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Why don't protons diffuse out of the mitochondria during chemiosmosis?

Why don't protons diffuse out of the mitochondria during chemiosmosis?


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If the outer membrane of the mitochondria is very permeable, how do mitochondria maintain a proton gradient by pumping protons into the intermembrane space? Wouldn't they just diffuse into the cytosol?


Diffusion, is by definition (Ficks Law) describing movement along or against some gradient (here its concentration) even if the mechanism of transport differ: active, passive, facilitated. The setup of the electrochemical gradient across membrane, like any thermodynamic process is not perfect, there are always entropy losses. In this case, this manifests as the the diffusion of protons away from the membrane (one source, there are others). Note the connection between entropy of system (Mitochondria) and diffusion (the inefficient process) in this positive feedback process. I think its interesting as someone learning about this stuff to make these connections.

Recalling protons are being delivered freely into the environment (inter membrane space) by Electron Transport Chain. Some protons will diffuse away from membrane surface before they can be pumped back in since these highly charged species cannot passively diffuse back in. The chemiosmosis process, which is sustained by the energy input to drive ATP synthase, depends on maintaining a strong concentration gradient (separation) of H+ on either side of membrane. Since the outer membrane of the mitochondria is porous, it means the protons are free to diffuse out, and will do so because it is entropically favorable. This relationship is best described by $ce{Delta G = RTln(K)}$. Where $ce{K=cfrac{[B]}{[A]}}$ for a process $ce{A ightleftharpoons B}$

Where A= Protons near membrane, B= protons diffused out. Having established that thermodynamically they (protons) will diffuse out[3]. It begs the question will they actually reach the outer membrane in a reasonable time.

Of course over long enough time they will. But over some meaningful scale like 1 second, the proton pump rate of ATP synthase, 100s-1 [5], how far can a proton get ideally?. Back at the envelope calculation (ignoring any resistance effects from solvent, path, etc.) and using some approximate values (for yeast proteins and mitochondria):

From Fick's Rate Law, R, $ sqrt[3]{R} = sqrt[3]{ D A cfrac{[H^+]_c - [H^+]_m}{d}} = 14 mu m $

So in 1 s an average proton ideally can diffuse 14 micrometers from the inner membrane, driven by difference in pH between membrane and cytosol. I think i maybe be fair to presume that based on this the mitochondria is leaking protons into into its near surroundings constantly. (for scale the mitochondria is about 100nm).

Hope that was helpful

VALUES:

Thickness of mitochondria,$d$, equal 0.014 $mu m $ [4]

$ce{[H^+]_m }$ at membrane = $ce{-log[H+] = 10^(-6.8), [H+] = 10^(-6.8)}$ [6]

$ce{[H^+]_c }$ at in cytosol = $ce{[H+] = 10^(-7.40)}$

Diffusion coefficient of H+ in aqueous media $D$ = 7000 $mu m^2$ [2]

A (surface area from which diffusion is taking place) I set to 0.025 $mu m^2$ (guess from average unit cell of crystallized structure of ETC Complex II in yeast).

REFERENCES:

  1. D. Nelson & Cox (2012). Lehninger, Principles of Biochemistry, 6th Ed
  2. https://esc.fnwi.uva.nl/thesis/centraal/files/f1163457446.pdf
  3. http://www.ncbi.nlm.nih.gov/books/NBKhttp://www.atpsynthase.info/FAQ.html
  4. http://www.ncbi.nlm.nih.gov/pubmed/9245766
  5. http://www.atpsynthase.info/FAQ.html
  6. http://jgp.rupress.org/content/139/6/415.full

Award [1] for each structure clearly drawn and correctly labelled.

cell wall &ndash with some thickness

plasma membrane &ndash shown as single line or very thin

cytoplasm pilus/pili &ndash shown as single lines

flagellum/flagella &ndash shown as thicker and longer structures than pili and embedded in cell wall

70S ribosomes nucleoid / naked DNA

approximate width 0.5 &mum / approximate length 2.0 &mum

Award [4 max] if the bacterium drawn does not have the shape of a bacillum (rounded-corner rectangle with length approximately twice its width).

