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The size of the nucleus is correlated to the size of the cell, and this ratio is reported across a range of cell types and species. [9] In eukaryotes the nucleus in many cells typically occupies 10% of the cell volume. [10]: 178 The nucleus is the largest organelle in animal cells.
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, if the highest occupied energy level lies in a partly filled shell, much less energy is required to raise a nucleon to a higher state in the same shell.
All protons in the same level (n) have the same parity (either +1 or −1), and since the parity of a pair of particles is the product of their parities, an even number of protons from the same level (n) will have +1 parity. Thus, the total angular momentum of the eight protons and the first eight neutrons is zero, and their total parity is +1.
The nucleus is spherical and separated from the cytoplasm by a double membrane called the nuclear envelope, space between these two membrane is called perinuclear space. The nuclear envelope isolates and protects a cell's DNA from various molecules that could accidentally damage its structure or interfere with its processing.
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).)
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 hierarchical structure through which DNA is packaged into chromosomes. The organization of DNA within the nucleus begins with the 10 nm fiber, a "beads-on-a-string" structure [24] made of nucleosomes connected by 20-60bp linkers.
The nuclear pore complex (NPC) is a crucial cellular structure with a diameter of approximately 120 nanometers in vertebrates. Its channel varies from 5.2 nanometers in humans [14] to 10.7 nm in the frog Xenopus laevis, with a depth of roughly 45 nm. [15]