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Watch them carefully; you will see it. These are times that make ordinary men into saints or devils or both. As some of you know, the Nine Underworlds of Creation and the opening of human multidimensional awareness describe the cyclic unfolding of evolution in the Milky Way Galaxy. They must be diligently studied and mastered by as many of you as possible because comprehending this gift from the Coba Maya enables you to be self-reflective about creation itself; this enables you to find your place in the grand scheme of things.

As you do this, beings in the fifth through ninth dimensions have special badges, robes, and hats waiting for you when you identify your own role!

What could possibly be more important, since you are poised on the edge of annihilation as you become conscious of your place in the multiverse? As we see it, you are going to do it because the negative patterns of the dark forces are burning up in the sunlight; the king, queen, and the pope have no clothes.

Mochila gocase bag planetinhas manuscrita – Artofit

The mayor too! Felicitas Goodman. Ecstatic trance. Mitochondria have existed for more than a billion years, but it was not until the middle of the nineteenth century that they were actually recognised in cells, at first as a grainy appearance in the cell cytoplasm when observed by light microscopy.

In the following years, many people speculated on the role of mitochondria in the cell, with Warburg recognising the particulate nature of cell respiration and Keilin associating the cytochrome system with cellular structures. The first direct evidence for this functional association depended on isolation of the mitochondria from the rest of the cell, which became possible in the s. The first isolations of mitochondria by cell fractionation were made by Bensley and Hoerr , and, following this breakthrough, the path opened for study of the biochemical reactions occurring in mitochondria.

However the possible origin of mitochondria was not looked at for some time, not really until the s. It was in the early s that Ephrussi and Mitchell and Mitchell observed that mitochondrial replication in yeast cells was controlled by non-Mendelian genetic factors, and slightly later that McLean et al. The discovery of mitochondrial DNA followed in the early s, when a number of different groups Luck and Reich ; Nass and Nass a,b; Schatz et al.

While the endosymbiotic origin of mitochondria had been considered since the time of Mereschkowsky Martin and Kowallik , the advances in biochemical techniques in the s led to a revival of the idea, and a new and enthusiastic following for it. The driving force behind this renewed. Margulis published a reformulation of the endosymbiotic theory in , and endosymbiosis has subsequently become the accepted view of the origin of mitochondria.

There is still disagreement about how this endosymbiosis arose, and which organisms it involved, but there is a general agreement now that the mitochondrion has descended ultimately from a free-living bacterium. In the course of a little over years, scientists have gone from the first observations of mitochondria to an understanding of their structure, function, inheritance, and origin. The mitochondrial genomes of over different species are now known Tsang and Lemire , as are the effects of mutations in many mitochondrial genes. There are, however, basic questions still left to be answered.

Which organisms contributed to the first eukaryotic cell? Why do mitochondria retain a genome? Can mitochondria still function without their own genomes? Why are only certain mitochondria passed on to the next generation? All developments seem to be from simple to more complex forms. Whether this is true or just an imaginary chain of events that fits more comfortably with our way of thinking remains to be seen. The anthropocentric view comes naturally to us. Nonetheless, the evolution of life is often thought to have occurred in a smooth and gradual manner.

The first group of organisms on our planet, the prokaryotes, are generally the simplest. In contrast, take eukaryotes, with ourselves as the glorifying example of how complex life can be.

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The gradual transformation of a prokaryote into a primitive anucleate eukaryote is still considered the logical chain of events in many textbooks. Accordingly, this primitive eukaryote at one stage took up a free-living bacterium which converted into our modern-day mitochondrion. Such endosymbiosis theories for the evolution of eukaryotes at one stage involved amitochondriate i.

This hypothetical group received recognition in the now defunct kingdom of the Archezoa Cavalier-Smith All studied members of this group have been shown to contain mitochondria of some sort van der Giezen et al. This raises. Normally, one would expect intermediary stages of evolutionary development to be capable of producing a lineage of descendants even if the ancestors themselves become extinct. So, why do we not see truly amitochondriate eukaryotes nowadays? The latter scenario suggests that, although these organisms did evolve in a particular environmental niche, they no longer occupy this niche, either because it does not exist anymore or, again, because its former occupants lost out to more competitive eukaryotes.

An easier way to explain the absence of intermediate forms is to suggest they never existed in the first place. Although this might run in the face of our convenient way of ordering things in a gradual progression from simple to more complex, it actually explains our observations without invoking subsequent events selective culling of the amitochondriates. Let us consider a counterintuitive but satisfying proposal for this event, and one that explains several key aspects in the evolution of eukaryotes.

