Biology Past Paper PDF
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This document includes a set of multiple-choice biology questions focused on cytoskeletal structures and processes. The questions cover topics such as protein filaments, cellular structures, and muscle contraction. These kinds of questions are common in secondary school exams on cell biology.
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**Which of the following is NOT one of the three types of protein filaments that make up the cytoskeleton?** - A\) Intermediate filaments - B\) Microtubules - C\) Actin filaments - D\) Collagen fibers **What are intermediate filaments primarily composed of?** - A\) Tubulin dimers...
**Which of the following is NOT one of the three types of protein filaments that make up the cytoskeleton?** - A\) Intermediate filaments - B\) Microtubules - C\) Actin filaments - D\) Collagen fibers **What are intermediate filaments primarily composed of?** - A\) Tubulin dimers - B\) Actin monomers - C\) Fibrous proteins with an α-helical rod domain - D\) Myosin filaments **Which structure disassembles and reforms during each cell division?** - A\) Microtubules - B\) Nuclear lamina - C\) Centrosome - D\) Actin cortex **Which phosphorylation process controls the disassembly of the nuclear lamina?** - A\) GTP hydrolysis - B\) ATP hydrolysis - C\) Phosphorylation of lamins - D\) Phosphorylation of tubulin **What is the structural composition of microtubules?** - A\) Single α-tubulin filaments - B\) 13 parallel protofilaments made of tubulin dimers - C\) Coiled-coil dimers - D\) Keratin filaments **Where is the minus end of microtubules embedded in animal cells?** - A\) Plasma membrane - B\) Actin cortex - C\) Centrosome - D\) Nuclear lamina **What is the major microtubule-organizing center in animal cells?** - A\) Nucleus - B\) Centrosome - C\) Cytoplasm - D\) Nuclear envelope **What drives the dynamic instability of microtubules?** - A\) GTP hydrolysis - B\) ATP hydrolysis - C\) Dynein movement - D\) Myosin interaction **What prevents a microtubule from disassembling when stabilized?** - A\) Binding of GDP-bound tubulin - B\) Attachment to a cell structure or molecule - C\) Binding of ATP-bound tubulin - D\) Phosphorylation of intermediate filaments **Which motor protein moves toward the plus end of microtubules?** - A\) Kinesin - B\) Dynein - C\) Myosin - D\) Actin **Which motor protein moves toward the minus end of microtubules?** - A\) Kinesin - B\) Dynein - C\) Myosin-I - D\) Myosin-II **What structure contains a "9 + 2" arrangement of microtubules?** - A\) Centrosome - B\) Cilia and flagella - C\) Sarcomere - D\) Actin cortex **What generates the sliding force that causes bending in cilia and flagella?** - A\) Myosin filaments - B\) Kinesins - C\) Dyneins - D\) Actin filaments **What is the function of myosin-I in cells?** - A\) It transports vesicles - B\) It moves toward the minus end of actin filaments - C\) It forms thick muscle filaments - D\) It binds intermediate filaments **Which actin-binding protein promotes actin polymerization at the leading edge of crawling cells?** - A\) Tropomyosin - B\) Myosin-I - C\) Kinesin - D\) Actin-binding proteins **What mechanism allows actin filaments to undergo "treadmilling"?** - A\) GTP hydrolysis at both ends - B\) ATP hydrolysis at the plus end - C\) ATP hydrolysis at the minus end while adding monomers at the plus end - D\) Phosphorylation of actin **Where are the plus ends of actin filaments attached in muscle cells?** - A\) Sarcomere - B\) Z-disc - C\) Centrosome - D\) Myosin filaments **What triggers muscle contraction?** - A\) Binding of ATP to myosin - B\) GTP hydrolysis - C\) Release of Ca2+ from the sarcoplasmic reticulum - D\) Phosphorylation of actin **What type of myosin is involved in muscle contraction?** - A\) Myosin-I - B\) Myosin-II - C\) Myosin-III - D\) Myosin-V **What is the primary function of intermediate filaments?** - A\) Resist mechanical stress - B\) Facilitate cell movement - C\) Organize cell division - D\) Transport organelles **Which of the following structures is associated with intermediate filaments?** - A\) Sarcoplasmic reticulum - B\) Nuclear lamina - C\) T-tubules - D\) Centrosomes **What causes microtubules to shrink during dynamic instability?** - A\) GTP hydrolysis faster than dimer addition - B\) ATP hydrolysis - C\) Loss of actin filaments - D\) Binding of tropomyosin **Which protein is involved in actin-based muscle contraction?** - A\) Tubulin - B\) Kinesin - C\) Myosin-II - D\) Dynein **What is the role of Ca2+ in muscle contraction?