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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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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