Award [4 max] if any eukaryotic structures included.

Both the passive and active movements must be contrasted to receive a mark. Award [3 max] if no examples are given. Responses do not need to be shown in a table format.

occurs during aerobic respiration

oxidative phosphorylation occurs during the electron transport chain

hydrogen/electrons are passed between carriers

finally join with oxygen (to produce water)

occurs in cristae of mitochondria

chemiosmosis is the movement of protons/hydrogen ions

protons move/are moved against their concentration gradient

into the space between the two membranes

protons flow back to the matrix

through the ATP synthase/synthetase (enzyme)

energy is released which produces more ATP/combines ADP and Pi


How does Chemiosmosis generate ATP?

During chemiosmosis, the free energy from the series of reactions that make up the electron transport chain is used to pump hydrogen ions across the membrane, establishing an electrochemical gradient. The production of ATP using the process of chemiosmosis in mitochondria is called oxidative phosphorylation.

Furthermore, how are 32 ATP produced? Out of the cytoplasm it goes into the Krebs cycle with the acetyl CoA. It then mixes with CO2 and makes 2 ATP, NADH, and FADH. From there the NADH and FADH go into the NADH reductase, which produces the enzyme. From the electron transport chain, the released hydrogen ions make ADP for an end result of 32 ATP.

Also to know, how does Chemiosmosis work?

Chemiosmosis is the method which cells use to create ATP for energy. The electrons move through the electron transport chain to oxygen, where they generate energy which pumps the hydrogen ions against their concentration gradient from matrix to intermemberane space, so they can flow back down again.

What is the process of ATP synthesis?

ATP synthesis involves the transfer of electrons from the intermembrane space, through the inner membrane, back to the matrix. The combination of the two components provides sufficient energy for ATP to be made by the multienzyme Complex V of the mitochondrion, more generally known as ATP synthase.


A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

Ralf Rabus , . Inês A.C. Pereira , in Advances in Microbial Physiology , 2015

4.2.2.4 Ech and Coo

An alternative to Rnf for coupling the oxidation/reduction of ferredoxin with chemiosmosis are the membrane-bound energy-conserving hydrogenases Ech and Coo. These closely related hydrogenases belong to the subgroup of multisubunit membrane-bound energy-conserving [NiFe] hydrogenases, which have subunits related to subunits of complex I, but do not interact with quinones ( Fox, He, Shelver, Roberts, & Ludden, 1996 Hedderich & Forzi, 2005 Vignais & Billoud, 2007 ). They catalyse the reduction of H + with ferredoxin coupled to chemiosmotic energy conservation, or reduction of ferredoxin with H2 driven by reverse electron transport ( Meuer, Kuettner, Zhang, Hedderich, & Metcalf, 2002 ). In SRP, these hydrogenases are mostly present in the Desulfovibrionaceae ( Pereira et al., 2011 Rodrigues, Valente, Pereira, Oliveira, & Rodrigues-Pousada, 2003 ). In D. vulgaris, the Coo hydrogenase is not regulated by CO ( Rajeev et al., 2012 ), as reported for the enzyme from Rhodospirillum rubrum ( Fox et al., 1996 ), and shows considerable expression during growth with lactate/sulphate, in contrast to Ech ( Keller & Wall, 2011 ). During growth with hydrogen/sulphate, the expression of the ech genes is upregulated, while that of the coo genes is downregulated (relative to lactate/sulphate conditions) ( Pereira, He, Valente, et al., 2008 ). The Coo hydrogenase was shown to be essential for syntrophic growth of D. vulgaris with a methanogen in the presence of lactate, but not for growth with lactate/sulphate ( Walker, Stolyar, et al., 2009 ). In D. gigas, which only contains the Ech and the HynAB periplasmic NiFe hydrogenases, a ΔechBC strain was not affected in growth with lactate, H2 or pyruvate with sulphate or by fermentation ( Morais-Silva, Santos, Rodrigues, Pereira, & Rodrigues-Pousada, 2013 ).


