Biology Past Paper PDF

 **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