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The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. [2] In eukaryotes , it extends from the cell nucleus to the cell membrane and is composed of similar proteins in the various organisms.
Micrograph showing condensed chromosomes in blue, kinetochores in pink, and microtubules in green during metaphase of mitosis. In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells.
Microtubule and tubulin metrics [1]. Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm [2] and have an inner diameter between 11 and 15 nm. [3]
The prokaryotic cytoskeleton is the collective name for all structural filaments in prokaryotes. [2] Some of these proteins are analogues of those in eukaryotes , while others are unique to prokaryotes.
Cell walls may or may not be present. The eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins. All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. [2] Some eukaryotic organelles such as mitochondria also contain some DNA.
Compared to the other parts of the cytoskeletons, the microfilaments contain the thinnest filaments, with a diameter of approximately 7 nm. Microfilaments are part of the cytoskeleton that are composed of protein called actin. Two strands of actin intertwined together form a filamentous structure allowing for the movement of motor proteins.
The mitotic spindle can be seen, stained green, attached to the two sets of chromosomes, stained light blue. All chromosomes but one are already at the metaphase plate. During its lifetime, a nucleus may be broken down or destroyed, either in the process of cell division or as a consequence of apoptosis (the process of programmed cell death ...
DNA exists in many possible conformations that include A-DNA, B-DNA, and Z-DNA forms, although only B-DNA and Z-DNA have been directly observed in functional organisms. [14] The conformation that DNA adopts depends on the hydration level, DNA sequence, the amount and direction of supercoiling, chemical modifications of the bases, the type and ...