Integral Biomathics 2017: The Necessary Conjunction of Western and Eastern Thought Traditions for Exploring the Nature of Mind and Life

John S. Torday , William B. Miller Jr. , in Progress in Biophysics and Molecular Biology , 2017

Abstract

Boundary conditions enable cellular life through negentropy, chemiosmosis , and homeostasis as identifiable First Principles of Physiology. Self-referential awareness of status arises from this organized state to sustain homeostatic imperatives. Preferred homeostatic status is dependent upon the appraisal of information and its communication. However, among living entities, sources of information and their dissemination are always imprecise. Consequently, living systems exist within an innate state of ambiguity. It is presented that cellular life and evolutionary development are a self-organizing cellular response to uncertainty in iterative conformity with its basal initiating parameters. Viewing the life circumstance in this manner permits a reasoned unification between Western rational reductionism and Eastern holism.


What is the use of proton motive force?

It is the force with which protons move in acid-base reactions. It is the force that results in the creation (synthesis) of a high-energy molecule. It is a form of energy that arises due to differences in pH across biological membranes.

Additionally, what is the proton motive force quizlet? Proton-motive force. The energy-rich, unequal distribution of protons established across the membrane. Two components of proton-motive force. 1. chemical gradient- a concentration gradient of protons establishes pH differences across membrane.

Also to know is, what are the two components of the proton motive force?

The protonmotive force across the inner mitochondrial membrane (&Deltap) has two components: membrane potential (&Delta&Psi) and the gradient of proton concentration (&DeltapH).

How are Chemiosmosis and proton motive force different?

As defined, chemiosmosis is the process of diffusion of ions (usually H + ions, also known as protons) across a selectively permeable membrane. This concentration gradient Is formed by the migration of ions which can be used for mechanical work, this phenomenon is called proton motive force.


Abstract

50 years ago Peter Mitchell proposed the chemiosmotic hypothesis for which he was awarded the Nobel Prize for Chemistry in 1978. His comprehensive review on chemiosmotic coupling known as the first “Grey Book”, has been reprinted here with permission, to offer an electronic record and easy access to this important contribution to the biochemical literature. This remarkable account of Peter Mitchell's ideas originally published in 1966 is a landmark and must-read publication for any scientist in the field of bioenergetics. As far as was possible, the wording and format of the original publication have been retained. Some changes were required for consistency with BBA formats though these do not affect scientific meaning. A scanned version of the original publication is also provided as a downloadable file in Supplementary Information. See also Editorial in this issue by Peter R. Rich. Original title: CHEMIOSMOTIC COUPLING IN OXIDATIVE AND PHOTOSYNTHETIC PHOSPHORYLATION, by Peter Mitchell, Glynn Research Laboratories, Bodmin, Cornwall, England.


Glycolysis and Cellular Respiration - Oxidative Phosphorylation

We're back at the arcade and still in the mitochondrion. We just can't get enough. This is our bonus game but also the most important round, because now we will convert our tokens from the citric acid cycle (NADH and FADH2) into tickets (ATP). This is where the bulk of ATP comes from in cellular respiration—not glycolysis nor the citric acid cycle, but oxidative phosphorylation.

If we break it down, it is not too hard to figure out what this long phrase means. "Oxidative" must have something to do with oxidation, which involves a transfer of electrons. "Phosphorylation" is a term we saw earlier, and it means adding phosphate groups. Putting them together, we must be talking about redox reactions and phosphate additions, which isn't all that different from what we dealt with in glycolysis and the citric acid cycle.

The main purpose of oxidative phosphorylation is to transfer electrons from NADH and FADH2 and use them to power ATP production. Similarly, the main point of playing arcade games is to win tickets for prizes (okay, and maybe to have fun and earn high scores to impress our friends).

