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(The ATP Synthase protein is imbedded in the membrane).

Like water running downhill, this provides energy to drive various processes including ATP synthesis.

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And about 95% of this ATP is made by ATP synthase.

ATP synthesis catalyzed by ATP synthase is powered bythe transmembrane electrochemical proton potential difference, composed of twocomponents: the chemical and theelectrical one. The more protons are on one side of a membrane relativetothe other, the higher is the driving force for a proton to cross themembrane. As proton is a charged particle, its movement is alsoinfluenced by electrical field: transmembrane electrical potentialdifference will drive protons from positively charged side tothe negatively charged one. A water mill is a good analogy: the difference between the water levelsbefore and after the dam provides potential energy; downhill water flowrotates thewheel; the rotation is used to perform some work (ATP synthesis in ourcase). Quantitatively is measured in Joules per mole (J mol-1) and isdefined as:
where the "" and "" indices denote the ositively and the egatively charged sides of thecoupling membrane; is Faraday constant(96 485 C mol-1); is the molar gas constant(8.314 J mol-1K-1), is the temperature in Kelvins, and is thetransmembrane electrical potential difference involts. The value of tells, how much energy is required (or is released, depending on thedirection of the transmembrane proton flow) to move 1 mol of protonsacross the membrane.
It is often more convenient to use not , but protonmotive force ():

At room temperature (25oC) the protonmotive force (inmillivolts, as well as )is:
In the absence of transmembrane pH difference equals the transmembraneelectrical potential difference and can be directly measured by severalexperimental techniques (i.e. permeate ion distribution,potential-sensitive dyes, electrochromic carotenoid bandshift, etc.).Each pH unit of the transmembrane pH gradient corresponds to 59 mVof .
For most biological membranes engaged in ATP synthesis the value lies between 120 and 200mV ( between 11.6 and19.3 kJ mol-1).
The catalytic mechanism of ATP synthasemost probably involves rotation of Gamma subunit together with subunitEpsilon and -subunitoligomer relative to the rest of the enzyme. Such rotation wasexperimentally shown for ATP hydrolysis uncoupled to protontranslocation. Moreover, recent experiments revealed, that if Gammasubunit is mechanically forced into rotation, ATP synthesis takes placeeven without proton-translocating FO-portion.
It seems most probable that such rotation takes place . However, there is nodirect experimental evidence for such rotary mechanism in the intactenzyme under physiological conditions.
The proposed mechanism is the following:
ATP synthase activity is specifically inhibited by several compounds(both organic and inorganic). Most of these inhibitors are very toxic, so great careand appropriate safety precautions are essential when working with them (it is not very surprising thatwe get unhappy when OUR ATP synthase is blocked!).Most inhibitors are specific for either proton-translocating FO-portion, or hydrophilicF1-portion, so the section below is divided accordingly. Oligomycin is the inhibitor that gave the name "FO" to the membrane-embedded portion of ATP synthase. The subscript letter "O" in FO(not zero!) comes from Oligomycin sensitivity of this hydrophobicphosphorylation Factor in mitochondria.
Oligomycin binds on theinterface of subunit and -ring oligomer and blocks the rotary proton translocation in FO. If the enzyme is well-coupled, the activity of F1is also blocked. Because of the latter phenomenon, a subunit of mitochondrial F1-portionthat connects F1 with FO was named Oligomycin-Sensitivity Conferring Protein (OSCP).This subunit is essential for good coupling between F1 and FO and makes the ATPase activity of F1 sensitive to FO inhibitor oligomycin, hence the name.
Oligomycin is specific for mitochondrial ATP synthase and in micromolar concentrationseffectively blocks proton transport through FO. This inhibitor also works in some bacterial enzymes that show highsimilarity to mitochondrial ATP synthase, e.g. enzyme from purple bacterium . But ATP synthase from chloroplasts and from most bacteria (including )has low sensitivity to oligomycin.
It should also be noted that oligomycin in high concentrations also affects the activity of mitochondrial F1. DCCD (abbreviation for Dicyclohexylcarbodiimide; also known as DCC, as N,N'-dicyclohexylcarbodiimide, as Bis(cyclohexyl)carbodiimide, and as 1,3-dicyclohexylcarbodiimide) is a small organic molecule thatcan covalently modify protonated carboxyl groups. When added to ATP synthase at pH above 8, DCCD almost exclusively reacts with the carboxyl group of the conserved acidic amino acid residue of subunit (that is why subunit is sometimes called "DCCD-binding protein"). that has elevated pK and can therefore be protonated at such a high pH. Modification of the carboxyl group in a single -subunit is enough to renderthe whole -ring oligomer inactive. Because DCCD covalently binds to -subunit,this inhibition is irreversible.
The carboxyl group of the conserved amino acid residue in subunit -subunit is present inall ATP synthases known so far. So DCCD is a universal inhibitor that can FO function in bacterial, mitochondrial and chloroplast enzymes. Moreover, V- and A-type proton-transporting ATPasesare also sensitive to DCCD for the same reason. Sodium-transporting ATP synthases are also effectively inhibited by DCCD.
At lower pH (1 and inactivates it. So this compound canbe considered as an inhibitor of both FO and F1. However, inhibition of FOis highly specific, well-defined, and requires much lower DCCD concentration so usually thisinhibitor is used as FO-specific.

