However, more conclusive evidence is needed to elucidate if the RSV-mediated inhibition of cellular respiration that we discuss in this review is really the convergent point of both beneficial and toxic properties. Therefore, it is necessary to comprehensively establish the mechanism of respiration inhibition by RSV.
Importantly, the information reviewed here indicates the toxicological potential of RSV supplementation. Therefore, more clinical trials targeted at specific diseases are needed to search for safe concentrations of RSV supplementation. For example, the toxicity exerted by high doses of RSV could help to treat cancer. On the other hand, risk factors of metabolic disorders related with energy overload as in high-fat and high-carbohydrate diets are ameliorated by low doses of RSV supplementation.
This is probably due to activation of catabolic pathways mediated by AMPK. In this regard, subjects that consume high-energy diets accompanied by RSV supplementation could potentially have health benefits.
Nonetheless, evidence about the effects of RSV supplementation under diets different than those with high-energy is still lacking. The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.
National Center for Biotechnology Information , U. Int J Mol Sci. Published online Mar Maurizio Battino, Academic Editor. Author information Article notes Copyright and License information Disclaimer. Received Jan 21; Accepted Mar 8. This article has been cited by other articles in PMC. Keywords: resveratrol, cellular respiration, molecular mechanism, energy homeostasis, antioxidant, mitochondrial dysfunction.
Biological Significance of Resveratrol in Plants In order to establish the molecular mechanism of the well-known beneficial effects of RSV in mammalian systems, it is important to note that the biological significance of RSV in plants is related to an environmental defense mechanism.
Molecular Mechanism of Resveratrol Toxicity Although the RSV synthesis is elicited to counteract fungal infection, the molecular mechanism of the RSV anti-fungal action is still unclear. Open in a separate window. Figure 1.
Figure 2. Figure 3. Resveratrol and Mitochondrial Dysfunction Mitochondria play a crucial role in metabolic cell functions. Conclusions The evidence discussed in this review allows us to propose that RSV inhibits cellular respiration, and this inhibition is the major effector of the molecular and physiological properties of RSV Table 1.
Table 1 Resveratrol targets sorted according to the mechanism proposed in this review. Conflicts of Interest The authors declare no conflict of interest. References 1. Montero C. Trans-resveratrol and grape disease resistance. A dynamical study by high-resolution laser-based techniques.
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Liu Y. Tome-Carneiro J. Consumption of a grape extract supplement containing resveratrol decreases oxidized LDL and APOB in patients undergoing primary prevention of cardiovascular disease: A triple-blind, 6-month follow-up, placebo-controlled, randomized trial. Food Res. It takes two turns of the cycle to process the equivalent of one glucose molecule.
These high-energy carriers will connect with the last portion of aerobic respiration to produce ATP molecules. One ATP or an equivalent is also made in each cycle. Several of the intermediate compounds in the citric acid cycle can be used in synthesizing non-essential amino acids; therefore, the cycle is both anabolic and catabolic. You have just read about two pathways in glucose catabolism—glycolysis and the citric acid cycle—that generate ATP.
Most of the ATP generated during the aerobic catabolism of glucose, however, is not generated directly from these pathways.
Rather, it derives from a process that begins with passing electrons through a series of chemical reactions to a final electron acceptor, oxygen. These reactions take place in specialized protein complexes located in the inner membrane of the mitochondria of eukaryotic organisms and on the inner part of the cell membrane of prokaryotic organisms. The energy of the electrons is harvested and used to generate a electrochemical gradient across the inner mitochondrial membrane.
The potential energy of this gradient is used to generate ATP. The entirety of this process is called oxidative phosphorylation. The electron transport chain Figure 5a is the last component of aerobic respiration and is the only part of metabolism that uses atmospheric oxygen. Oxygen continuously diffuses into plants for this purpose.
In animals, oxygen enters the body through the respiratory system. Electron transport is a series of chemical reactions that resembles a bucket brigade in that electrons are passed rapidly from one component to the next, to the endpoint of the chain where oxygen is the final electron acceptor and water is produced.
There are four complexes composed of proteins, labeled I through IV in Figure 5c, and the aggregation of these four complexes, together with associated mobile, accessory electron carriers, is called the electron transport chain.
The electron transport chain is present in multiple copies in the inner mitochondrial membrane of eukaryotes and in the plasma membrane of prokaryotes. In each transfer of an electron through the electron transport chain, the electron loses energy, but with some transfers, the energy is stored as potential energy by using it to pump hydrogen ions across the inner mitochondrial membrane into the intermembrane space, creating an electrochemical gradient.
Cyanide inhibits cytochrome c oxidase, a component of the electron transport chain. If cyanide poisoning occurs, would you expect the pH of the intermembrane space to increase or decrease? What affect would cyanide have on ATP synthesis? The pH of the intermembrane space would increase, and ATP synthesis would stop.
As they are passed from one complex to another there are a total of four , the electrons lose energy, and some of that energy is used to pump hydrogen ions from the mitochondrial matrix into the intermembrane space. In the fourth protein complex, the electrons are accepted by oxygen, the terminal acceptor. The oxygen with its extra electrons then combines with two hydrogen ions, further enhancing the electrochemical gradient, to form water.
If there were no oxygen present in the mitochondrion, the electrons could not be removed from the system, and the entire electron transport chain would back up and stop. The mitochondria would be unable to generate new ATP in this way, and the cell would ultimately die from lack of energy. This is the reason we must breathe to draw in new oxygen. In the electron transport chain, the free energy from the series of reactions just described is used to pump hydrogen ions across the membrane.
