CAT 2 2014 — Physiology & Biochemistry MCQs OmpathStudy

CAT 2 2014 — Physiology & Biochemistry MCQs This scan contains seven separate MBChB/BPharm/BDS Level I CAT papers (2013–2015) photographed together, grouped here by paper header/date so each exam reads as one coherent set. Split into three parts for readability — every visible question and option is preserved. PAPER 1: MBChB/BPharm/BDS Level 1 — CAT 2, 3rd December 2014 (Cell Biology / Physiology) Q1. Which of the following statements about carrier-mediated transport systems is NOT true? A. Each carrier protein has a specific affinity for binding one or a small number of solutes B. They are members of the solute carrier (SLC) superfamily C. The simplest passive carrier-mediated transport is one that mediates facilitated diffusion D. They hydrolyze ATP or couple to an electron transport chain E. They transfer a broad range of ions and organic solutes across the cell membrane Answer: d Explanation: Carrier-mediated transport includes facilitated diffusion (passive, no ATP) and active transport. Statement (d) wrongly generalizes that all carriers hydrolyze ATP or couple to electron transport — this only applies to active transporters, not facilitated diffusion carriers. --- Q2. The events that take place at the neuromuscular junction (NMJ), where acetylcholine (ACh) is released as a neurotransmitter, is an excellent example of: A. Autocrine signaling B. Hormonal signaling C. Paracrine signaling D. Self-induced signaling E. Endocrine signaling Answer: c Explanation: Paracrine signaling affects target cells in close proximity to the signaling cell — exactly what happens at the NMJ, where ACh diffuses a very short distance across the synaptic cleft. --- Q3. Which of these statements is TRUE regarding the Na⁺–K⁺ pumps? A. They are energized by GTP hydrolysis and hence are GTPases B. They are responsible in cells throughout the body for maintaining a high [K⁺]ᵢ and low [Na⁺]ᵢ, and are ATPases C. In each cycle, the pump couples the extrusion of two K⁺ ions and the uptake of three Na⁺ ions D. In most epithelial cells they are restricted to the basolateral side of the cell E. They are the least important primary active transporter in human body cells Answer: d (with b also broadly true in principle, but the pump extrudes 3 Na⁺ and takes up 2 K⁺ — opposite of option c) Explanation: The Na⁺/K⁺-ATPase is an ATPase (not GTPase), extrudes 3 Na⁺ out and brings 2 K⁺ in per cycle (so option c is reversed/wrong), and in most epithelial cells is localized to the basolateral membrane , making (d) the correct statement. --- Q4. Intracellular signaling effector molecules include the following, EXCEPT: A. Ligands B. Contractile elements C. Transport proteins and channels D. Transcription factors E. Enzymes Answer: a Explanation: Ligands are extracellular signaling molecules that bind receptors; effectors act downstream inside the cell (enzymes, channels, transcription factors, contractile elements). --- Q5. In the parietal cells of the gastric gland, an across the apical membrane into the gland lumen extrudes H⁺, regulated by histamine, acetylcholine, and gastrin: A. H⁺-K⁺ pump B. Ca²⁺ pump C. Na/K/Cl cotransporter D. K/Cl cotransporter E. Na-K pump Answer: a Explanation: The gastric H⁺/K⁺-ATPase pumps H⁺ into the gland lumen in exchange for K⁺; it is stimulated by histamine, acetylcholine, and gastrin. --- Q6. All the following are categories of receptors based on their associated mechanisms of signal transduction, EXCEPT: A. G protein-coupled receptors B. Catalytic receptors (e.g. tyrosine kinase, activated by binding of ligand) C. Nuclear receptors D. Heterotrimeric guanosine triphosphate (GTP) receptors E. Ligand-gated ion channels Answer: d Explanation: "Heterotrimeric GTP receptors" is not a recognized receptor category — heterotrimeric G-proteins are downstream effectors of GPCRs, not a separate receptor class. --- Q7. With regard to control systems, what is NOT correct? A. The controlled variable is usually a measurable entity B. The controlled system is any process or group of processes whose output is the controlled variable C. The presence of sensors is mandatory for any control system D. The controller may be in the central nervous system E. External influences could be harmful or helpful to the system Answer: c Explanation: Not all control (e.g., simple open-loop/feedforward) strictly requires sensors monitoring the controlled variable — sensors are mandatory for closed-loop feedback control specifically, not for control systems in general. --- Q8. Body fluid compartments: A. This refers to the physical distribution of water within the cells B. Are completely physically and chemically distinct from one another C. Intracellular compartment comprises 14 litres D. Extracellular compartment is 1/3 of the total body water E. Total blood volume is 3.5 litres Answer: d Explanation: ECF is roughly ⅓ of total body water (ICF ≈ ⅔). Intracellular volume is ~28 L (not 14 L), and blood volume is ~5 L (not 3.5 L) in an average adult