Cytoskeleton MCQs

47 MCQs with clinical pearls · MBBS Biochemistry · Prof Jariya

Topics covered (10)

Hereditary Spherocytosis — 15 MCQs
Cytoskeletal Poisons — 7 MCQs
Cytoskeleton — Intermediate Filaments — 6 MCQs
Cell Cycle — 6 MCQs
DMD / Dystrophin — 5 MCQs
Cytoskeleton Structure and Motors — 4 MCQs
Actin Dynamics — 1 MCQs
Intermediate Filaments — 1 MCQs
Microtubules — 1 MCQs
Cilia and Flagella — 1 MCQs

Sample MCQs with clinical pearls

A 9-year-old boy with progressive proximal muscle weakness has a confirmed dystrophin mutation. His muscle fibres are damaged during contraction because dystrophin normally:

A) Links actin to basal lamina ✔

B) Links actin to myosin

C) Links myosin to sarcolemma

D) Links titin to Z-disc

E) Links tropomyosin to troponin

DYSTROPHIN links intracellular ACTIN to the BASAL LAMINA through the dystrophin-glycoprotein complex, transmitting the force of contraction to the extracellular matrix. Without it the sarcolemma tears during contraction, calcium floods in and the fibre necroses - releasing creatine kinase in the thousands. The gene at Xp21 is the largest in the genome, which is why new mutations are so common. MEMORY: 'Dystrophin is the shock absorber between the fibre and its sheath.'

A muscle physiologist studies dystrophin in normal muscle. Dystrophin ultimately connects the intracellular cytoskeleton to which extracellular matrix protein?

A) Collagen I

B) Collagen IV

C) Fibronectin

D) Laminin ✔

E) Vitronectin

Dystrophin connects through the dystroglycan complex to LAMININ-2 (merosin) in the basal lamina. The whole chain matters clinically: mutations at different points cause different dystrophies - dystrophin gives Duchenne and Becker, sarcoglycans give limb-girdle dystrophies, and laminin-2 gives congenital muscular dystrophy. MEMORY: 'Actin to dystrophin to dystroglycan to laminin - break any link and muscle fails.'

A 10-year-old boy with DMD has pseudohypertrophy of his calf muscles. This occurs because degenerating muscle fibres are replaced by:

A) Bone and cartilage

B) Fat and fibrous tissue ✔

C) Granulation tissue

D) Haematopoietic tissue

E) Smooth muscle

Calf PSEUDOhypertrophy is replacement of muscle by FAT AND FIBROUS TISSUE, not true muscle growth - the calves look large but are weak, which is why the prefix matters. It reflects repeated cycles of necrosis and failed regeneration as the satellite cell pool is exhausted. MEMORY: 'The calves are big because the muscle has been replaced, not because it has grown.'

These are three of 47 MCQs in this section. Every question carries a clinical pearl explaining the reasoning.

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