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#exam questions

463 public questions tagged with this topic.

Equation of Continuity and Flow Rate

A pipe has a cross-sectional area of 0.02m2 at one end and 0.01m2 at the other. If water flows at 2m/s through the wider

Using the equation of continuity: A1v1 = A2v2. A1 = 0.02m2, v1 = 2m/s, A2 = 0.01m2. v2 = A1v1A2 = 0.02×20.01 = 4m/s. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 4 m/s. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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Universal Law of Gravitation

A 75kg person stands on two bones, each with area 24cm2. What is the average pressure on the bones? (Take g\=9.8m/s2)

Pav = FA, F = mg = 75×9.8 = 735N. Total area A = 2×24×10−4 = 4.8×10−3m2. Pav = 7354.8×10−3 = 1.53125×105Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.53 × 10⁵ Pa. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.

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Fluid Pressure, Pascal's Law and Manometers

A hydraulic system has a small piston (0.005m2) and a large piston (0.025m2). If 80N is applied on the small piston, wha

Pascal’s law: P = F1A1 = F2A2. F2 = F1×A2A1. F1 = 80N, A1 = 0.005m2, A2 = 0.025m2. F2 = 80×0.0250.005 = 80×5 = 400N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 400 N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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Fluid Pressure, Pascal's Law and Manometers

What assumption does Bernoulli’s principle make about fluid flow that limits its application to real fluids?

Bernoulli’s principle assumes zero viscosity (non-viscous flow), ignoring frictional losses that occur in real fluids, where viscosity converts kinetic energy into heat, reducing its applicability. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Zero viscosity. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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Paracrine Factor

Which of the following Wnt signaling pathways is β-catenin dependent?

Canonical Wnt pathway depends strictly on beta-catenin as transcriptional coactivator linking membrane to nucleus. Wnt binding to Frizzled cysteine-rich domain and LRP5/6 co-receptor recruits Dishevelled scaffold polymerizing via DIX domain, disassembling destruction complex composed of Axin, APC, GSK3, CK1alpha. Stabilized beta-catenin accumulates cytosol, enters nucleus via importin, binds TCF/LEF replacing Groucho corepressor recruiting Legless to activate targets like c-Myc, Cyclin D1, Axin2. Non-canonical pathways include Planar Cell Polarity via Rho-JNK orienting hairs and convergent extension, and Calcium via PKC-CamKII antagonizing canonical. Discrimination underlies diverse Wnt functions.

Ref: Logan & Nusse, Annual Review Cell Dev Biol 2004: Canonical Wnt pathway stabilizes beta-catenin via Frizzled and LRP.

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Paracrine Factor

Which of the following is the primary transcription factor activated in the Hedgehog signaling pathway?

Gli family members Gli1, Gli2, Gli3 are zinc finger transcription factors homologous to Drosophila Cubitus interruptus mediating Hedgehog transcriptional response. In resting state, Suppressor of Fused Sufu sequesters Gli in cytoplasm, promoting sequential phosphorylation by PKA, GSK3, CK1 creating beta-TrCP degron generating repressor Gli3R that blocks targets like Patched1. Upon Hedgehog activation, Smoothened inhibits Sufu and PKA processing, allowing full-length Gli activators Gli1, Gli2A to enter nucleus, inducing Patched1, Gli1 itself, cyclins, Myc, Bcl2. TCF is Wnt effector, STAT cytokine effector, beta-catenin coactivator not Hedgehog specific, making Gli definitive readout.

Ref: Briscoe & Thérond, Nature Reviews Mol Cell Biol 2013: Gli/Ci transcription factors mediate Hedgehog target gene activation.

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Protein Sorting and Trafficking

Which signal is necessary for targeting soluble lysosomal enzymes?

Among diverse sorting determinants mannose-6-phosphate uniquely marks entire class of soluble lysosomal precursors enabling intracellular lysosome biogenesis. Newly synthesized acid hydrolases enter ER lumen, receive high-mannose N-glycans via oligosaccharyltransferase, fold with calnexin, move to cis-Golgi where Golgi-resident phosphotransferase adds M6P as phosphodiester then uncovered in TGN to yield exposed phosphate. Carbohydrate address recognized in TGN pH 6.7 by two M6P receptors both P-type lectins: 300 kDa cation-independent IGF2 receptor binding also IGF2 and 46 kDa cation-dependent requiring divalent cation. Receptors cluster via cytosolic motifs YXXPhi and DXXLL binding AP1 and GGA recruiting clathrin lattice. KDEL retrieval maintains ER chaperones BiP via KDEL receptor and COPI, DXE mediates ER exit for membrane cargo via Sec24 COPII, NPXY plus AP2 handles plasma membrane endocytosis via ARH co-adaptor. Without M6P addition or receptor, lysosomal enzymes follow default secretion to extracellular medium. Experimental addition exogenous M6P competes for receptor binding abolishing sorting confirming receptor-ligand nature essential for lysosome formation and cell physiology.

Ref: Lodish et al., MCB: Mannose-6-phosphate signal targets soluble lysosomal enzymes to lysosomes.

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