Oxidative phosphorylation happens in two steps: the electron transport chain and chemiosmosis. Let's take these steps one at a time and break 'em down.

The ABCs of the ETC

We like to call the electron transport chain the ETC. It is sort of like the EAC (East Australian Current) in Finding Nemo, except the ETC transports electrons instead of fish and surfer sea turtles.

All the ETC details we’re about to discuss are specific to cellular respiration and occur in mitochondria. There are other electron transport chains that function in chloroplasts and across the plasma membrane in prokaryotes, and while those are similar, they aren't what any of this is about.

Embedded in the inner membrane of the mitochondria are protein complexes, which are basically blobs of protein. These blobs are numbered I, II, III, and IV (again with the creative naming). Some of the proteins are electron carriers and others are protein pumps. Recall that during the citric acid cycle, NADH and FADH2 were our outputs. These guys are just hanging out in the mitochondrial matrix waiting to load their tiny electrons onto the ETC.

Electrons jumping on the ETC result in NADH being oxidized. These electrons flow from one protein complex to the next in sequential blob order (I, II, III, and then IV). At the end of the ETC, a lonely oxygen atom is waiting patiently to be reduced. Electrons from protein complex IV team up with the oxygen and grab a couple of protons to make water (H2O). Oxygen is the last stop on this wild chain of events, and that's why we call it the terminal electron acceptor.

Protein complexes I and II are electron carriers, but complexes III and IV do double duty. Not only do they ferry electrons down the ETC, but they also function as proton pumps. Blob III uses the electron energy (aka electricity) to pump hydrogen ions (aka protons) through the membrane into the intermembrane space.

FADH2 wants in on the action, too, but NADH pretty much hogs the ETC for itself. That's because we generated a lot more NADH during the Krebs cycle (ten NADH compared to two FADH2). FADH2 has to get on at the second stop, protein complex II, but it follows the same steps afterward. Oxygen is still the terminal electron acceptor, and water is still produced. However, since far fewer FADH2 molecules are hanging out, there are fewer electrons getting on the chain thus, less ATP can be made from FADH2. Sorry, dude.


While electrons ride the ETC, protons are pumped into the intermembrane space.

Chemiosmosis and We're Done

Okay. Some electrons took a ride on the ETC. So what? The protein blobs pumping protons across the membrane have caused a bit of a kerfuffle. We've got a high concentration of protons outside the membrane, and we all know that the cells like to maintain balance. The protons are upset and want back through the membrane. But no dice. Proton pumps are a one-way street. They'll have to go around. Luckily, there's an alley.

There are specialized channels in the membrane that the protons can flow through. These channels are formed by an enzyme called ATP synthase. And what does ATP synthase do? Make ATP, of course. The flow of protons through the ATP synthase channel and across the inner membrane is called chemiosmosis.

The word chemiosmosis is a mash up of "chemical" and "osmosis," and it's just a fancy way of saying ions move across a membrane. When water flows across a membrane, it's called osmosis, and chemiosmosis is a very similar process. In both cases, particles diffuse from an area of high concentration to an area of lower concentration. The gradient of high to low proton concentration has potential energy and can be used to power ATP synthase.

ATP synthase makes ATP by combining ADP and a phosphate group. Think of ATP synthase as a motor driven by protons. The steady stream of protons flowing through the channel provides the power to make ATP. In the same way that flowing water can move a water wheel, protons move the ATP synthase wheel.


ATP synthase makes its own proton channel to get the protons needed for ATP synthesis.

Let's tally the score. From the citric acid cycle, we got ten molecules of NADH and two FADH2. The oxidation of one molecule of NADH during OP resulted in the formation of three ATP. That gives us 30 ATP. FADH2 oxidation resulted in two ATP (four in total). In this round of pinball, we won 34 tickets. Wow! High score! This means the process of oxidative phosphorylation produces 34 molecules of ATP per glucose molecule.