Firstly, the origin of eukaryotes and mitochondria was the same event. In addition, in contrast to general belief, the eubacterial organism that gave rise to the mitochondrion was not an obligate aerobe, far from it. Finally, again in contrast to general belief, the reason for the establishment of the mitochondrion was not energy production. The name of this heretical hypothesis? The hydrogen hypothesis Martin and Muller , which suggests that hydrogen, and not oxygen or energy, was the currency for the establishment of the mitochondrial endosymbiont.

This suggests that the host was able to metabolise hydrogen. Eukaryotic genome analyses have indicated that almost all informational genes i. In contrast, all operational genes, i. One reason is the similarity of its aerobic respiration to mitochondrial respiration.

Meaning of "guaré" in the Portuguese dictionary

But here is a problem: methanogens are one of the most oxygen-intolerant prokaryotes, and cannot produce any energy in the presence of oxygen. So, in a last-ditch attempt, the mitochondrial endosymbiont is put forward as a saviour of the oxygen-sensitive host Kurland and Andersson But why put an oxygen scavenger inside the host it is supposedly protecting from harm? One would not put the knights on the courtyard but put them up on the walls to fend off any enemy. The events leading to the establishment of the mitochondrial endosymbiont. Middle: A more intimate relationship results into a larger surface area that can be used for interspecies hydrogen transfer.

Top right: After eventually becoming fully incorporated, the proteobacterium initially kept producing hydrogen and in return received reduced organic compounds. Martin and Muller The hydrogen hypothesis does present the symbiosis as an interspecies hydrogen transfer gone too far.

Subsequent gene transfers forged the symbiosis for eternity. It has been argued that anaerobic metabolism could not have been the driving force in times when atmospheric oxygen concentrations were rising Kurland and Andersson The concentration of atmospheric oxygen around the time of the endosymbiosis about 2, million years ago; Martin et al. Perhaps more importantly, large parts of ocean waters around these times were anoxic Canfield , and it is thought that these important evolutionary events would have taken place in the sea and not on the land as perhaps commonly thought. So, oxygen seems to have been an extremely unlikely factor to have influenced the establishment of the mitochondrial endosymbiont and hydrogen seems more important then ever imagined.

One problem discussing mitochondrial function is that there does not seem to be a typical mitochondrion. Mitochondria evolved over a period of 2, million years in an huge variety of organisms living under an enormous range of environmental conditions van der Giezen and Tovar Mitochondria range from archetypal aerobic mitochondria, via various anaerobic versions and hydrogenosomes, to the most derived forms, mitosomes Tielens et al.

Nonetheless, currently we know of at least one function found in all mitochondrial varieties; iron—sulphur cluster assembly Lill and Muhlenhoff This essential pathway produces iron—sulphur co-factors for both mitochondrial and cytosolic enzymes involved in electron transport, enzyme catalysis, and regulation of gene expression. The most aerobic of mitochondria are involved in oxidative phosphorylation using oxygen as terminal electron acceptor, while more anaerobic versions use alternative electron acceptors such as nitrate Tielens et al.

Hydrogenosomes, similarly to aerobic mitochondria, convert pyruvate to acetylcoenzyme A, however not using pyruvate dehydrogenase but by means of the oxygensensitive pyruvate:ferredoxin oxidoreductase Embley et al. All these mitochondrial variants produce energy, be it by means of harvesting the electrochemical gradient generated via the respiratory chain or by substrate-level phosphorylation. Mitosomes on the other hand are not known to be directly involved in energy generation; currently, their function seems exclusively tied to iron—sulfur cluster assembly van der Giezen et al.

As discussed by van der Giezen and Tovar , mitochondria are an enormously diverse set of various organelles. Even if one is not willing to include the anaerobic varieties as being mitochondrial, the vast biochemical repertoire present in aerobic mitochondria alone is staggering. In addition to this biochemical heterogeneity, there exists a genetic heterogeneity as well. There does not exist such a thing as a mitochondrial genome. This genome can be as small as 5, bases in the case of Plasmodium falciparum Feagin et al.

Synonyms and antonyms of guaré in the Portuguese dictionary of synonyms

Strangely enough, although the rice mitochondrial genome is 80 times larger than the Plasmodium one, it does not code for 80 times as many genes. Although plant mitochondrial genomes tend to be the largest, the mitochondrial genome which actually contains the most genes is the one from the freshwater protozoon Reclinomonas americana, which contains 97 genes Lang et al. The median is therefore something around 45 genes.

These genes have either been lost owing to redundancy the host already contained homologous genes or been transferred to the host genome Timmis et al. The remaining mitochondrial genes are involved in a limited set of functions; always respiration and translation as evident in the case of P.

The partially sequenced hydrogenosomal genome from the ciliate Nyctotherus ovalis does indeed code for parts of a mitochondrial electron transport chain Boxma et al. Other hydrogenosomes and. Elements of energy transduction in respiration and oxidative phosphorylation in mitochondria. The mitochondrial inner membrane is shown in yellow. Vectorial electron transfer is depicted as thin, dark-blue arrows. Other chemical conversions are given black arrows.

