Answer:
Microfilaments, Intermediate filaments and microtubules
Explanation:
Three distinct elements make up the cytoskeleton in eukaryotic cells are:
1. Microfilaments or actin filaments which are composed of actin proteins. The functions of those filaments are: muscle contraction (myosin heads move “walk” on actin filaments), the movement of the cell, intracellular transport, maintaince of the cell shape..
2. Intermediate filaments which can be made of vimentins, keratin, lamin, desmin… Their functions are: the maintenance of cell shape, anchoring organelles, structural components of the nuclear lamina, cell-cell and cell-matrix junctions…
3. Microtubules are filaments polymers of alpha and beta tubulin. Their roles are in intracellular transport (associated with motor protein dyneins and kinesins), formation of the axoneme of cilia and flagella, formation of the mitotic spindle.
No. Zooplankton feed on phytoplankton. Phytoplankton cannot photosynthesize in the dark. (The Benthric Zone is the lowest level of the ocean/a body of water, no sunlight can really reach there.)
The answer is (A) virus. In the medical field, it's considered non-living.
The answer is stem cells. Normal stem cells and germ cells can also be said to be immortal
Answer:
For both actin and microtubule polymerization, nucleotide hydrolysis is important for decreasing the binding strength between subunits on filaments.
Explanation:
Cytoskeletal filaments are common to eucaryotic cells and are impotartant to the spatial organization of cells. Intermediate filaments provide mechanical strength and resistance to shear stress. Microtubules determine the positions of membrane-enclosed organelles and direct intracellular transport. Actin filaments determine the shape of the cell's surface and are necessary for whole-cell locomotion. A large number of accessory proteins are present that link the filaments to other cell components, as well as to each other. Accessory proteins are essential for the assembly of the cytoskeletal filaments in particular locations, and it includes the motor proteins that either move organelles along the filaments or move the filaments themselves.
Actin filaments and microtubules are assembled with expenditure of energy i.e the ATP/GTP tightly bound to actin/tubulin is irreversibly hydrolyzed to ADP/GTP during the assembly process, and liberation of Pi in the medium occurs subsequent to the incorporation of subunits in the polymer. Pi release acts as a switch, causing the destabilization of protein-protein interactions in the polymer, therefore regulating the dynamics of these fibres. The progress is made in four areas: the chemistry of the NTPase reaction; the structure of the intermediates in nucleotide hydrolysis and the nature of the conformational switch; the regulation of parameters involved in dynamic instability of microtubules; and the possible involvement of nucleotide hydrolysis in the macroscopic organization of these polymers in highly concentrated solutions, compared with the simple case of a equilibrium polymers.
