Question

Indicate whether each of the following descriptions is true of microtubules (MT), microfilaments (MF), intermediate filaments (IF), or none of these (N). More than one response may be appropriate for some statements.
(a) Involved in muscle contraction.
(b) Involved in the movement of cilia and flagella.
(c) More important for chromosome movements than for cytokinesis.
(d) More important for cytokinesis than for chromosome movements in animal cells.
(e) Most likely to remain when cells are treated with solutions of nonionic detergents or solutions of high ionic strength.
(f) Structurally similar proteins are found in bacterial cells.
(g) Their subunits can bind and catalyze hydrolysis of phosphonucleotides.
(h) Can be detected by immunofluorescence microscopy.
(i) Play well-documented roles in cell movement.
(j) The fundamental repeating subunit is a dimer.
MT,
MF,
IF,
MT and MF,
MT and IF ,
MT, IF, MF.

Answer 1

Answer:

(a) Microfilaments

(b) Microtubules

(c) Microtubules

(d) Microfilaments

(e) Intermediate filaments

(f) Microfilaments, intermediate filaments, microtubules

(g) Microfilaments, microtubules

(h) Microfilaments, intermediate filaments, microtubules

(i) Microtubules, microfilaments

(j) Microtubules

Explanation:

Microtubules (MTs) are dimers of the protein tubulin (alpha- and beta-tubulin subunits) and they are major components of the cytoskeleton. MTs play diverse cellular roles including, mechanical support (cytoskeleton), transport, motility, chromosome segregation, etc. Microfilaments (MFs) are protein filaments that also form part of the cytoskeleton in eukaryotic cells. MFs consist of G-actin monomers assembled in linear actin polymers, and their functions include mechanical support, cytokinesis, changes in cell shape, amoeboid movement, endocytosis and exocytosis, etc. MFs associate with the protein myosin to generate muscle contractions. Actin filaments/MTs assembly from monomeric actin/tubulin is caused due to energy expenditure, where ATP/GTP bound to actin/tubulin is hydrolyzed during polymerization. Finally, intermediate filaments (IFs) are a type of cytoskeletal element composed of a heterogeneous group of structural elements, and they are not found in all eukaryotes. The primary function of the IFs is to contribute to the mechanical support for the plasma membrane where these filaments come into contact with other cells and/or with the extracellular matrix. The IFs are not directly involved in cell movement. All 3 types of cytoskeletal elements (microfilaments, intermediate filaments, microtubules) can be visualized by fluorescence microscopy when cells express chimeric MT/IF/MF.–GFP fusion proteins.