Consequently, the textbook image of a mitochondrion became that of a static and unvarying organelle marooned in the cytoplasm. However, with the advent of electron microscopy and its ability to unearth the secrets of cellular ultrastucture, the dynamic aspects of mitochondrial form were overshadowed for many years by pictures of organelles in fixed tissue samples. Alterations in mitochondrial morphology have been recorded for over 100 years, with early light microscopists describing changes in mitochondrial size, number and position under many different conditions. In keeping with the magnitude of these responsibilities, mitochondria are themselves highly regulated and dynamic organelles, having the ability to change both form and function rapidly to meet the physiological needs of the cell. Following their identification as the site of oxidative phosphorylation 60 years ago, mitochondria have also been implicated in the regulation of programmed cell death, the biosynthesis of haem complexes, calcium signalling, the oxidation of fatty acids and, more recently, as a platform for signal transduction in the innate immune response. In addition to their classic role as generators of ATP, mitochondria are central to several vital cellular functions. In the present chapter we discuss the mechanisms behind mitochondrial fission and fusion, and discuss the implications of changes in organelle morphology during the life of a cell. Although not fully understood, alterations in mitochondrial morphology appear to be involved in several activities that are crucial to the health of cells. Fission and fusion are active processes which require many specialized proteins, including mechanical enzymes that physically alter mitochondrial membranes, and adaptor proteins that regulate the interaction of these mechanical proteins with organelles. These actions occur simultaneously and continuously in many cell types, and the balance between them regulates the overall morphology of mitochondria within any given cell. Many of these changes are related to the ability of mitochondria to undergo the highly co-ordinated processes of fission (division of a single organelle into two or more independent structures) or fusion (the opposing reaction). M_\text$ "feels" maximum pull via strong force due to no one nucleon being "out of range" of another nucleon's pull.Mitochondria are highly dynamic cellular organelles, with the ability to change size, shape and position over the course of a few seconds. The stronger the binding energy per nucleon, the less mass per nucleon.Įxample for neutron, proton and them bound together in deuterium: Mass defect is directly proportional to the binding energy. average energy per nucleus is higher before the reaction and lower after the reaction.Īfter the reaction - the resulting elements are closer to the iron atomic number The surplus energy is the energy taken out of the system, i.e. The surplus energy in the nuclear reaction is achieved when heavy elements are split (fission), or light element are fused (fusion). It is abundant in the universe, as natural atomic evolution tends to get close to it from both ends of atomic number spectrum. Both the lighter and heavier elements tend to have smaller binding energy. The literature presents the binding energy chart per element, with its peak at iron (~56 nucleons). Natural systems tend to evolve to lower, not higher energy states. The more energetic a binding, the more difficult it is to break the binding, the more stable the atom made out of such bindings. The more difficult it is to split the atom, the more stable the atom is. The higher the binding energy per nucleon, the more difficult it is to split the atom. The higher the binding energy of nucleus, the more energy is stored per nucleon in the system. The stronger the nucleus is bound, the higher its binding energy. Given (1) and (2), the smaller the nucleus, the stronger it is bound. The less nucleons in a nucleus, the closer in average they are, so the strong force per each is higher and easily overcomes electromagnetic repulsion. The more nucleons in a nucleus, the bigger the nucleus is, so the average distance of a nucleon to each another is higher, hence the long-distance electromagnetic repulsion tends to overcome short-distance strong nuclear force, up to the point of occasional alpha decay in elements of transuranic end of the spectrum. Please kindly point out and explain these errors. To me, each of them seems to make sense, but some of them are contradictory, so obviously - wrong. I did some research of that topic and cannot come to a single comprehensive and consistent description.īelow are related statements I gathered or can think of, describing the problem area. What is the nature of nuclear energy? This is closely related to the correct explanation of mass defect.
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