Engineering Questions with Answers - Multiple Choice Questions

MCQs on Non-muscle Motility – 1

1 - Question

Cortex (of a cell) is located beneath the _____________ a) nucleus b) mitochondria c) ribosomes d) plasma membrane
View Answer Answer: d Explanation: Cortex of a cell is located just beneath the plasma membrane. It is an active region of the cell that participates in ingestion of extracellular materials, cell division and motility.



2 - Question

Which type of cytoskeletal elements are involved in nonmuscle motility? a) microfilaments b) flagella c) intermediate filaments d) microtubules
View Answer Answer: a Explanation: Microfilaments primarily constitute the cortex of a cell and aid in the process of cell motility. All the associated process depends on the assembly of microfilaments in the cortex.



3 - Question

Nucleation is the slowest step in actin filament formation. a) True b) False
View Answer Answer: a Explanation: The slowest step in the formation of actin filaments is nucleation. At least two or three actin monomers come together in proper orientation in this step.



4 - Question

Which of the following nucleating protein generates unbranched actin filaments? a) formin b) kinesin c) globulin d) vimentin
View Answer Answer: a Explanation: Formin is a nucleating protein that helps in the nucleation of actin filaments. It helps in the generation of unbranched filaments such as those found in focal adhesions.



5 - Question

. Which of the following binds to G-actin? a) thymosin b) lysin c) kinesin d) chymosin
View Answer Answer: a Explanation: Thymosins are the proteins that bind to G-actin and prevent their polymerization. Actin-ATP monomers are referred to as G-actin.



6 - Question

Monomer-sequestering proteins are responsible for high concentration of G-actin in nonmuscle cells. a) True b) False
View Answer Answer: a Explanation: Monomer-sequestering proteins such as thymosin β4 are responsible for high concentration of G-actin in nonmuscle cells.



7 - Question

Tropomodulin is a ___________ a) monomer-sequestering protein b) capping protein c) monomer unit d) motor protein
View Answer Answer: b Explanation: Tropomodulin is a capping protein that caps the pointed ends of the actin filaments. The capping proteins regulate the length of actin filaments.



8 - Question

. Which of the following has an opposing role as that of thymosin? a) chymosin b) vimentin c) profilin d) niacin
View Answer Answer: c Explanation: Profilin has the role of binding to G-actin and promoting the growth of actin filaments rather than inhibiting (like thymosin).



9 - Question

Which of the following can fragment actin filaments? a) profilin b) thymosin c) cofilin d) vimentin
View Answer Answer: c Explanation: Cofilin is a family of proteins that include ADF, depactin. These proteins can fragment actin filaments and can promote depolymerization at the pointed end.



10 - Question

. Filamin is an example of ___________ proteins. a) capping b) depolymerization c) motor d) cross-linking
View Answer Answer: d Explanation: Filamin is a cross-linking protein; such proteins have the ability to alter three-dimensional organization of a population of actin filaments.



11 - Question

Cross-linking proteins villin and fimbrin are found in ___________ a) neurons b) myoblasts c) microvilli d) flagella
View Answer Answer: c Explanation: Villin and fimbrin are globular cross-linking proteins that promote the bundling of actin filaments into parallel and tightly-knit arrays. Such arrays are found in microvilli of epithelial cells.



12 - Question

The protein responsible for muscular dystrophy, dystrophin, is a __________ protein. a) cross-linking b) membrane-binding c) tethering d) severing
View Answer Answer: b Explanation: Dystrophin is a cylindrical shaped protein made up of about 3700 amino acid residues and is present in the muscles. It attaches the muscle fibres to the surrounding extracellular matrix thereby acting as a membrane binding protein.



13 - Question

An organism in which cell motility takes place solely as a result of actin polymerization is ____________________ a) E. coli b) Corynebacterium c) Listeria monocytogenes d) Clostridium botulinum
View Answer Answer: c Explanation: In the bacterium Listeria monocytogenes which infects the macrophages and causes food poisoning, cell motility is facilitated solely by the polymerization of actin.



14 - Question

ActA, a surface protein activates the ______________ a) Arp2/3 complex b) Sar1 c) Arf1 d) EcoR1
View Answer Answer: a Explanation: ActA is a surface protein found on one side of the bacterium Listeria monocytogenes, when inside the host cell it activates the Arp 2/3 complex and other proteins that work together to direct the process of actin polymerization.



15 - Question

Lamellipodium is a protrusion of ________________ a) actin filaments b) fibroblasts c) myoblasts d) neurons
View Answer Answer: a Explanation: Lamellipodium is a cellular extension that occurs in motile cells such as fibroblasts and keratinocytes. These projections are caused by actin filaments and are seen on the edges of the cells.

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