Organelles mitochondrion

Lipid peroxidation is probably the most studied oxidative process in biological systems. At present, Medline cites about 30,000 publications on lipid peroxidation, but the total number of studies must be much more because Medline does not include publications before 1970. Most of the earlier studies are in vitro studies, in which lipid peroxidation is carried out in lipid suspensions, cellular organelles (mitochondria and microsomes), or cells and initiated by simple chemical free radical-produced systems (the Fenton reaction, ferrous ions + ascorbate, carbon tetrachloride, etc). In these in vitro experiments reaction products (mainly, malon-dialdehyde (MDA), lipid hydroperoxides, and diene conjugates) were analyzed by physicochemical methods (optical spectroscopy and later on, HPLC and EPR spectroscopies). These studies gave the important information concerning the mechanism of lipid peroxidation, the structures of reaction products, etc. 

Eukaryotic cells also have organelles, mitochondria (Fig. 24-6) and chloroplasts, that contain DNA. Mitochondrial DNA (mtDNA) molecules are much smaller than the nuclear chromosomes. In animal cells, mtDNA contains fewer than 20,000 bp (16,569 bp in human mtDNA) and is a circular duplex. Each mitochondrion typically has two to ten copies of this mtDNA molecule, and the number can rise to hundreds in certain cells when an embryo is undergoing cell differentiation. In a few organisms (trypanosomes, for example) each mitochondrion contains thousands of copies of mtDNA, organized into a complex and interlinked matrix known as a kinetoplast. Plant cell mtDNA ranges in size from... 

Eukaryotes have various DNA molecules, arranged in linear fibers which are repeatedly coiled and folded to produce highly organised chromosomes, and a composite cytoplasm which is divided into distinct compartments and houses a variety of cell organelles (mitochondria, chloroplasts, lysosomes, the endoplasmic reticulum, etc.) the form of the cell is due to an internal cytoskeleton which is made of three different types of filaments (microtubules, microfilaments and intermediate filaments). 

Iron damages hepatocellular organelles. Mitochondria exposed to excessive iron show increased fragility, increased volume, increased pH, decreased fluidity, and increased lipid peroxidation (Britton, 1996). Lysosomes exposed to iron overload show increased fragility and... 

Many tiny strnctures reside in the cytoplasm (the liqnid interior) of the cell these organelles are responsible for making proteins and other substances that enable the cell to do its job. Other organelles (mitochondria) provide energy to other cell parts. Without healthy mitochondria, cells cannot function. For example, in a nerve cell (a neuron see Figure 1.2) there are components that make chemicals called neurotransmitters, which allow one neuron to transmit an impulse to another. 

Eukaryotic cells have many separate organelles. Mitochondria are the site of ATP synthesis nuclei contain most of the nucleic acid of eukaryotic cells, including the chromosomes the endoplasmic reticulum divides the cell into different topological domains. 

Naturally, uncoupling compounds have been identified to include nonesterified fatty acids forms in which palmitic acid could be one of them (Borst et al., 1962 Pressman Lardy, 1956 Wojtczak Lehninger, 1961). Further evidence, on fatty acid been accumulated in larger amounts inside or trapped by any isolated mitochondria has been reported to be responsible for poor P/0 ratios in aged rat liver mitochondria (Chefurka Dumas, 1966). These fatty acids turn to create swelling of tlie organelle (Mitochondria) resulting in... 

In eukaryotes, oxidative phosphorylation occurs in mitochondria, while photophosphorylation occurs in chloroplasts to produce ATP. Oxidative phosphorylation involves the reduction of O2 to H2O with electrons donated by NADH and FADH2 in all aerobic organisms. After, carbon fuels (nutrients) are oxidized in the citric acid cycle, electrons with electron-motive force is converted into a proton-motive force. Photophosphorylation involves the oxidation of H2O to O2, with NADP as electron acceptor. Therefore, the oxidation and the phosphorylation of ADP are coupled by a proton gradient across the membrane. In both organelles, mitochondria and chloroplast electron transport chains pump protons across a membrane from a low proton concentration region to one of high concentration. The protons flow back from intermembrane to the matrix in mitochondria, and from thylakoid to stroma in chloroplast through ATP synthase to drive the synthesis of adenosine triphosphate. Therefore, the adenosine triphosphate is produced within the matrix of mitochondria and within the stroma of chloroplast. 

Lipid Plasmalemma Whole organelle Mitochondria" Inner Outer membranes membranes Peroxisome Microsome ... 

To determine which organelles were involved in lipid synthesis, plant cell organelles (mitochondria, microsomes, peroxisomes, plasmalemma, nuclei) were isolated in vitro and fed with various radioactive precursors ([ C]ace-tate or [ C]acetyl-CoA, [ K ]malonate or [ K ]malonyl-CoA, [ P]phos-phate, [ C]glycerol or [ K]l]glycerophosphate, [ C]choline or [ CJethanola-mine, etc.). The biosynthetic capacities of each organelle were thus evidenced (see Mazliak, 1975, 1977) in an effort to locate the sites of lipid synthesis in plant cells. The following points appeared clearly from the experiments ... 

Fatty acid" Plasmalemma" Whole organelles Mitochondria Inner membranes 1 Outer membranes Peroxisomes Microsomes ... 

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