Most vertebrate muscles have Sv(im,mt) values between 20 and 40 m2 of inner mitochondrial membrane per cubic centimeter of mitochondria. The reason for this is probably related to constraints on intramitochondrial dimensions and diffusion distances. When inner membrane is packed this tightly, there is barely enough room for a couple of enzyme molecules between opposing layers of inner membrane. The fact that this basic design feature of muscle mitochondria is similar across broad taxa infers that the main way animals alter OXPHOS capacity is by changing the volume of mitochondria within the fiber. However, there are a few high-performance species of vertebrates – tuna, hummingbird, and pronghorn antelope – that have been shown to possess mitochondria with surface area to volume ratios that are twice as high, in the 60–70 m2 cm−3 range. It is thought that this elevated surface area is an important mechanism by which these species increase OXPHOS capacity within the muscle. Conversely, some polar fish have very low inner-membrane surface area (< 20 m2 cm−3), though mitochondrial content is relatively normal. Recall that mitochondria in muscle occur as a reticulum and it is thought that this arrangement of mitochondria – abundant mitochondria with relatively few cristae – facilitates diffusion of oxygen into the depths of the muscle. Show View chapterPurchase book Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780123745538002719 Myopathy, MitochondrialM. Hirano, in Encyclopedia of the Neurological Sciences (Second Edition), 2014 Defects of the mitochondrial lipid milieu compositionThe inner mitochondrial membrane (IMM) contains phospholipids that are critical for the structure and integrity of the embedded respiratory chain proteins. Barth's syndrome is a prototypical disorder of mitochondrial phospholipid metabolism with secondary respiratory chain defects. This X-linked recessive disorder is caused by mutations in TAZ1, encoding the monolysocardiolipin transacylase, which is required for cardiolipin remodeling. The disease is characterized clinically by mitochondrial cardiac and skeletal myopathy, cyclic neutropenia, and growth retardation with defects of respiratory chain enzyme activities. A second disorder of the mitochondrial lipid mileu is an autosomal recessive congenital myopathy with mental retardation and a protracted course. The cause is mutations in CHKB, encoding choline kinase beta, an enzyme required for the de novo synthesis of phosphatidyl choline and phosphatidylethanolamine. Muscle biopsies have revealed a strikingly enlarged mitochondria that were displaced to the periphery of the fibers. Sengers syndrome, an autosomal recessive disease that presents with congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy, exercise intolerance, and lactic acidosis, is due to mutations in the AGK gene encoding acylglycerol kinase. The AGK defect causes deficiency of phosphatidic acid and secondary decrease of ANT in the IMM.  Understanding: • The structure of the mitochondrion is adapted to the function it performs
Structure and Function of a Mitochondrion Skill: • Annotation of a diagram of a mitochondrion to indicate the adaptations to its function Typically, mitochondrial diagrams should display the following features:
Mitochondrion Diagrams ⇒ Click on the diagram to show / hide labels Application: • Electron tomography used to produce images of active mitochondria
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Which part of the mitochondrion contains the proteins that carry out oxidative phosphorylation?
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