Cristae membrane of mitochondria

Fig. 5.5. Scheme of a possible arrangement of four electron transport complexes in the cristae membrane of mitochondria. (FeS), (FeS)s, and (FeS) symbolize the nonhaem Fe-S centers of the Green complexes 1, 2, and 3, respectively FMN is flavinmono-nucleotide FAD is flavinadenindinucleotide Cj is cytochrome c c is cytochrome c a and are the cytochrome a and of the cytochrome oxidase complex. 

Cristae Tightly folded inner membranes of mitochondria where ATP is made. 

In previous papers, we proved that the photophosphorylation could be proceeded in the combination of the deficient thylakoid membranes from spinach chloroplasts with the crista membranes from mitochondria (1. 2), and that the electron transport of such combined system was linked together (2. 3) the possible electron pathways... 

In thermodynamics, one deals with closed and open systems, the difference between the two being that the latter involves the exchange of matter in addition to energy (heat and work), Clearly, a cell is an open system. Similarly, organelles such as chloroplasts and mitochondria are also open systems. Other energy transducing systems of interest are found in bacteria, in visual receptors. We shall mainly focus out attention on the thylakoid membrane of chloroplasts and the cristae membrane of rnito-chondria. It is particularly noteworthy that energy transduction and material transport in these two systems are coupled the products of photosynthesis are utilized as the reactants in respiration, and vice versa. 

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. 

In eukaryotic cells, electron transport and oxidative phosphorylation occur in mitochondria. Mitochondria have both an outer membrane and an inner membrane with extensive infoldings called cristae (fig. 14.2). The inner membrane separates the internal matrix space from the intermembrane space between the inner and outer membranes. The outer membrane has only a few known enzymatic activities and is permeable to molecules with molecular weights up to about 5,000. By contrast, the inner membrane is impermeable to most ions and polar molecules, and its proteins include the enzymes that catalyze oxygen consumption and formation of ATP. The role of mitochondria in 02 uptake, or respiration, was demonstrated in 1913 by Otto Warburg but was not fully confirmed until 1948, when Eugene Kennedy and Albert Lehninger showed that mitochondria carry out the reactions of the TCA cycle, the transport of electrons to 02, and the formation of ATP. 

The lattice-like membrane arrangement of the cristae of mitochondria in the giant amoeba was interpreted by Pappas and Brandt [22] to be composed of membranous tubules. If instead of discrete tubules, a continuous surface is assigned in such a way that it links the sections, a cubic membrane can be... 

Pronounced mitochondria swelling with loss of cristae, development of amorphous matrix densities, and breaks in the sarcolemma are seen in irreversibly injured myocytes. Increased mitochondrial size is an early indication of ischemia. In hearts with 3-15 min of ischemia, morphologic injury is reversible, yet some mitochondria remain swollen even at 20 min of reperfusion. Therefore, a majority of the mitochondria in the ischemic myocardium is expected to be edematous at 30 min of reperfusion. However, early CSIL treatment of ischemic hearts (I and 5 min) results in normal mitochondrial size, smaller than that of CSIL-treated hearts at later times (35). Cessation of mitochondrial electron transport has been observed 2 s after the onset of global ischemia in isolated rat hearts (36). The results of mitochondrial size determination are compatible with the delay in the recovery of function with later administration of CSIL. Thus, mitochondrial ultra-structural data agree with the functional and histochemical data. Preservation of cell membrane integrity after CSIL intervention results in a faster recovery of function and a reduction in infarct size. Whether this is associated with prevention of the influx of extracellular Ca that is associated with ischemia and reperfusion is not assessed in our studies. However, uncontrolled influx of Ca into the cytosol occurs after reperfusion and results in rigor (37, 38). 

The cristae greatly expand the surface area of the inner mitochondrial membrane, enhancing its ability to generate ATP (see Figure 8-6). In typical liver mitochondria, for example, the area of the inner membrane including cristae is about five times that of the outer membrane. In fact, the total area of all inner mitochondrial membranes in liver cells is about 17 times that of the plasma membrane. The mitochondria in heart and skeletal muscles contain three times as many cristae as are found in typical liver mitochondria— presumably reflecting the greater demand for ATP by muscle cells. 

Dudkina, N.V., Sunderhaus, S., Braun, H.P. and Boekema, E.J., Characterization of dimeric ATP synthase and cristae membrane ultrastructure from Saccharomyces and Polytomella mitochondria, FEBS Lett 580 (2006) 3427-3432. 

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