Why do protons accumulate outside the membrane

Are you sure? Yes No. Institut Pasteur, Paris, France. Additional information Copyright owner: Springer Netherlands, Data set: Springer. Publisher Springer Netherlands. You have to log in to notify your friend by e-mail Login or register account. Download to disc. High contrast On Off. Close window. Assign to yourself. Assign to other user Search user Invite. Assign Wrong email address. But the dependence of life on proton gradients might also have prevented the evolution of life beyond the prokaryotic level of complexity, until the unique chimeric origin of the eukaryotic cell overcame this obstacle.

Allen, J. The function of genomes in bioenergetic organelles. Efremov, R. Nature , — doi Lane, N. How did LUCA make a living? Chemiosmosis in the origin of life. Bioessays 32 , — doi The energetics of genome complexity. Nature , Martin, W. On the origin of biochemistry at an alkaline hydrothermal vent.

Mitchell, P. Coupling of phosphorylation to electron and hydrogen transfer by a chemi-osmotic type of mechanism. What Is a Cell? Eukaryotic Cells. Cell Energy and Cell Functions. Photosynthetic Cells. Cell Metabolism. The Origin of Mitochondria. Mitochondrial Fusion and Division. The Origin of Plastids. The Origins of Viruses. Discovery of the Giant Mimivirus. Volvox, Chlamydomonas, and the Evolution of Multicellularity. Yeast Fermentation and the Making of Beer and Wine. Dynamic Adaptation of Nutrient Utilization in Humans.

Nutrient Utilization in Humans: Metabolism Pathways. An Evolutionary Perspective on Amino Acids. Mitochondria and the Immune Response. Stem Cells in Plants and Animals. Promising Biofuel Resources: Lignocellulose and Algae. The Discovery of Lysosomes and Autophagy. The Mystery of Vitamin C. By: Nick Lane, Ph. Citation: Lane, N. Nature Education 3 9 The proton gradients that power respiration are as universal as the genetic code itself, giving an insight into the origin of life and the singular origin of complexity.

Aa Aa Aa. How Cells Breathe. Fine Details. Figure 2: The structure of complex I, the largest protein complex involved in respiration in bacteria and mitochondria, as revealed by X-ray crystallography. The structure a suggests the piston mechanism shown b , whereby shunting the piston drives protons across the membrane through three separate channels. Figure Detail. Proton Motivation. Proton Gradients at the Origin of Life. Figure 3. Why Proton Gradients Are Necessary.

Figure 4: Why chemistry is not enough. Figure 5: Why chemiosmosis solves the problem. If a reaction doesn't release enough energy to generate 1 ATP, it can be repeated endlessly until it has pumped enough protons to generate 1 ATP.

The Origin of Complex Life. Figure 6. References and Recommended Reading Allen, J. Nature , Martin, W. Nature , 17 doi First life. American Scientist 94 , 32—39 Silverstein, T. The mitochondrial phosphate-to-oxygen ratio is not an integer. Biochemistry and Molecular Biology Education 33 , — Article History Close. Share Cancel. Revoke Cancel. Keywords Keywords for this Article. Save Cancel. Flag Inappropriate The Content is: Objectionable. Flag Content Cancel. Email your Friend.

Submit Cancel. This content is currently under construction. For a protein or chemical to accept electrons, it must have a more positive redox potential than the electron donor. Therefore, electrons move from electron carriers with more negative redox potential to those with more positive redox potential.

The four major classes of electron carriers involved in both eukaryotic and prokaryotic electron transport systems are the cytochromes , flavoproteins , iron-sulfur proteins , and the quinones. In aerobic respiration , the final electron acceptor i.

This electron carrier, cytochrome oxidase , differs between bacterial types and can be used to differentiate closely related bacteria for diagnoses.

For example, the gram-negative opportunist Pseudomonas aeruginosa and the gram-negative cholera-causing Vibrio cholerae use cytochrome c oxidase, which can be detected by the oxidase test, whereas other gram-negative Enterobacteriaceae, like E. There are many circumstances under which aerobic respiration is not possible, including any one or more of the following:.

One possible alternative to aerobic respiration is anaerobic respiration , using an inorganic molecule other than oxygen as a final electron acceptor. There are many types of anaerobic respiration found in bacteria and archaea. Many aerobically respiring bacteria, including E. However, anaerobic respirers use altered ETS carriers encoded by their genomes, including distinct complexes for electron transfer to their final electron acceptors.

Smaller electrochemical gradients are generated from these electron transfer systems, so less ATP is formed through anaerobic respiration.

Beyond the use of the PMF to make ATP, as discussed in this chapter, the PMF can also be used to drive other energetically unfavorable processes, including nutrient transport and flagella rotation for motility. Figure 1. This flow of hydrogen ions across the membrane, called chemiosmosis , must occur through a channel in the membrane via a membrane-bound enzyme complex called ATP synthase Figure 1.

The tendency for movement in this way is much like water accumulated on one side of a dam, moving through the dam when opened.

The turning of the parts of this molecular machine regenerates ATP from ADP and inorganic phosphate P i by oxidative phosphorylation , a second mechanism for making ATP that harvests the potential energy stored within an electrochemical gradient.

The number of ATP molecules generated from the catabolism of glucose varies. For example, the number of hydrogen ions that the electron transport system complexes can pump through the membrane varies between different species of organisms. In aerobic respiration in mitochondria, the passage of electrons from one molecule of NADH generates enough proton motive force to make three ATP molecules by oxidative phosphorylation, whereas the passage of electrons from one molecule of FADH 2 generates enough proton motive force to make only two ATP molecules.

Thus, the 10 NADH molecules made per glucose during glycolysis, the transition reaction, and the Krebs cycle carry enough energy to make 30 ATP molecules, whereas the two FADH 2 molecules made per glucose during these processes provide enough energy to make four ATP molecules.