Chloroplasts and Mitochondria: Similarities and Differences
Abstract
Eukaryotic cells contain two organelles originally derived from endosymbiotic bacteria: mitochondria and plastids (only plants). In eukaryotes, (owner mitochondria and chloroplast) ATP synthase complex is located in the inner membrane of mitochondria, and thylakoids membrane of chloroplast. ATP synthesis utilization and provision of both ADP and Pineed to be fine – tuned for optimal ATP synthase activity. Mitochondria and chloroplast have their DNA. The vast majority of mitochondrial and plastid proteins are encoded in the nucleus, synthesized by cytosolic ribosomes and subsequently imported into the organelles via active protein transport systems.
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Introduction
Several proposals have been made to explain the rise of multicellular life forms. An internal environment can be created and controlled, germ cells can be protected in novel structures, and increased organismal size allows a „„division of labor‟‟ among cell types. These proposals describe advantages of multicellular versus unicellular organisms at levels of organization at or above the individual cell. It have been focused on a subsequent phase of evolution, when multicellular organisms initiated the process of development that later became the more complex embryonic development found in animals and plants. The advantage here is realized at the level of the mitochondria and chloroplast [20].
Eukaryotic cells have chloroplast and mitochondria that both are membrane bound organelles. Prokaryotic cells, for example, bacteria have not chloroplast and mitochondria. Mitochondria occur in the cells of animals and plants but chloroplast only occur in the photosynthesising tissues of plants. These two organelles are best known for their roles in energy metabolism, notably respiration and photosynthesis [85].
Respiration occurs in mitochondria. Mitochondria were originally identified as the site of oxidative energy metabolism [13]. Mitochondria are also the host for enzymes of the Krebs cycle and β – oxidation of fatty acids. In today‟sworld mitochondria are known not only as the “power station” of the cell, but also for playing a vital role in the transmission of extra – and intracellular signals that activate reaction cascades leading to cellular senescence and programmed cell death (PCD) [104]. The discovery of a number of human diseases associated with mitochondrial dysfunctions once again brought mitochondria into the spotlight of biological research.
Chloroplasts are members of a class of plant cell organelles known as plastids that all originate from protoplastids. During plant development the protoplastids differentiate to form three major groups of plastids, the green chloroplasts, the colored chromoplasts and the colorless leucoplasts. The most abundant and important plastids are the chloroplasts. Chloroplasts harvest energy from sunlight to split water and fix carbon dioxide to produce sugars. This process called photosynthesis also converts harvested solar energy into a conserved form of energy: ATP and NADPH through a complex set of processes.
Conclusion
Chloroplasts and mitochondria are both membrane bound organelles of eukaryotic cells. They do not occur in prokaryotic cells, for example, bacteria. Mitochondria occur in the cells of animals and plants but chloroplasts only occur in the photosynthesising tissues of plants.
Chloroplasts are concerned with the process of photosynthesis whereas mitochondria are concerned with aerobic respiration. It is clear that one of the most important products of these two povital process is ATP. ATP synthesis is the central bioenergetic engine of all organisms and represents the smallest molecular motor, which was optimized in the course of evolution. In eukaryotes, the ATP synthase complex is located in the inner membrane of mitochondria, with ATP synthesis reaction occurring on the membrane side toward matrix compartment.
In plants, the enzyme is in addition localized in the thylakoid membrane of chloroplasts, with the ATP – forming – moiety facing the stroma. So we observe that there are topological differences between the mitochondrial and chloroplastic ATP synthases. Also magnesium is a important element in ATP synthesis. The role of its, is to form of Mg2+ which acts as separate substrate in the ATP synthas. It has also been shown that DNA mitochondria chloroplast has its own and that the DNA in both mitochondria and chloroplasts can be extremely unstable. Most information on the repair of mtDNA comes from yeast and somatic cells of mammals, whereas very little is known about mtDNA repair in plants or about cpDNA repair.
An ambiguous dual targeting peptide is a tool for importing one gene product into both mitochondria and chloplast. The first protein shown to be dually targeted to mitochondria and chloroplasts was glutathione reductase (GR) from Pisum sativum. It has been proposed that the information for organellar targeting can be organized in domains.
A protein domain is a conserved part of a given protein sequence and (tertiary) structure that can evolve, function, and exist independently of the rest of the protein chain.