Hydrogen ions diffuse through the inner membrane through an integral membrane protein called ATP synthase Figure 5b. This complex protein acts as a tiny generator, turned by the force of the hydrogen ions diffusing through it, down their electrochemical gradient from the intermembrane space, where there are many mutually repelling hydrogen ions to the matrix, where there are few.
This flow of hydrogen ions across the membrane through ATP synthase is called chemiosmosis. Chemiosmosis Figure 5c is used to generate 90 percent of the ATP made during aerobic glucose catabolism.
The result of the reactions is the production of ATP from the energy of the electrons removed from hydrogen atoms. These atoms were originally part of a glucose molecule. At the end of the electron transport system, the electrons are used to reduce an oxygen molecule to oxygen ions. The extra electrons on the oxygen ions attract hydrogen ions protons from the surrounding medium, and water is formed. The electron transport chain and the production of ATP through chemiosmosis are collectively called oxidative phosphorylation.
The number of ATP molecules generated from the catabolism of glucose varies. For example, the number of hydrogen ions that the electron transport chain complexes can pump through the membrane varies between species. Another source of variance stems from the shuttle of electrons across the mitochondrial membrane.
The NADH generated from glycolysis cannot easily enter mitochondria. Another factor that affects the yield of ATP molecules generated from glucose is that intermediate compounds in these pathways are used for other purposes. Glucose catabolism connects with the pathways that build or break down all other biochemical compounds in cells, and the result is somewhat messier than the ideal situations described thus far. For example, sugars other than glucose are fed into the glycolytic pathway for energy extraction.
Other molecules that would otherwise be used to harvest energy in glycolysis or the citric acid cycle may be removed to form nucleic acids, amino acids, lipids, or other compounds. Overall, in living systems, these pathways of glucose catabolism extract about 34 percent of the energy contained in glucose.
The citric acid cycle is a series of chemical reactions that removes high-energy electrons and uses them in the electron transport chain to generate ATP. One molecule of ATP or an equivalent is produced per each turn of the cycle. The electron transport chain is the portion of aerobic respiration that uses free oxygen as the final electron acceptor for electrons removed from the intermediate compounds in glucose catabolism. The electrons are passed through a series of chemical reactions, with a small amount of free energy used at three points to transport hydrogen ions across the membrane.
This contributes to the gradient used in chemiosmosis. The products of the electron transport chain are water and ATP. A number of intermediate compounds can be diverted into the anabolism of other biochemical molecules, such as nucleic acids, non-essential amino acids, sugars, and lipids.
These same molecules, except nucleic acids, can serve as energy sources for the glucose pathway. We inhale oxygen when we breathe and exhale carbon dioxide.
What is the oxygen used for and where does the carbon dioxide come from? The carbon dioxide we breathe out is formed during the citric acid cycle when the bonds in carbon compounds are broken. Cellular respiration is a process that all living things use to convert glucose into energy. Autotrophs like plants produce glucose during photosynthesis. Heterotrophs like humans ingest other living things to obtain glucose.
While the process can seem complex, this page takes you through the key elements of each part of cellular respiration. Cellular respiration is a collection of three unique metabolic pathways: glycolysis, the citric acid cycle, and the electron transport chain. Glycolysis is an anaerobic process, while the other two pathways are aerobic. In order to move from glycolysis to the citric acid cycle, pyruvate molecules the output of glycolysis must be oxidized in a process called pyruvate oxidation.
Glycolysis is the first pathway in cellular respiration. This pathway is anaerobic and takes place in the cytoplasm of the cell. This pathway breaks down 1 glucose molecule and produces 2 pyruvate molecules. There are two halves of glycolysis, with five steps in each half. This half splits glucose, and uses up 2 ATP. If the concentration of pyruvate kinase is high enough, the second half of glycolysis can proceed. Some cells e.
However, most cells undergo pyruvate oxidation and continue to the other pathways of cellular respiration. In eukaryotes, pyruvate oxidation takes place in the mitochondria. Pyruvate oxidation can only happen if oxygen is available. In this process, the pyruvate created by glycolysis is oxidized. In this oxidation process, a carboxyl group is removed from pyruvate, creating acetyl groups, which compound with coenzyme A CoA to form acetyl CoA.
This process also releases CO 2. The citric acid cycle also known as the Krebs cycle is the second pathway in cellular respiration, and it also takes place in the mitochondria. The rate of the cycle is controlled by ATP concentration. This pathway is a closed loop: the final step produces the compound needed for the first step.
The citric acid cycle is considered an aerobic pathway because the NADH and FADH 2 it produces act as temporary electron storage compounds, transferring their electrons to the next pathway electron transport chain , which uses atmospheric oxygen. Most ATP from glucose is generated in the electron transport chain. It is the only part of cellular respiration that directly consumes oxygen; however, in some prokaryotes, this is an anaerobic pathway.
In eukaryotes, this pathway takes place in the inner mitochondrial membrane. In prokaryotes it occurs in the plasma membrane. The electron transport chain is made up of 4 proteins along the membrane and a proton pump.
A cofactor shuttles electrons between proteins I—III. Answer the question s below to see how well you understand the topics covered in the previous section. This short quiz does not count toward your grade in the class, and you can retake it an unlimited number of times. Use this quiz to check your understanding and decide whether to 1 study the previous section further or 2 move on to the next section.
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