Outer membrane mitochondria

Monoamine oxidase and aryl-ester hydrolase are marker enzymes of mitochondria (outer membranes) and microsomes, respectively. Values are expressed as nmol / min per mg protein and are means S.E.M (n. (X)4 4)... 

The mitochondrion has an outer and an inner membrane (Figure 1). The outer membrane contains pores formed from a protein, porin, which allow exchange of molecules with molecular weights up to about 2,000 between the cytosol and the intermembrane space. The inner membrane is extensively invaginated to increase its surface area. It has a different lipid composition from the outer membrane and is rich in the acidic phospholipid cardiolipin (diphosphatidyl-glycerol) which is only found in animal cells in mitochondria. Cardiolipin confers good electrical insulating properties on the inner membrane which is impermeable... 

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... 

What do I mean by a proton concentration gradient Simply, there is a higher concentration of protons in the space between the inner and outer membranes of the mitochondrion than in the mitochondrial interior. The gradient is formed from the energy released in the transfer of electrons down the electron transport chain. Put another way, the released energy is employed to pump protons across the inner mitochondrial membrane into the intermembrane space. 

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

One of the most puzzling structures within C. parvum sporozoites, is the crystalloid body (CB), which is also in intimate contact with the relic mitochondrion, outer nuclear membrane, and RER (Fig. 1) (Keithly et al. 2005). Although it is still unclear whether this organelle is surrounded by a limiting membrane, or is simply a complex of closely packed membrane-bounded vesicles, it has been shown that like the relic mitochondrion, the CB takes up mitotracker dyes (Ctrnacta et al. 2006 Kayser et al. 2002 Keithly et al. 

FIGURE 21-10 Shuttle for transfer of acetyl groups from mitochondria to the cytosol. The mitochondrial outer membrane is freely permeable to all these compounds. Pyruvate derived from amino acid catabolism in the mitochondrial matrix, or from glucose by glycolysis in the cytosol, is converted to acetyl-CoA in the matrix. Acetyl groups pass out of the mitochondrion as citrate in the cytosol they are de-... 

Structure of the mitochondrion The components of the electron transport chain are located in the inner membrane. Although the outer membrane contains special pores, making it freely perme-... 

Mitochondria are intracellular centers for aerobic metabolism. They are cell organelles that are identified by well-defined structural and biochemical properties. In morphological terms, mitochondria are relatively large particles that are characterized by the presence of two membranes, a smooth outer membrane that is permeable to most important metabolites and an inner membrane that has unique transport properties. The inner membrane is highly folded, which serves to increase its surface area. Figure E10.1, which shows the structure of a typical mitochondrion, divides the organelle into four major components inner membrane, outer membrane, intermembrane space, and the matrix. These regions are associated with different and... 

This reaction is catalyzed by carnitine acyltransferase I on the outer membrane (fig. 18.21). A protein carrier in the inner mitochondrial membrane transfers the acyl-carnitine derivatives across the membrane. Once inside the mitochondria, the reaction is reversed by carnitine acyltransferase II to yield a fatty acyl-CoA (see fig. 18.21). Thus, at least two distinct pools of acyl-CoA occur in the cell, one in the cytosol and the other in the mitochondrion. 

Mitochondria A mitochondrion has an inner and an outer membrane between which is the... 

Cells must ensure that each newly synthesized protein is sorted to its correct location where it can carry out the appropriate function. This process is called protein targeting. In a eukaryotic cell, the protein may be destined to stay in the cytosol, for example an enzyme involved in glycolysis (see Topic J3). Alternatively it may need to be targeted to an organelle (such as a mitochondrion, lysosome, peroxisome, chloroplast or the nucleus) or be inserted into the plasma membrane or exported out of the cell. In bacteria such as E. coli, the protein may stay in the cytosol, be inserted into the plasma membrane or the outer membrane, be sent to the space between these two membranes (the periplasmic space) or be exported from the cell. In both prokaryotes and eukaryotes, if a protein is destined for the cytosol, it is made on free ribosomes in the cytosol and released directly into the cytosol. If it is destined for other final locations, specific protein-targeting mechanisms are involved. 

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 release not only cytochrome c but also many pro-apoptotic factors (Table 17.1). They are normally localized in the intermembrane space of mitochondria. However, except for cytochrome c and the apoptosis inducing factor (AIF), their functions in the mitochondria have not been determined or they may have no function under normal conditions. Because they are larger than 5kD, they remain inside the mitochondrion. Once the mitochondrial outer membrane is permeabi-... 

Siskind LJ, Kolesnick RN, Colombini M. Ceramide forms channels in mitochondrial outer membranes at physiologically relevant concentrations. Mitochondrion 2006 6 118-125. 

The mitochondrion is bounded by two pho-spholipid membranes. The outer membrane is freely permeable to molecules, including water, with a molecular weight of up to about 5000. The inner membrane is rich in membrane-bound proteins and consists, in terms of membrane area, of 50% phospholipid and 50% protein (Lenaz, 1988). Pyruvate dehydn>genase, a mitochondrial enzyme, is water soluble. The proteins of the respiratory chain, as well as ATP synthase, are all bound to the inner mitochondrial membrane. The enzymes of the Krebs cycle are water soluble, with the exception of succinate dehydrogenase. This enzyme is bound to the mitochondrial membrane, where it directly funnels electrons, via HAD, to the respiratory chain. 

Actively respiring fungal cells possess a distinct mitochondrion, which has been described as the power-house of the cell (Fig. 4.2). The enzymes of the tricarboxylic acid cycle (Kreb s cycle) are located in the matrix of the mitochondrion, while electron transport and oxidative phosphorylation occur in the mitochondrial inner membrane. The outer membrane contains enzymes involved in lipid biosynthesis. The mitochondrion is a semiindependent organelle as it possesses its own DNA and is capable of producing its own proteins on its own ribosomes, which are referred to as mitoribosomes. 

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