Cell Biology Questions and Answers – Non-muscle Motility – 1

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This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Non-muscle Motility – 1”.

1. 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.
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2. 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. 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. 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. 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. 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.
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7. 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. 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. 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. 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. 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. 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: The contractile machinery of nonmuscle cells lie just beneath the plasma membrane. Most of the activities in which the membrane protrudes outwards (during locomotion) or invaginates inwards (during cytokinesis, phagocytosis) are facilitated by indirectly linking the plasma membrane to actin filaments. This linkage is mediated by peripheral membrane-binding proteins, dystrophin is an example belonging to the spectrin family of proteins.
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13. 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. 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. Lamellipodium is a protrusion of ________________
a) actin filaments
b) fibroblasts
c) myoblasts
d) neurons
View Answer

Answer: b
Explanation: When a piece of living tissue is cultured in a dish in apt medium, individual fibroblast cells move out of the specimen and into the dish. The leading edge of these fibroblasts is called lamellipodium.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn