Cell , biological mitochondria

Biochemistry is a dynamic, rapidly growing field, and the goal of this color atlas is to illustrate this fact visually. The precise boundaries between biochemistry and related fields, such as cell biology, anatomy, physiology, genetics, and pharmacology, are dif cult to define and, in many cases, arbitrary. This overlap is not coincidental. The object being studied is often the same—a nerve cell or a mitochondrion, for example—and only the point of view differs. 

In the following sections we discuss each of the anaerobic groups containing mitochondrion-derived organelles in turn and outline our current understanding of their evolutionary affinities, as well as their biochemical and cell biological properties. 

Is it a tenable idea that RH (representing chemicals from the final products of digestion, such as glucose) is electrochemically converted to electricity at the mitochondrion within biological cells (Fig. 14.41) ... 

Moore then explained how mitochondria are biological fuel cells. The oxygen reduction taking place in a mitochondrion is exactly the same as in a standard fuel cell. Using several enzymes and only earth-abundant elements, the mitochondrion converts electrochemical potential to biochemical work with efficiency greater than 90 percent. This is a steady-state process in which protons are pumped across the membrane to maintain its electrical potential. If... 

Dimitrov D, Mutoh Y-H, Baker BJ, Cohen L, Akemann W, Knopfel T. Engineering and characterization of an enhanced fluorescent protein voltage sensor. PLoS ONE 2007 2 e440. Beard DA, Vendelin M. Systems biology of the mitochondrion. Am. J. Physiol. Cell Physiol. 2006 291 C1101-C1103. 

The other phases are less exotic. The mesh phases consists of lamellae with ordered holes, while ribbon phases are deformed cylinders on a rectangular lattice (see Fig. 12-22). These phases can are usually type I phases with the tails inside the deformed cylinders or inside the hole-filled lamellae, but they could also be inverse, type II, phases. Type II mesh and ribbon phases seem not to have been reported much type II strut phases are common for two-tailed lipids, such as those in cell membranes. In fact, type II strut phases evidently serve biological functions, since they have been found to exist in cellular structures such as the endoplasmic reticulum and the mitochondrion (Seddon 1996). 

Figure 18.2 Electron micrograph (A) and diagram (B) of a mitochondrion. [(A) Courtesy of George Pa lade. (B) After Biology of the Cell by Stephen L. Wolfe. 1972 by Wadsworth Publishing Company, Inc., Belmont, California 94002. Adapted by permission of the publisher]... 

It should not be assumed that hydroxy fatty acids are biologically inactive. Hydroxy fatty acids are chemotactic and vasoactive. Such fatty acids could perturb phospholipids in membranes. For instance, cardiolipin containing hydroxy-linoleic acid does not support the electron transport coupled to ATP production of the mitochondrion. 5-Hydroxy de-canoic acid is a well-known inhibitor of the K -ATP channel. Isoprostanes, trihydroxy oxidation products of arachi-donic acid, are vasoconstrictors (76). 13-Hydroxy linoleic acid (13-HODE) is a lipoxygenase-derived metabolite that influences the thromboresistant properties of endothelial cells in culture (77). However, there is some doubt about the tme nature of these hydroxy-fatty acids generated by the cells, as there are several GSH- and NADPH-dependent pathways that can immediately reduce hydroperoxy- to hydroxy-fatty acids. Furthermore, the reduction step of the analytical method would have converted the hydroperoxy- to a hydroxy-group. Nevertheless, much work remains to be done to determine the relative contribution of hydroperoxy- and hydroxy- to the biological effects of fried fat, and in particular their role in endothelial dysfunction and activation of factor VII. There have been earlier suggestions that a diet rich in lipid peroxidation products may lead to atherosclerosis and CHD (34,78). 

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