The major, variable environmental input is oxygen O2 , shown in blue. Subunits of protein complexes are coloured according to the location of the genes encoding them. Mitochondria are usually pink or reddish-brown, the colour of cytochromes and iron—sulphur proteins, so reddish-brown subunits have genes in the mitochondrion and are synthesised in the mitochondrial matrix; light-brown subunits have genes in the nucleus, and are imported from the cytosol as precursors. Adapted from Allen a. Reactive oxygen species, generated largely by the mitochondrial electron transport chain, damage the mitochondrial proteins and DNA, and the mitochondrial theory of ageing, simply put, states that this damage leads to ageing and its associated degenerative diseases Fig.

This theory was first put forward by Harman , although earlier observations had linked life span to metabolic rate: the higher the metabolic rate, the shorter the life span Pearl Why we grow old and die: the mitochondrial theory of ageing. Free radicals whose reactions are symbolised by a star , including the superoxide anion radical, O2. Free-radical mutagenesis of mitochondrial DNA mtDNA then impairs the structure and function of respiratory chain proteins, in turn increasing the frequency of free-radical production. Univalent reduction of oxygen by semiquinone anion radicals may be an important initial step, since ubisemiquinone is an intermediate in protonmotive Q-cycles in oxidative phosphorylation, and readily reduces oxygen to the superoxide anion radical, O2.

Other oxygen free radicals and sites in the respiratory chain may also be involved. Direct damage to proteins and membranes may accelerate the cycle and initiate somatic degeneration. Mitochondria may minimise, but never eliminate, mutagenic electron transfers.

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Adapted from Allen When Harman first put forward his hypothesis, it had not actually been shown that cells generated free radicals, and it was only in , with the discovery of superoxide dismutase McCord and Fridovich , that this question was satisfactorily answered. It is now known that cells generate reactive oxygen species at many sites, the majority of these being within the mitochondria.

The two major sites are believed to be sites I and III of the respiratory chain. Experiments increasing the redox potential of either site I or site III increase the rate of generation of free radicals Chen et al. Both of these complexes reduce ubiquinone ubiquinol is also oxidised by complex III , and univalent reduction of oxygen probably occurs by electron transfer from the ubisemiquinone free radical, an intermediate in ubiquinone—ubiquinol oxidation and reduction.

It is not known how much of the oxygen consumption of the cell is turned over to generating reactive oxygen species, but the figure is thought to be between 2 Chance et al. The cell has very efficient scavenging mechanisms, and so these figures may be underestimates.

How much damage mitochondrial DNA suffers as a result of reactive oxygen species generation is still an open question. Studies have shown Shigenaga et al. The field of ageing research — what causes ageing and how do we stop, slow, or even reverse it — is an active one. Almost everyone would like to be able to extend their life span. Long-lived mutants of the nematode worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, and even mice have been established in the laboratory, as reviewed by Balaban et al. These animals also seem to have a reduced reproductive capacity.

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It seems that reducing generation of reactive oxygen species does indeed slow ageing, but at what cost? These animals can survive under laboratory conditions, but it is unlikely that they could survive in nature. Perhaps our mortality is the price we have to pay for survival in the short term, and our immortality has been secured by reproduction.

Mitochondrial DNA is kept in the most hostile environment in the cell. While the vast majority of genes from the original endosymbiont have been transferred to the nucleus or lost, a small core of genes persist in the mitochondrial matrix. There is strong evidence that damage to mitochondrial DNA by reactive oxygen species generated during oxidative phosphorylation contributes to ageing and death of an organism, and so it is reasonable to assume that there must be a very compelling reason for the organism to continue to keep DNA there.

Mitochondria have descended, in evolution, from free-living bacteria Gray and Doolittle ; Gray ; Martin et al. Before the bacterial origin of mitochondria was generally appreciated, there were attempts to account for mitochondrial biogenesis in terms of sequestration of nuclear DNA in the cytoplasm. These need not detain us. However, there is a more recent dogma: that mitochondria retain genes and genetic systems because they are descended from bacteria.

This statement, while correct, is not a complete explanation. For one thing, there are clearly subcellular organelles, hydrogenosomes and mitosomes, which are also derived from bacteria, and which no longer possess their own, internal genetic systems van der Giezen et al.

Another objection to this otherwise reasonable first guess — mitochondria happen to be stuck with bacterial genes — is as follows: many mitochondrial proteins with homology to bacterial proteins are now encoded in the cell nucleus, and are successfully imported, post-translationally, as precursors, prior to processing and assembly into functional complexes Schatz Indeed, the major respiratory chain complexes are hybrids as regards the location of the genes for their subunits Fig.

