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# In chemistry and physics, the term used to describe that collection of protons and neutrons in the center of an atom that carry the bulk of the atoms mass and positive charge. |
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# In biology, nucleus refers to the membrane-bound subcellular organelle found in eukaryotes, visible via microscopy, which contains, primarily, the cell's chromosomes. The biological nucleus has two main functions: * to control chemical reactions in the cell cytoplasm * to store information needed for when the cell divides The nucleus controls reactions by controlling the formation of proteins and enzymes. Structure The nucleus varies in diameter from 10 to 20 micrometres. It is surrounded by a double membrane forming the nuclear envelope, about 30 nm wide. This selectively allows molecules to enter and leave the nucleus, and separates chemical reactions taking place in cytoplasm from reactions happening within the nucleus. The outer membrane has ribosone?s. The inner and outer membrane fuse at regular spaces, forming nuclear pores. Similar to the cytoplasm of a cell, the nucleus contains nucleoplasm? - a highly viscous liquid containing the chromosones and nucleoli?. Chromosones contain information encoded in DNA attached to proteins called histones and are usually arranged in to a dense network called a chromatin. Nucleoli are granular structures which make rionucleic-DNA (rDNA) and put together proteins. |
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# In chemistry and physics, the term used to describe that collection of protons and neutrons in the center of an atom that carry the bulk of the atoms mass and positive charge. See [atomic nucleus]?. # In biology, nucleus refers to the membrane-bound subcellular organelle found in eukaryotes, visible via microscopy, which contains, primarily, the cell's chromosomes. See cell nucleus. # In astronomy, the solid core of a comet is referred to as the comet's nucleus. |
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