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The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
Many components of animal cells are recycled by transferring them inside or embedded in sections of membrane. For instance, in endocytosis (more specifically, macropinocytosis), a portion of the cell's plasma membrane pinches off to form vesicles that will eventually fuse with an organelle within the cell. Without active replenishment, the ...
In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells.
Lynn Margulis advanced and substantiated the theory with microbiological evidence in a 1967 paper, On the origin of mitosing cells. [19] In her 1981 work Symbiosis in Cell Evolution she argued that eukaryotic cells originated as communities of interacting entities, including endosymbiotic spirochaetes that developed into eukaryotic flagella and ...
A cell's ability to vitrify in the absence of metabolic activity, as in dormant periods, may be beneficial as a defense strategy. A solid glass cytoplasm would freeze subcellular structures in place, preventing damage, while allowing the transmission of tiny proteins and metabolites, helping to kickstart growth upon the cell's revival from ...
The cell nucleus (from Latin nucleus or nuculeus 'kernel, seed'; pl.: nuclei) is a membrane-bound organelle found in eukaryotic cells.Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many.
The centrosome is copied only once per cell cycle, so that each daughter cell inherits one centrosome, containing two structures called centrioles. The centrosome replicates during the S phase of the cell cycle. During the prophase in the process of cell division called mitosis, the centrosomes migrate to opposite poles of the cell. The mitotic ...
The nucleolus (/ nj uː ˈ k l iː ə l ə s, ˌ nj uː k l i ˈ oʊ l ə s /; pl.: nucleoli /-l aɪ /) is the largest structure in the nucleus of eukaryotic cells. [1] It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signal recognition particles and plays a role in the cell's response to ...