** - A\) It binds to myosin heads - B\) It triggers the release of ATP - C\) It binds to troponin to allow myosin-actin interaction - D\) It depolymerizes actin filaments **Which structure is responsible for organizing the internal layout of a cell?** - A\) Microtubules - B\) Actin filaments - C\) Myosin-II - D\) Intermediate filaments **Which class of intermediate filaments is found in nerve cells?** - A\) Keratin filaments - B\) Vimentin - C\) Neurofilaments - D\) Nuclear lamins **What helps stabilize actin filaments in the intestinal microvilli?** - A\) Motor proteins - B\) Myosin-I - C\) Spectrin - D\) Tropomyosin **Which molecule binds and hydrolyzes ATP during muscle contraction?** - A\) Actin - B\) Tubulin - C\) Myosin - D\) Dynein **What forms the core of cilia and flagella?** - A\) Actin filaments - B\) Myosin filaments - C\) Microtubules - D\) Intermediate filaments **What component of the cytoskeleton allows the cell to crawl?** - A\) Microtubules - B\) Intermediate filaments - C\) Actin cortex - D\) Nuclear lamins **Where are actin filaments most densely concentrated in a cell?** - A\) Nucleus - B\) Cytoplasm - C\) Plasma membrane - D\) Centrosome **Which motor protein is involved in vesicle transport along actin filaments?** - A\) Dynein - B\) Kinesin - C\) Myosin-I - D\) Tubulin **How is the dynamic instability of microtubules regulated?** - A\) Phosphorylation of microtubules - B\) GTP binding and hydrolysis by tubulin - C\) ATP binding to actin - D\) Myosin motor activity **What structure is responsible for muscle fiber contraction?** - A\) Actin cortex - B\) Myofibrils - C\) Cilia - D\) Centrosome **What happens when GTP is hydrolyzed to GDP in microtubules?** - A\) The microtubule stabilizes - B\) The microtubule disassembles - C\) Myosin binds to tubulin - D\) Vesicle transport begins 36. **Which of the following processes involves actin polymerization?** - A\) Muscle contraction - B\) Formation of microvilli - C\) Treadmilling - D\) ATP hydrolysis 37. **What process is responsible for shortening the sarcomere during muscle contraction?** - A\) Disassembly of actin filaments - B\) Sliding of actin filaments past myosin filaments - C\) GTP hydrolysis - D\) Vesicle transport along actin filaments 38. **Which of the following is involved in the formation of the contractile ring during cell division?** - A\) Microtubules - B\) Intermediate filaments - C\) Actin filaments and myosin - D\) Centrosomes 39. **What triggers the release of Ca2+ from the sarcoplasmic reticulum in muscle cells?** - A\) ATP binding to myosin - B\) Action potential from motor neurons - C\) GTP hydrolysis - D\) Myosin binding to actin 40. **In which part of the cell does actin associate with myosin-I to change the shape of the plasma membrane?** - A\) Cytoplasm - B\) Actin cortex - C\) Centrosome - D\) Nucleus 41. **What happens to the muscle when Ca2+ is rapidly pumped back into the sarcoplasmic reticulum?** - A\) The muscle contracts - B\) The muscle relaxes - C\) Myosin binds more tightly to actin - D\) Actin filaments depolymerize 42. **Which structure organizes microtubules during mitosis in animal cells?** - A\) Sarcomere - B\) Centrosome - C\) Actin cortex - D\) Sarcoplasmic reticulum 43. **What allows microtubules to grow from the centrosome?** - A\) GTP cap - B\) ATP hydrolysis - C\) γ-tubulin ring complex - D\) Actin-binding proteins 44. **What type of actin-based structure is found in crawling cells?** - A\) Microtubules - B\) Z-discs - C\) Lamellipodia - D\) Sarcomeres 45. **Which structure is stabilized by proteins to prevent the disassembly of actin filaments?** - A\) Sarcomere - B\) Plasma membrane - C\) Actin cortex - D\) Centrosome 46. **What structure contains actin filaments and spectrin in red blood cells?** - A\) Nucleus - B\) Cytoskeleton - C\) Cortical actin - D\) Plasma membrane 47. **What is the role of tropomyosin in muscle cells?** - A\) It blocks myosin-binding sites on actin filaments - B\) It hydrolyzes ATP for muscle contraction - C\) It transports vesicles along actin filaments - D\) It stabilizes microtubules during cell division 48. **Which component of muscle cells stores and releases calcium during contraction?** - A\) Sarcomere - B\) T-tubules - C\) Sarcoplasmic reticulum - D\) Z-disc 49. **What structure is responsible for the rhythmic beating of cilia and flagella?** - A\) Intermediate filaments - B\) Dynein motor proteins - C\) Myosin-II - D\) Z-discs 50. **Which protein acts as a molecular switch to initiate muscle contraction upon binding Ca2+?** - A\) Tropomyosin - B\) Troponin - C\) Myosin - D\) Tubulin