Mitochondria development

Mitochondria develop in the spermatid to provide the energy that is needed to sustain life and complete fertilization. 

Fig. 2.6 The moqjhological events of sporulation in Saccharomyces cerevisiae. (a) starved cell V, vacuole LG, lipid granule ER, endoplasmic reticulum CW, cell wall M, mitochondrion S, spindle pole SM, spindle microtubules N, nucleus NO, nucleolus, (b) Synaptonemal complex (SX) and development of polycomplex body (PB) along with division of spindle pole body in (c). (d) First meiotic division which is completed in (e). (f) Prepararation for meiosis II. (g) Enlargement of prospore wall, culminating in enclosure of separate haploid nuclei (h). (i) Spore coat (SC) materials produced and deposited, giving rise to the distinct outer spore coat (OSC) seen in the completed spores of the mature ascus (j). Reproduced from the review by Dickinson (1988) with permission from Blackwell Science Ltd.

DNA, mitochondrial (mt-DNA) A double-stranded molecule of DNA that controls the development and functioning of the mitochondrion containing it mt-DNA is passed along female lines. 

The cell organellae in woody plants are the nucleus, mitochondrion, rough-endoplasmic reticulum (r-ER), smooth endoplasmic reticulum (s-ER), Golgi-body, plastid, vacuole, microbody, etc. Their functions are very complicated, and some have definite roles in the biosynthesis of cell-wall components. Hence, changes in size of cell organellae are likely to occur, since cell-wall composition depends upon the stage of wall development. 

Physiologically iron entering the developing erythrocyte is transferred to the mitochondrion where it is incorporated into a tetrapyrole synthesized from amino acids to form haem. This complex then returns to the cytoplasm where it is inserted into the globin molecule to make the red iron-transporting pigment called haemoglobin. 

Calcium levels are believed to be controlled in part at least by the uptake and release of Ca2+ from mitochondria.172"174 The capacity of mitochondria for Ca2+ seems to be more than sufficient to allow the buffering of Ca2+ at low cytosol levels. Mitochondria take up Ca2+ by an energy-dependent process either by respiration or ATP hydrolysis. It is now agreed that Ca2+ enters in response to the negative-inside membrane potential developed across the inner membrane of the mitochondrion during respiration. The uptake of Ca2+ is compensated for by extrusion of two H+ from the matrix, and is mediated by a transport protein. Previous suggestions for a Ca2+-phosphate symport are now discounted. The possible alkalization of the mitochondrial matrix is normally prevented by the influx of H+ coupled to the influx of phosphate on the H - PCV symporter (Figure 10). This explains why uptake of Ca2+ is stimulated by phosphate. Other cations can also be taken up by the same mechanism. 

Is there an acceptable proposal by which this intermediate electricity (electron flow) developed from two differentkinds of sites in the mitochondrion (see Fig. 14.41), is able to convert ADP to ATP 17 (ATP has to proceed from the mitochondrion to the nearest point at which its energy is needed, e.g., to work muscles.)... 

During acidosis, the cells of the renal tubule can respond by inserting two proteins into the apical region of the plasma membrane. (The apical part is that region that is exposed to the developing urine.) The two proteins are H,K-ATPase and H+-ATPase. H,K-ATPase, and the enzymes that act in concert with it, is better known as a component of the parietal cell where it creates stomach acid. The other proton pump of the renal tubule, which is H" -ATPase, is closely related to FoFiH" -ATPase of the mitochondrial membrane. Hence, anyone who imderstands how protons are pumped out of the mitochondrion and how stomach acid is made will clearly understand how the renal tubule can shuttle protons to the lumen of the renal tubule and into the developing urine. 

ATP synthase, localized to the cytosolic face of the bacterial membrane, would then face the matrix of the evolving mitochondrion (left) or chloroplast (right). Budding of vesicles from the inner chloroplast membrane, such as occurs during development of chloroplasts in contemporary plants, would generate the thyiakoid vesicles with the Fi subunit remaining on the cytosolic face, facing the chloroplast stroma. 

Recent studies have shown that P. falciparum also possesses a single mitochondrion during its erythrocytic stages (65,66) (Fig. 13.7). This mitochondrion enlarges and becomes multilobed as development proceeds. Eventually each daughter merozoite receives a lobe of the mitochrondrion, presumably complete with its own copy of the mitochondrial genome. 

HOS. Because R. sphaeroides is a member of the class of proteobacteria from which the mitochondrion is thought to have developed, both HOS and HAS (as well as the catalytic subunits of CcO) share a high degree of sequence homology with their eukaryotic counterparts. Thus, what we observe in R. sphaeroides may very well be more generally applicable to include eukaryotic organisms. However, no direct interaction has yet been observed in yeast between HOS and HAS despite numerous attempts, and any extrapolation between the work reported here and potential interactions between eukaryotic HOS and HAS must therefore be treated with caution. 

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