Mitochondrion - Wikipedia
mitochondria and chloroplasts are thought to have resulted from ancestral endosymbiotic relationships between nucleated cells and free .. particular meme. Keywords: Arabidopsis, mitochondria, chloroplasts, retrograde, stress . in the Multiexperiment Viewer MeV using the Pearson correlation coefficient. The MEME suite was then used to discover overrepresented motifs in. Structure and function of mitochondria and chloroplasts. scientists think host cells and bacteria formed endosymbiotic relationships long ago, when individual .
These folds are studded with small round bodies known as F1 particles or oxysomes.
Mitochondria and Chloroplasts
These are not simple random folds but rather invaginations of the inner membrane, which can affect overall chemiosmotic function. Mitochondrial matrix The matrix is the space enclosed by the inner membrane. The matrix contains a highly concentrated mixture of hundreds of enzymes, special mitochondrial ribosomestRNAand several copies of the mitochondrial DNA genome.
Of the enzymes, the major functions include oxidation of pyruvate and fatty acidsand the citric acid cycle. Mitochondria associated membranes MAM The mitochondria-associated ER membrane MAM is another structural element that is increasingly recognized for its critical role in cellular physiology and homeostasis. Once considered a technical snag in cell fractionation techniques, the alleged ER vesicle contaminants that invariably appeared in the mitochondrial fraction have been re-identified as membranous structures derived from the MAM—the interface between mitochondria and the ER.
Not only has the MAM provided insight into the mechanistic basis underlying such physiological processes as intrinsic apoptosis and the propagation of calcium signaling, but it also favors a more refined view of the mitochondria. Though often seen as static, isolated 'powerhouses' hijacked for cellular metabolism through an ancient endosymbiotic event, the evolution of the MAM underscores the extent to which mitochondria have been integrated into overall cellular physiology, with intimate physical and functional coupling to the endomembrane system.
Phospholipid transfer The MAM is enriched in enzymes involved in lipid biosynthesis, such as phosphatidylserine synthase on the ER face and phosphatidylserine decarboxylase on the mitochondrial face. In particular, the MAM appears to be an intermediate destination between the rough ER and the Golgi in the pathway that leads to very-low-density lipoproteinor VLDL, assembly and secretion. One of its components, for example, is also a constituent of the protein complex required for insertion of transmembrane beta-barrel proteins into the lipid bilayer.
Other proteins implicated in scaffolding likewise have functions independent of structural tethering at the MAM; for example, ER-resident and mitochondrial-resident mitofusins form heterocomplexes that regulate the number of inter-organelle contact sites, although mitofusins were first identified for their role in fission and fusion events between individual mitochondria.
Coupling between these organelles is not simply structural but functional as well and critical for overall cellular physiology and homeostasis.
The MAM thus offers a perspective on mitochondria that diverges from the traditional view of this organelle as a static, isolated unit appropriated for its metabolic capacity by the cell. Instead, this mitochondrial-ER interface emphasizes the integration of the mitochondria, the product of an endosymbiotic event, into diverse cellular processes.
Organization and distribution Typical mitochondrial network green in two human cells HeLa cells Mitochondria and related structures are found in all eukaryotes except one—the Oxymonad Monocercomonoides sp.
The compartmentalization of the mitochondrion into matrix and intermembrane space is essential for oxidative phosphorylation, as it allows a proton gradient to be established. These electrons are captured by special molecules called electron carriers and deposited into the electron transport, a series of proteins embedded in the inner mitochondrial membrane. For instance, muscle cells typically have high energy needs and large numbers of mitochondria, while red blood cells, which are highly specialized for oxygen transport, have no mitochondria at all.
The Evolution of the Cell
Both mitochondria and chloroplasts contain their own DNA and ribosomes. Strong evidence points to endosymbiosis as the answer to the puzzle.
Symbiosis is a relationship in which organisms from two separate species live in a close, dependent relationship. The first endosymbiotic event occurred: The ancestral eukaryote consumed aerobic bacteria that evolved into mitochondria. In a second endosymbiotic event, the early eukaryote consumed photosynthetic bacteria that evolved into chloroplasts. Bacteria also have DNA and ribosomes similar to those of mitochondria and chloroplasts.
Through millions of years of evolution, the aerobic bacteria became mitochondria and the photosynthetic bacteria became chloroplasts. Attribution and references Attribution: Download the original article for free at http: The relevance of mitochondrial membrane topology to mitochondrial function. Retrieved December 20, from Wikipedia: Retrieved July 20, from Wikipedia: A tour of the cell. In Biology 8th ed. Retrieved August 10, from Wikipedia: Red algal genome affirms a common origin of all plastids.
Current Biology, 14 13RR In Biology 10th ed. Therefore, several mutants in specifically chloroplast of mitochondrial proteins were examined. Furthermore, the expression of genes that responded significantly to these organellar perturbations was examined across a wide variety of developmental and stress-related microarray experiments to allow a better picture of how retrograde responses are situated within the lifecycle of a plant.
Materials and Methods Generation of organelle-specific gene lists Genes encoding chloroplast, mitochondrial or peroxisome proteins were selected based on publicly available information based on mass-spectrometry, Green Fluorescent Protein-targeting assays, and subcellular localization prediction algorithms. The list for mitochondria was taken from a previous study Law et al.
In this way genes were selected and in total probe sets represented genes in this list on the Affymetrix ATH1 GeneChip microarrays.
Similarly, SUBA was used as a starting point for peroxisomal proteins and genes for which predicted two or more of the 10 prediction algorithms localization in peroxisomes was evidenced were selected. Proteins reported by several proteomic studies were also included Reumann et al. In total genes encoding peroxisomal proteins were selected and in total probe sets represented genes in this list on the Affymetrix ATH1 GeneChip. All gene lists are shown in Table S1 in Supplementary Material.
Microarray data analysis For the datasets related to chloroplast and mitochondrial perturbations CEL files were normalized using the MAS5. Probe sets that were not called absent in at least half of the chips for one genotype or treatment were kept for further analysis.