F1ATP Synthase – watch the video below and know this!

DCCD (abbreviation for Dicyclohexylcarbodiimide; also known as DCC, as N,N'-dicyclohexylcarbodiimide, as Bis(cyclohexyl)carbodiimide, and as 1,3-dicyclohexylcarbodiimide) is a small organic molecule thatcan covalently modify protonated carboxyl groups. When added to ATP synthase at pH above 8, DCCD almost exclusively reacts with the carboxyl group of the conserved acidic amino acid residue of subunit (that is why subunit is sometimes called "DCCD-binding protein"). that has elevated pK and can therefore be protonated at such a high pH. Modification of the carboxyl group in a single -subunit is enough to renderthe whole -ring oligomer inactive. Because DCCD covalently binds to -subunit,this inhibition is irreversible.
The carboxyl group of the conserved amino acid residue in subunit -subunit is present inall ATP synthases known so far. So DCCD is a universal inhibitor that can FO function in bacterial, mitochondrial and chloroplast enzymes. Moreover, V- and A-type proton-transporting ATPasesare also sensitive to DCCD for the same reason. Sodium-transporting ATP synthases are also effectively inhibited by DCCD.
At lower pH (1 and inactivates it. So this compound canbe considered as an inhibitor of both FO and F1. However, inhibition of FOis highly specific, well-defined, and requires much lower DCCD concentration so usually thisinhibitor is used as FO-specific.

9.1 and 9.2 Photosynthesis and ATP - 12 cards

The energy needed for this process comes from the proton electrochemical potential difference generated by respiration or photosynthesis.

Chloroplast ATP synthase and the enzyme from some photosyntheticbacteriahave 2 different, although similar, -typesubunits in the protontranslocating FO portion, namely and, one copy ofeach.
High homology is found for most of the ATP synthase subunits fromdifferentbacteria and chloroplasts.

Mitochondrial enzyme is much more complex; are described at the moment. Some of these subunits have high homology to bacterial andchloroplast counterparts, especially subunits Alpha, Beta and Gamma inthe F1 portion and subunits and in the FOportion. Many subunits are unique for the mitochondrial enzyme (see for details).However, the catalytic and proton translocating "core" of the enzyme isstill highly homological to that of bacterial and chloroplast ATPsynthase. The overall topology of the enzyme is also quite similar.

The "" and "" indices denote the ositively and the egatively charged sides of thecoupling membrane.
The pH value is important: the pK value for 2-+i- is 7.2, while thecorresponding pK values for phosphate in ADP and ATP are close to 6.9.
This means that in the pH interval of 6.9-7.2 the prevailingreaction will not include trapping of protons:

ATP Synthase (FoF1-complex): Home

The electrons go through a transport chain which amounts to a kind of respiration in the middle of photosynthesis, in other words the energetically favorable transfer from -0.8 V to +0.4 V drives the synthesis of some ATP.

Sulfate (SO4) is reduced to H2S plus several H2O, and the transfer of electrons from high (NADH) to low (Sulfate) provides enough energy to synthesize ATP.

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  • ATP Synthase: The power plant of the cell - YouTube

    H+ ions accumulate in the intermembrane space and then move down their gradient, moving through ATP Synthase.

  • ATP/ Photosynthesis/ Cellular Respiration Flashcards | …

    Traditionally the thermodynamics of ATP synthesis/hydrolysis isdescribed for the hydrolysis reaction:

  • ATP/ Photosynthesis/ Cellular Respiration

    ATP synthesis

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Video: Chemiosmosis in Photosynthesis & Respiration

The half reaction reduction potential for S -> H2S is +0.14 volts, so the potential difference for the reaction H2S+ NAD+ -> NADH + S is only -0.46 volts, making photosynthesis much easier (starting with water we needed -1.14 volts).

atp synthase role in photosynthesis - …

Inside the inner membrane of the mitochondria there is a chain of electron carriers. This chain is called the electron transport chain. Electrons from the oxidative reactions in the earlier stages of cell respiration pass along the chain. NADH donates two electrons to the first carrier in the chain. These two electrons pass along the chain and release energy from one carrier to the next. At three locations along the chain, enough energy is released to produce ATP via ATP synthase. ATP synthase is an enzyme that is also found in the inner mitochondrial membrane. FADH2 also donates electrons but at a later stage than NADH. Also, enough energy is released at only two locations along the chain by electrons from FADH2. The ATP production relies on energy release by oxidation and it is therefore called oxidative phosphorylation.

Photosynthesis VS Cellular Respiration - Prezi

The energy for ATP synthesis comes from organic molecules (such as carbohydrates), or from sunlight, or from inorganic electron donors. We can classify organisms according to their source of energy and organic carbon:

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