Thirty-four molecules of ATP…are we certain? Better slow your roll. Many sources will report a range for ATP generated during OP rather than a specific number. This is because the NADH produced during glycolysis is stuck out in the cytoplasm of the cell, while both the Krebs cycle and OP occur in the mitochondria. The mitochondrial membrane is impervious to NADH—that thing is on lockdown.

Sometimes NADH can hitch a ride and find its way into the mitochondria to be oxidized for ATP synthesis, and sometimes it misses the bus. Since each molecule of NADH is capable of producing three ATP molecules, if the two chaps from glycolysis aren't accounted for, then six fewer ATP molecules will be made.

Ideally, 34 ATP is the goal (and the number to remember for the test). However, despite the well-oiled machines these cells are, they aren't perfect.

Brain Snack

Cancer cells grow and cause tumors, in part, by mutating the mitochondria so the cells are resistant to apoptosis, or cell death. If cells don't die when they are meant to, they build up into masses of tissue, causing tumors.

Scientists have found that these mutations to the mitochondria often have an unintended side effect: the cell is unable to perform oxidative phosphorylation and produce those 34 ATP 9 . Without the energy power plant of OP, cancer cells have to rely on glycolysis alone to get their energy. Researchers are starting to focus on the mutations of mitochondria to find new treatments for cancer.


Chemiosmotic Theory

The Royal Swedish Academy of Sciences decided to award the 1978 Nobel Prize in Chemistry to
Dr Peter Mitchell, Glynn Research Laboratories, Bodmin, Cornwall, UK, for his contribution to the understanding of biological energy transfer through the formulation of the chemiosmotic theory.

Chemiosmotic Theory of Energy Transfer

Peter Mitchell was born in Mitcham, in the County of Surrey, England, on September 29, 1920. His parents, Christopher Gibbs Mitchell and Kate Beatrice Dorothy (née) Taplin, were very different from each other temperamentally. His mother was a shy and gentle person of very independent thought and action, with strong artistic perceptiveness. Being a rationalist and an atheist, she taught him that he must accept responsibility for his own destiny, and especially for his failings in life.That early influence may well have led him to adopt the religious atheistic personal philosophy to which he has adhered since the age of about fifteen. His father was a much more conventional person than his mother, and was awarded the O.B.E. for his success as a Civil Servant.

Peter Mitchell was educated at Queens College, Taunton, and at Jesus college, Cambridge. At Queens he benefited particularly from the influence of the Headmaster, C. L. Wiseman, who was an excellent mathematics teacher and an accomplished amateur musician. The result of the scholarship examination that he took to enter Jesus College Cambridge was so dismally bad that he was only admitted to the University at all on the strength of a personal letter written by C. L. Wiseman. He entered Jesus College just after the commencement of war with Germany in 1939. In Part I of the Natural Sciences Tripos he studied physics, chemistry, physiology, mathematics and biochemistry, and obtained a Class III result. In part II, he studied biochemistry, and obtained a II-I result for his Honours Degree.

He accepted a research post in the Department of Biochemistry, Cambridge, in 1942 at the invitation of J. F. Danielli. He was very fortunate to be Danielli’s only Ph.D. student at that time, and greatly enjoyed and benefited from Danielli’s friendly and unauthoritarian style of research supervision. Danielli introduced him to David Keilin, whom he came to love and respect more than any other scientist of his acquaintance.

He received the degree of Ph.D. in early 1951 for work on the mode of action of penicillin, and held the post of Demonstrator at the Department of Biochemistry, Cambridge, from 1950 to 1955. In 1955 he was invited by Professor Michael Swann to set up and direct a biochemical research unit, called the Chemical Biology Unit, in the Department of Zoology, Edinburgh University, where he was appointed to a Senior Lectureship in 1961, to a Readership in 1962, and where he remained until acute gastric ulcers led to his resignation after a period of leave in 1963.

