Mitochondrion Cristae

Mitochondria are distinct organelles with two membranes. The outer membrane limits the organelle and the inner membrane is thrown into folds or shelves that project inward and are called cristae mitochondriales. The uptake of most mitochondrion-selective dyes is dependent on the mitochondrial membrane potential. Conventional fluorescent stains for mitochondria, such as rhodamine and tetramethylrosamine, are readily sequestered by functioning mitochondria. They are, however, subsequently washed out of the cells once the mitochondrion s membrane potential is lost. This characteristic limits their use in experiments in which cells must be treated with aldehyde-based fixatives or other agents that affect the energetic state of the mitochondria. To overcome this limitation, the research... 

Figure 9.1 Simple diagram of a mitochondrion showing inner and outer membranes, cristae and matrix.

Nasirudeen AM, Tan KS (2004) Isolation and characterization of the mitochondrion-like organelle from Blastocystis hominis.J Microbiol Methods 58 101-109 Painter HJ, Morrisey JM, Mather MW, Vaidya AB (2007) Specific role of mitochondrial electron transport in blood-stage Plasmodium falciparum. Nature 446 88-91 Perkins GA, Song JY, Tarsa L, Deerinck TJ, Ellisman MH, Frey TG (1998) Electron tomography of mitochondria from brown adipocytes reveals crista junctions. J Bioeneerg Biomembr 30 431-432... 

FIGURE 19-1 Biochemical anatomy of a mitochondrion. The convolutions (cristae) of the inner membrane provide a very large surface area. The inner membrane of a single liver mitochondrion may have more than 10,000 sets of electron-transfer systems (respiratory chains) and ATP synthase molecules, distributed over the membrane surface. Heart mitochondria, which have more profuse cristae and thus a much larger area of inner membrane, contain more than three times as many sets of electron-transfer systems as liver mitochondria. The mitochondrial pool of coenzymes and intermediates is functionally separate from the cytosolic pool. The mitochondria of invertebrates, plants, and microbial eukaryotes are similar to those shown here, but with much variation in size, shape, and degree of convolution of the inner membrane. 

Figure 7.1 The mitochondrion is found in all cells and contains many structures. This includes the cristae, where most ATP is produced in the final stage of cellular respiration. Being the site of ATP production, the mitochondrion is called the powerhouse of the cell.

Electron microscopy of radish radicle. Details of roots from seeds treated with 1/14-diluted reverse osmosis fraction, (a) Cortical cells showing protein-body-derived vacuoles (V) with remnants of electron-opaque protein material. Extremely swollen mitochondria (M) look like vacuoles with fine granular contents, (b) Detail of epidermal cell, showing swollen mitochondria (M), lipid droplets (L) and two dictyosomes (D). (c) The area enclosed in the rectangle in (b) is enlarged to show the two-membrane envelope and residual cristae (arrows) in a swollen mitochondrion. 

Fig. 17.6. The vectorial pumping of calcium ions and protons across the mitochondrion membranes. A schematic enlargement of the inner (cristae) membrane is shown to indicate the existence of protein-based electron (e ) and proton (H+) conduction pathways (from Ref. 26 with permission).

These organelles are the sites of energy production of aerobic cells and contain the enzymes of the tricarboxylic acid cycle, the respiratory chain, and the fatty acid oxidation system. The mitochondrion is bounded by a pair of specialized membranes that define the separate mitochondrial compartments, the internal matrix space and an intermembrane space. Molecules of 10,000 daltons or less can penetrate the outer membrane, but most of these molecules cannot pass the selectively permeable inner membrane. By a series of infoldings, the internal membrane forms cristae in the matrix space. The components of the respiratory chain and the enzyme complex that makes ATP are embedded in the inner membrane as well as a number of transport proteins that make it selectively permeable to small molecules that are metabolized by the enzymes in the matrix space. Matrix enzymes include those of the tricarboxylic acid cycle, the fatty acid oxidation system, and others. 

Mitochondria are about the size of bacteria. They have a diameter of 0.2 to 0.5 gm and are 0.5 to 7 p.m long. They are bounded by two lipid bilayers, the inner one being highly folded. These folds are called cristae. The innermost space of the mitochondrion is called the matrix. They have their own DNA in the form of at least one copy of a circular double helix (Chap. 7), about 5 p.m in overall diameter it differs from nuclear DNA in its density and denaturation temperature by virtue of being richer in guanosine and cytosine (Chap. 7). The different density from nuclear DNA allows its separation by isopycnic centrifugation. Mitochondria also have their own type of ribosomes that differ from those in the cytoplasm but are similar to those of bacteria. 

Figure 17.1. Mitochondrion. The double membrane of the mitochondrion is evident in this electron micrograph. The numerous invaginations of the inner mitochondrial membrane are called cristae. The oxidative decarboxylation of pyruvate and the sequence of reactions in the citric acid cycle take place within the matrix. [(Left) Omikron/Photo Researchers.]...

Each mitochondrion (plural mitochondria) is bounded by two membranes (Figure 2.24a). The smooth outer membrane is relatively porous, because it is permeable to most molecules with masses less than 10,000 D. The inner membrane, which is impermeable to ions and a variety of organic molecules, projects inward into folds that are called cristae (singular crista). Embedded in this membrane are structures composed of molecular complexes and called respiratory assemblies (described in Chapter 10) that are responsible for the synthesis of ATP. Also present are a series of proteins that are responsible for the transport of specific molecules and ions. 

A FIGURE 5-26 Electron micrograph of a mitochondrion. Most ATP production in nonphotosynthetic cells takes place in mitochondria. The inner membrane, which surrounds the matrix space, has many infoldings, called cristae. Small calcium-containing matrix granules also are evident. [From D. W. Fawcett, 1981, The Cell, 2d ed., Saunders, p. 421.]... 

The mitochondrial inner membrane, cristae, and matrix are the sites of most reactions involving the oxidation of pyruvate and fatty acids to CO2 and H2O and the coupled synthesis of ATP from ADP and Pj. These processes Involve many steps but can be subdivided into three groups of reactions, each of which occurs in a discrete membrane or space in the mitochondrion (Figure 8-7) ... 

The actual site in the mitochondrion where ATP is made is Complex V (also called ATP synthase or the FOFl complex). It is located on the inner mitochondrial cristae and has the structure shown in Figure 15.14. 

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