This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Cytoskeleton – Intermediate Filaments”.
1. Intermediate filaments are branched structures.
a) True
b) False
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Explanation: Intermediate filaments are strong, flexible, unbranched structures, found only in animal cells. These provide mechanical strength to the cells.
2. Intermediate filaments are _________________
a) heterogenous
b) homogenous
c) labile
d) weak
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Explanation: Unlike microfilaments and microtubules, intermediate filaments are chemically heterogenous, encoded by 70 different types of genes.
3. How many types of polypeptides are found in intermediate filaments?
a) 2
b) 5
c) 10
d) 12
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Explanation: Depending upon the cell type, intermediate filaments are composed of different polypeptide subunits. The polypeptide subunits found in intermediate filaments are divided into 5 major subclasses.
4. The type V intermediate filaments are called ___________
a) lamins
b) collagen
c) lignin
d) fibrin
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Explanation: Classes I, II, III and IV of polypeptide subunits of intermediate filaments are involved in the construction of cytoplasmic filaments. Class V, called lamins, are present as a part of inner lining of the nucleus.
5. Plectins are _____________
a) filaments
b) proteins
c) peripheral organelles
d) fibres
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Explanation: Intermediate filaments radiate through the cytoplasm of a cell and are interconnected to other cytoskeletal elements through cross-bridges. In most cells, these cross-bridges are made up of plectins.
6. Unlike other cytoskeletal elements, in the assembly of intermediate filaments there is no requirement of ______________
a) ATP/ GDP
b) Nucleation
c) Reduction
d) Hydrolysis
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Explanation: Unlike microtubules and microfilaments, in the assembly steps of intermediate filaments there is no direct involvement of ATP or GDP.
7. Intermediate filaments lack polarity.
a) True
b) False
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Explanation: Unlike microtubules and microfilaments, intermediate filaments lack polarity and bothe the ends of the filaments are same in nature.
8. Intermediate filaments tend to be less sensitive to __________________
a) chemicals
b) plectins
c) acidification
d) condensation
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Explanation: Intermediate filaments are less sensitive to chemical agents and difficult to solubilize them, although they behave dynamically in vivo.
9. Which is a type of intermediate filament found in epithelial cells?
a) keratin
b) dynein
c) myosin
d) kinesin
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Explanation: Keratin filaments are found primary in epithelial cells including epidermal cells, liver hepatocytes and pancreatic acinar cells.
10. Neurofilaments are the type _____ intermediate filaments.
a) I
b) II
c) III
d) IV
View Answer
Explanation: Neurofilaments consist of type IV polypeptide subunits of intermediate filaments. Neurofilaments are present in mature nerve cells.
11. Absence of the intermediate filament desmin, has a negative impact on _______________
a) hepatocytes
b) nerve cells
c) epithelial cells
d) muscle cells
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Explanation: Absence of intermediate filaments desmins makes the muscle cells extremely fragile. Desmin polypeptide plays a key role in maintaining the alignment of myofibrils of the muscle cells.
12. Vimentin is a ___________
a) intermediate filament
b) inherited disorder
c) neurodegenerative disease
d) microfilament
View Answer
Explanation: Vimentin is a type III intermediate filament, found in macrophages, fibroblasts, white blood cells. Deficiency of gene expressing vimentin leads to minor abnormalities.
13. ‘Epidermolysis bullosa simplex’ is caused by the deficiency of ____________ polypeptide.
a) myosin
b) keratin
c) kinesin
d) niacin
View Answer
Explanation: ‘Epidermolysis bullosa simplex’ is a genetic disorder that associated with extremely fragile skin that blisters easily. The disease is caused by mutations in the gene encoding K14, a type I keratin polypeptide.
14. Aggregation of neurofilaments leads to ____________
a) vision disorders
b) skin disorders
c) lung disorders
d) neurodegenerative disorders
View Answer
Explanation: Neurofilaments are the intermediate filaments that constitute mature neuronal cells. Aggregation of these neurofilaments blocks axonal transport, associated with neurodegenerative disorders like Alzheimer’s and Parkinson’s disease.
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