From 1963 to 1965, he withdrew completely from scientific research, and acted as architect and master of works, directly supervising the restoration of an attractive Regency-fronted Mansion, known as Glynn House, in the beautiful wooded Glynn Valley, near Bodmin, Cornwall – adapting and furnishing a major part of it for use as a research labotatory. In this, he was lucky to receive the enthusiastic support of his fornler research colleague Jennifer Moyle. He and Jennifer Moyle founded a charitable company, known as Glynn Research Ltd., to promote fundamental biological research and finance the work of the Glynn Research Laboratories at Glynn House. The original endowment of about £250,000 was donated about equally by Peter Mitchell and his elder brother Christopher John Mitchell.

In 1965, Peter Mitchell and Jennifer Moyle, with the practical help of one technician, Roy Mitchell (unrelated to Peter Mitchell), and with the administrative help of their company secretary, embarked on the programme of research on chemiosmotic reactions and reaction systems for which the Glynn Research Institute has become known. Since its inception, the Glynn Research Institute has not had sufficient financial resources to employ more than three research workers, including the Research Director, on its permanent staff. He has continued to act as Director of Research at the Glynn Research Institute up to the present time. An acute lack of funds has recently led to the possibility that the Glynn Research Institute may have to close.

Mitchell studied the mitochondrion, the organelle that produces energy for the cell. ATP is made within the mitochondrion by adding a phosphate group to ADP in a process known as oxidative phosphorylation. Mitchell was able to determine how the different enzymes involved in the conversion of ADP to ATP are distributed within the membranes that partition the interior of the mitochondrion. He showed how these enzymes’ arrangement facilitates their use of hydrogen ions as an energy source in the conversion of ADP to ATP.

Peter Mitchell’s 1961 paper introducing the chemiosmotic hypothesis started a revolution which has echoed beyond bioenergetics to all biology, and shaped our understanding of the fundamental mechanisms of biological energy conservation, ion and metabolite transport, bacterial motility, organelle structure and biosynthesis, membrane structure and function, homeostasis, the evolution of the eukaryote cell, and indeed every aspect of life in which these processes play a role. The Nobel Prize for Chemistry in 1978, awarded to Peter Mitchell as the sole recipient, recognized his predominant contribution towards establishing the validity of the chemiosmotic hypothesis, and ipso facto, the long struggle to convince an initially hostile establishment.

NOBEL PRIZE IN CHEMISTRY FOR BIOLOGICAL ENERGY TRANSFER

Mitchell’s research has been carried out within an area of biochemistry often referred to in recent years as ‘bioenergetics’, which is the study of those chemical processes responsible for the energy supply of living cells. Life processes, as all events that involve work, require energy, and it is quite natural that such activities as muscle contraction, nerve conduction, active transport, growth, reproduction, as well as the synthesis of all the substances that are necessary for carrying out and regulating these activities, could not take place without an adequate supply of energy.

It is now well established that the cell is the smallest biological entity capable of handling energy. Common to all living cells is the ability, by means of suitable enzymes, to derive energy from their environment, to convert it into a biologically useful form, and to utilize it for driving various energy requiring processes. Cells of green plants as well as certain bacteria and algae can capture energy by means of chlorophyll directly from sunlight – the ultimate source of energy for all life on Earth – and utilize it, through photosynthesis, to convert carbon dioxide and water into organic compounds. Other cells, including those of all animals and many bacteria, are entirely dependent for their existence on organic compounds which they take up as nutrients from their environment. Through a process called cell respiration, these compounds are oxidized by atmospheric oxygen to carbon dioxide and water.

