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PHOTOSYNTHESIS HAS TWO MAIN REACTIONS

Light energy is trapped in the chloroplast lamellae by photosynthetic pigments which are either chlorophylls e.g.

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how is atp synthesised in photosynthesis

In the section of ATP synthesis, you mentioned how enzymes in the citric acid cycle can undergo substrate-level phosphorylation to produce small amounts of ATP, but the wikipedia article for citric acid cycle explains how the NADH generated by the citric acid cycle is fed into oxidative phosphorylation pathway in order to produce ATP. Does this mean that the citric acid cycle generates ATP by both substrate-level phosphorylation and oxidative phosphorylation?

 The light used in photosynthesis is absorbed by a green pigment called chlorophyll.

The earliest cells, prokaryotes living in an early Earth devoid of free oxygen, used various alternative electron acceptors to carry on anaerobic cellular respiration. After cyanobacteria invented oxygenic photosynthesis and pumped oxygen gas into the oceans and atmosphere, bacteria that adapted their electron transport chains to exploit oxygen as the terminal electron acceptor gained higher energy yield and thus a competitive advantage. One line of aerobic bacteria took up an endosymbiotic relationship within a larger host cell, providing ATP in exchange for organic molecules. The endosymbiont was the evolutionary ancestor of mitochondria. This endosymbiosis must have occurred in the ancestor of all eukaryotes, because all existing eukaryotes have mitochondria (Martin and Mentel, 2010). The evidence for the endosymbiont origin of mitochondria can be found in:

How is ATP used in photosynthesis? - Quora

Photosynthesis is the essential process which plants undergo in order to survive.

We have seen how ATP synthase acts like a proton-powered turbine, and uses the energy released from the down-gradient flow of protons to synthesize ATP. The process of pumping protons across the membrane to generate the proton gradient is called . Chemiosmosis is driven by the flow of electrons down the electron transport chain, a series of protein complexes in the membrane that forms an electron bucket brigade. Each of these protein complexes accepts and passes on electrons down the chain, and pumps a proton across the membrane for each electron it passes on. Ultimately, the last complex in the electron transport chain passes the electrons to molecular oxygen (O2) to make water, in the case of aerobic respiration.

(The process of photosynthesis is explained
in more detail in my prediction)

Although light intensity seems to be the major factor affecting the
size of ivy leaves, there may have been some influence from other
abiotic factors that have also been measured and taken into account in
this experiment.

The energy needed for photosynthesis is obtained from sunlight

Where light intensity is higher, and photosynthesis can take place easily.

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).

So the photosynthesizing leaf loses substantial amount of water by evaporation.
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  • In the dark no ATP production in photosynthesis ..

    Ø Phosphate – the element is involved in photosynthesis, and needed in the light independent stage to be more precise.

  • How is ATP synthesized in photosynthesis?

    Ø Potassium – this element is needed by enzymes which are involved in photosynthesis and respiration.

  • Respiration & Photosynthesis - Revision Cards in A …

    1 In photosynthesis, ..

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Photosynthesis and ATP Flashcards | Quizlet

If this happens a carrier molecule will pick
up the excited electron, and this can result in the synthesis of ATP
by one of two processes - cyclic or non-cyclic photophosphorolation.

how is ATP synthesised during oxidative phosphorlyation



Non-cyclic photophosphorylation

The excited electron may instead be used to provide the reducing power
needed in the second, light-independent stage of the photosynthetic
process.

Photosynthetic Electron Transport and ATP Synthesis

Of course plant cells contain
mitochondria that can respire fuels like glucose, in a chemoheterotrophic manner, but the glucose was first manufactured by
the plant photoautotrophically in photosynthesise, so light remains the primary energy source.

Cyclic photosynthesis in green plants, animation

The conclusion from the example above is:
The energy provided by ATP hydrolysis is not fixed (as well as theenergy necessary to synthesize ATP). Infirst approximation it depends on the concentrations of ADP, ATP, Piand on the pH. This energy increases logarithmically upon decrease inADP and Pi concentration and upon increase in ATP or H+ concentration (= decreases linearly with increase in pH). The graphs below illustrate this point, showingchange in the upon the change in theconcentrationof one reactant ( axis),assuming that the concentrations of other reactants are kept constantat values used in the example above (red dots indicate the calculated in this example).



To close up this section, I would like to note that although thethermodynamics of the ATP synthesis described here might seem rathercomplex, it is actually much more complex. One point neglected here wasthe different ADP and ATP protonation states (), the other is that the actual substrates in the reactioncatalyzed by ATP synthase are not pure nucleotides, but their magnesiumcomplexes. However, as the magnesium concentration in the living cellis relatively high and the pH is usually above 7.2, so the descriptiongiven is still applicable for thermodynamic estimates.

chemical energy during photosynthesis

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.

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