MCB 150 Final Exam Questions and Answers Latest 2022
Which of the following is not a cellular activity associated with microtubules?
a. maintenance of axons
b. maintenance of cell shape
c. cytokinesis of animal cell
d. axonemal structure
e. formation of mitotic spindle Ans- c
Microtubules have an inner diameter of ________ and an outer diameter of ________.
a. 15 mm; 25 mm
b. 8 nm; 12 nm
c. 25 nm; 30 nm
d. 15 nm; 25 nm
e. 7 mm; 14 mm Ans- d
Which stage of microtubule assembly is the stage in which nucleation occurs?
a. sheets of protofilaments
b. closing of microtubules
c. oligomers
d. dimers
e. elongation Ans- c
Which one of the following statements about microtubules is correct?
Microtubules:
a. require ATP hydrolysis for growth.
b. are static structures within a cell.
c. are made up of tubulin heterotetramers.
d. are made up of 13 linear protofilaments.
e. are symmetrical rather than polar structures. Ans- d
Critical concentration is...
a. the concentration of tubulin dimers at which assembly is balanced with disassembly.
b. the concentration of tubulin dimers at which assembly occurs primarily.
c. the concentration of G-actin in most muscle cells.
d. required before nucleation can occur.
e. both choices A and D Ans- a Which one of the following statements about dynamic instability of microtubules is correct? Dynamic instability:
a. was first shown by Watson and Crick in 1952.
b. describes the alternating cycles of growth and shrinkage in microtubules.
c. describes the frequent cleavage of microtubules near the middle of its length.
d. describes the growth of microtubules when the concentration of GTP-bound tubulin is
low.
e. describes the behavior of the stock market in economics. Ans- b
The minus (-) ends of microtubules are often anchored at the ________________ , such that the dynamics associated with microtubules is at the plus (+) ends. a. centriole
b. centrosome
c. plasma membrane
d. centromere
e. mitochondrial outer membrane Ans- b
Which motor protein(s) can move cargo-containing vesicles along microtubule tracks?
a. Kinesin only
b. Myosin and dynein
c. Kinesin and myosin
d. Kinesin and dynein Ans- d
The cilia and flagella of eukaryotic cells are composed of _____.
a. microfilaments
b. pili
c. tonofilaments
d. intermediate filaments
e. microtubules Ans- e
Centrioles, cilia, flagella, and basal bodies have remarkably similar structural elements and arrangements. Which of the following hypotheses is most plausible in light of such structural similarities?
a. Natural selection for cell motility repeatedly selected for microtubular arrays in circular
patterns in the evolution of each of these structures.
b. Motor proteins such as dynein must have evolved before any of these four kinds of structure.
c. Cilia and flagella arise from centrioles.
d. Loss of basal bodies should prevent cells from dividing in two.
e. Cilia and flagella evolved separately in the same ancestral eukaryotic organism. Ans- c
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