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A model of an atomic nucleus showing it as a compact bundle of protons (red) and neutrons (blue), the two types of nucleons.In this diagram, protons and neutrons look like little balls stuck together, but an actual nucleus (as understood by modern nuclear physics) cannot be explained like this, but only by using quantum mechanics.
The atomic nucleus is a bound system of protons and neutrons. The spatial extent and shape of the nucleus depend not only on the size and shape of discrete nucleons, but also on the distance between them (the inter-nucleon distance). (Other factors include spin, alignment, orbital motion, and the local nuclear environment (see EMC effect).)
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 .
Outside the nucleus, free neutrons undergo beta decay with a mean lifetime of about 14 minutes, 38 seconds, [24] corresponding to a half-life of about 10 minutes, 11 s. The mass of the neutron is greater than that of the proton by 1.293 32 MeV/ c 2 , [ 25 ] hence the neutron's mass provides energy sufficient for the creation of the proton ...
For example, it requires only 13.6 eV to strip a ground-state electron from a hydrogen atom, [54] compared to 2.23 million eV for splitting a deuterium nucleus. [55] Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either a deficit or a surplus of electrons are called ions. Electrons that are ...
The main distinguishing feature of eukaryotes as compared to prokaryotes is compartmentalization: the presence of membrane-bound organelles (compartments) in which specific activities take place. Most important among these is a cell nucleus, [2] an organelle that houses the cell's DNA. This nucleus gives the eukaryote its name, which means ...
Furthermore, the energy needed to excite the nucleus (i.e. moving a nucleon to a higher, previously unoccupied level) is exceptionally high in such nuclei. Whenever this unoccupied level is the next after a full shell, the only way to excite the nucleus is to raise one nucleon across the gap, thus spending a large amount of energy. Otherwise ...
The count of nuclear pore complexes varies across cell types and different stages of the cell's life cycle, with approximately 1,000 NPCs typically found in vertebrate cells. [12] The human nuclear pore complex (hNPC) is a substantial structure, with a molecular weight of 120 megadaltons (MDa). [ 13 ]