Thus, even granted the endosymbiotic origin of mitochondria, the persistence of mitochondrial genes and genomes requires explanation: if most ancestral, bacterial genes have been successfully relocated to the cell nucleus, then why not all? What is it about mitochondrial genes, or their gene products, that has prevented their successful removal to the nucleus?

Why do mitochondria and chloroplasts require their own separate genetic systems when other organelles that share the same cytoplasm, such as peroxisomes and lysosomes, do not? We cannot think of compelling reasons why the proteins made in mitochondria and chloroplasts should be made there rather than in the cytosol.

There seems to be no explicit proposal for the most widely held hypothesis for the persistence of mitochondria genomes, but the hypothesis is implicit in many discussions of mitochondrial structure and function. For example, and in contrast to the open question posed by Alberts et al. Mitochondrial DNA is a relic of ancient history. It is a legacy from a single aerobic bacterium that took up residence in the cytoplasm of a primitive cell. Most of the genes of this ancient symbiont were either lost or transferred over the course of evolution to the nucleus of the host cell, leaving only a handful of genes to encode some of the most hydrophobic proteins of the inner mitochondrial membrane.

This view amounts to mitochondrial genes being stuck where they are because of an insuperable difficulty if translocating hydrophobic proteins between subcelluar compartments. Yet there seems to be no evidence that hydrophobicity presents a particular barrier to protein import. This hypothesis states that mitochondria and chloroplasts contain genes whose expression must be under the direct, regulatory control of the redox state of their gene products, or of electron carriers with which their gene products interact Fig.

These genes comprise a primary subset of organellar genes. The requirement for redox control of these genes then confers a selective advantage upon location of that gene within the organelle instead of in the cell nucleus. Mitochondrial and chloroplast genomes also contain genes for components of the their own, distinct, genetic systems. These genes comprise a secondary subset of organellar genes: genetic system genes. Retention of genetic system genes is necessary for the operation of redox control of expression of genes in the primary subset: bioenergetic genes.

Without genes in the primary subset, the function of genetic system genes is eventually lost, and organelles lose their genomes. This hypothesis of co-location for redox regulation of gene expression, CORR, was first outlined, in general terms, in a review on protein phosphorylation in regulation of photosynthesis Allen The hypothesis was put forward in two articles Allen a, b , where the function of the location of organellar genes was proposed as redox regulation of gene expression.

CORR applies equally to mitochondria and chloroplasts, and accounts for the fact that both of these organelles possess membrane-intrinsic electron transport systems along with discrete, extranuclear genetic systems. CORR rests on ten assumptions, or principles, as follows:. Gene expression and principal pathways of biosynthesis of subunits of protein complexes involved in respiration and oxidative phosphorylation in animal mitochondria. Reddishbrown DNA, RNA, and protein subunits are located and synthesised in the mitochondrial matrix; light-brown protein subunits have genes also light brown in the nucleus, and are imported from the cytosol as precursors.

White genes and ribosomal and protein subunits are nuclear-cytoplasmic and of archaebacterial origin. Reddish-brown and light-brown genes and ribosomal and protein subunits are of bacterial origin. The major, variable environmental input is oxygen blue. It is proposed that it is beyond the ability of the nuclear-cytoplasmic system to respond rapidly and directly to changes in oxygen concentration or partial pressure, and so redox regulation of gene expression red arrows has been retained from the ancestral, bacterial endosymbiont.

This redox regulation requires co-location of certain genes, with their gene products, within the mitochondrion. Endosymbiotic origin. As now generally agreed, mitochondria and chloroplasts evolved from free-living bacteria. Unselective gene transfer. Gene transfer between the symbiont or organelle may occur in either direction and is not selective for particular genes. Unselective protein import. There is no barrier to the successful import of any precursor protein, nor to its processing and assembly into a functional, mature form.

Evolutionary continuity of redox control.

Direct redox control of expression of certain genes was present in the bacterial progenitors of mitochondria and chloroplasts, and was vital for selectively advantageous cell function before, during, and after the transition from bacterium to organelle. The mechanisms of this control have been conserved. Selective value of redox control. For each gene under redox control principle 4 , it is selectively advantageous for that gene to be retained and expressed only within the organelle.

Selective value of nuclear location for genes not under redox control. For each bacterial gene that survives and is not under redox control, it is selectively advantageous for that gene to be located in the nucleus and expressed only in the nucleus and cytosol. If the mature gene product functions in chloroplasts or mitochondria, the gene is first expressed in the form of a precursor for import.

Continued and contemporary operation of natural selection for gene location. For any species, the distribution of genes between organelle by principle 5 and nucleus by principle 6 is the result of selective forces which continue to operate. Gerente Executiva Aline Tobal aline gpadrao.


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