products of receptor-mediated endocytosis Answer: c Explanation: Lysosomes facilitate (not inhibit) intracellular digestion, breaking down material via acid hydrolases. --- Q8. The following processes occur during protein synthesis EXCEPT: A. Transcription B. DNA translocation C. Translation D. RNA translocation E. t-RNA activation Answer: b Explanation: "DNA translocation" is not a step of protein synthesis; DNA remains in the nucleus while mRNA is transcribed, processed, and exported (RNA translocation) for translation. --- Q9. Which statement may NOT hold true regarding second messengers? A. Intracellular mediators B. Mediate effects of hormones C. Destruction can be localized D. Are enzymes E. Can cross gap junctions Answer: d Explanation: Second messengers (cAMP, IP₃, Ca²⁺, DAG) are small molecules/ions, not enzymes themselves (though they activate enzymes). --- Q10. The following statements apply to protein kinase G EXCEPT: A. Phosphorylates proteins B. Requires ATP C. Exists as a dimer D. cGMP binds to regulatory sites E. Activation causes subunits to dissociate Answer: e Explanation: Unlike protein kinase A (which dissociates into catalytic and regulatory subunits upon activation), PKG remains a dimer with cGMP-binding domains on the same polypeptide — it does not dissociate. --- Q11. Inositol 1,4,5-triphosphate (IP₃) mediates the following actions EXCEPT: A. Diffuses through cytosol B. Binds smooth endoplasmic reticulum C. Binds mitochondria D. Increases cytosolic calcium E. Binds calmodulin Answer: c Explanation: IP₃ acts on IP₃ receptors on the smooth ER to release Ca²⁺; it does not act directly on mitochon