During both photosynthesis and respiration, energy is conserved in a compound called adenosine triphosphate, abbreviated as ATP. When ATP is split into adenosine diphosphate (ADP) and inorganic phosphate (Pi), a relatively large amount of energy is liberated, which can be utilized, in the presence of specific enzymes, to drive various energy-requiring processes. Thus, ATP may be regarded as the universal ‘energy currency’ of living cells. The processes by which ATP is formed from ADP and Pi during photosynthesis and respiration are usually called ‘photophosphorylation’ and ‘oxidative phosphorylation’, respectively. The two processes have several features in common, both in their enzyme composition – both involve an interaction between oxidizing (electron-transferring) and phosphorylating enzymes – and in their association with cellular membranes. In higher cells, photophosphorylation and oxidative phosphorylation occur in specific membrane-enclosed organelles, chloroplasts and mitochondria, respectively in bacteria, both these processes are associated with the cell membrane.

The above concepts had been broadly outlined by about the beginning of the 1960s, but the exact mechanisms by which electron transfer is coupled to ATP synthesis in oxidative phosphorylation and in photophosphorylation remained unknown. Many hypotheses were formulated, especially with regard to the mechanism of oxidative phosphorylation most of these postulated a direct chemical interaction between oxidizing and phosphorylating enzymes. Despite intensive research in many laboratories, however, no experimental evidence could be obtained for any of these hypotheses. At this stage, in 1961, Mitchell proposed an alternative mechanism for the coupling of electron transfer to ATP synthesis, based on an indirect interaction between oxidizing and phosphorylating enzymes. He suggested that the flow of electrons through the enzymes of the respiratory or photosynthetic electron-transfer chains drives positively charged hydrogen ions, or protons, across the membranes of mitochondria, chloroplasts and bacterial cells. As a result, an electrochemical proton gradient is created across the membrane. The gradient consists of two components: a difference in hydrogen ion concentration, or pH, and a difference in electric potential the two together form what Mitchell calls the ‘protonmotive force’. The synthesis of ATP is driven by a reverse flow of protons down the gradient. Mitchell’s proposal has been called the ‘chemiosmotic theory’.

This theory was first received with scepticism but, over the past 15 years, work in both Mitchell’s and many other laboratories have shown that the basic postulates of his theory are correct. Even though important details of the underlying molecular mechanisms are still unclear, the chemiosmotic theory is now generally accepted as a fundamental principle in bioenergetics. This theory provides a rational basis for future work on the detailed mechanisms of oxidative phosphorylation and photophosphorylation. In addition, this concept of biological power transmission by protonmotive force (or ‘proticity’, as Mitchell has recently began to call it in an analogy with electricity) has already been shown to be applicable to other energy-requiring cellular processes. These include the uptake of nutrients by bacterial cells, cellular and intracellular transport of ions and metabolites, biological heat production, bacterial motion, etc. In addition, the chloroplasts of plants, which harvest the light-energy of the sun, and the mitochondria of animal cells, which are the main converters of energy from respiration, are remarkably like miniaturized solar- and fuel-cell systems. Mitchell’s discoveries are therefore both interesting and potentially valuable, not only for the understanding of biological energy-transfer systems but also in relation to the technology of energy conversion.


What is meant by proton motive force?

The proton motive force occurs when the cell membrane becomes energized due to electron transport reactions by the electron carriers embedded in it. Basically, this causes the cell to act like a tiny battery. Its energy can either be used right away to do work, like power flagella, or be stored for later in ATP.

what is the proton motive force quizlet? Proton-motive force. The energy-rich, unequal distribution of protons established across the membrane. Two components of proton-motive force. 1. chemical gradient- a concentration gradient of protons establishes pH differences across membrane.

Thereof, what is the proton motive force used for?

The proton-motive force created by the pumping out of protons by the respiratory chain complexes is in the mitochondria of most tissues mainly used to translocate protons through the ATP synthase complex, leading to the formation of ATP from adenosine diphosphate (ADP) and phosphate.

What are the two components of the proton motive force?

The protonmotive force across the inner mitochondrial membrane (&Deltap) has two components: membrane potential (&Delta&Psi) and the gradient of proton concentration (&DeltapH).


Watch the video: Τι είναι η Κβαντική Φυσική; (May 2022).