Photosynthesis

Probably not a substantial claim: may not pass S3 (load-bearing).

Oxygenic photosynthesis involves the conversion of water and CO2 into complex organic molecules such as carbohydrates and oxygen.

“Oxygenic photosynthesis involves the conversion of water and CO2 into complex organic molecules such as carbohydrates and oxygen.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The Calvin-Benson cycle uses ATP and NADPH to convert CO2 into carbohydrates, regenerating ADP and NADP+.

“The Calvin–Benson cycle uses ATP and NADPH to convert CO2 into carbohydrates (Figure 3), regenerating ADP and NADP+.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Cyanobacteria evolved from simpler photosynthetic bacteria that use organic or inorganic compounds such as hydrogen sulfide as an electron source rather than water and thus do not produce oxygen.

“Cyanobacteria themselves are thought to have evolved from simpler photosynthetic bacteria that use either organic or inorganic compounds such a hydrogen sulfide as a source of electrons rather than water and thus do not produce oxygen.”

May combine two claims.

Light energy excites an electron within a chlorophyll molecule in PSII or PSI to a higher energy level; the excited chlorophyll then reduces subsequent acceptors in the chain.

“The light energy is used to excite an electron within a chlorophyll molecule residing in PSII or PSI to a higher energy level; this excited chlorophyll is then able to reduce the subsequent acceptors in the chain.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Oxygenic photosynthesis is thought to have evolved only once during Earth's history in the cyanobacteria.

“Oxygenic photosynthesis is thought to have evolved only once during Earth's history in the cyanobacteria.”

May combine two claims.

The special pair of chlorophylls in the reaction centre are redox-active and can return to the ground state by transferring the S1 excited electron to another species, a process known as charge separation that forms an oxidized special pair and a reduced acceptor.

“Unlike the antenna pigments, the special pair of chlorophylls are ‘redox-active’ in the sense that they can return to the ground state (S0) by the transfer of the electron residing in the S1 excited state (Chl*) to another species. This process is known as charge separation and result in formation of an oxidized special pair (Chl+) and a reduced acceptor (A−).”

May combine two claims.

The light reactions occur in the thylakoid membrane, whereas the dark reactions (Calvin-Benson cycle) occur in the stroma.

“The light reactions of photosynthesis involve light-driven electron and proton transfers, which occur in the thylakoid membrane, whereas the dark reactions involve the fixation of CO2 into carbohydrate, via the Calvin–Benson cycle, which occurs in the stroma (Figure 3).”

Probably not a substantial claim: may not pass S3 (load-bearing).

The light reactions involve electron transfer from water to NADP+ to form NADPH, coupled to proton transfers that lead to phosphorylation of ADP into ATP.

“The light reactions involve electron transfer from water to NADP+ to form NADPH and these reactions are coupled to proton transfers that lead to the phosphorylation of adenosine diphosphate (ADP) into ATP.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In photosynthetic systems, chlorophylls and carotenoids are attached to membrane-embedded proteins known as light-harvesting complexes (LHCs).

“In photosynthetic systems, chlorophylls and carotenoids are found attached to membrane-embedded proteins known as light-harvesting complexes (LHCs).”

May combine two claims.

The water-splitting reaction at PSII and plastoquinol oxidation at cytb6f release protons into the lumen, building a proton gradient.

“The water-splitting reaction at PSII and plastoquinol oxidation at cytb6f result in the release of protons into the lumen, resulting in a build-up of protons in this compartment relative to the stroma.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Blue photons (∼450 nm) are more energetic than red photons (∼650 nm).

“The frequency (ν) of the light and so its energy varies with its colour, thus blue photons (∼450 nm) are more energetic than red photons (∼650 nm).”

May combine two claims.

Cyclic electron flow exists in plants and algae; it recycles electrons from ferredoxin to plastoquinone, produces no net NADPH, but can still form ATP.

“An alternative electron transfer pathway exists in plants and algae, known as cyclic electron flow. Cyclic electron flow involves the recycling of electrons from ferredoxin to plastoquinone, with the result that there is no net production of NADPH; however, since protons are still transferred into the lumen by oxidation of plastoquinol by cytb6f, ATP can still be formed.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Photosynthesis in plants is based on two reactions that are carried out by separate parts of the chloroplast.

“The process of photosynthesis in plants is based on two reactions that are carried out by separate parts of the chloroplast.”

Probably not a substantial claim: may not pass S3 (load-bearing).

1 mol of 680 nm photons of red light has an energy of 176 kJ·mol−1.

“Thus 1 mol of 680 nm photons of red light has an energy of 176 kJ·mol−1.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The protons and electrons from the light reactions are transferred through the thylakoid membrane to create ATP and NADPH.

“The protons and electrons are then transferred through the thylakoid membrane to create the energy storage molecules adenosine triphosphate (ATP) and nicotinomide–adenine dinucleotide phosphate (NADPH).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Ferredoxin is used by ferredoxin-NADP+ reductase (FNR) to reduce NADP+ to NADPH.

“Ferredoxin can then be used by the ferredoxin–NADP+ reductase (FNR) enzyme to reduce NADP+ to NADPH.”

May combine two claims.

ATP synthase allows protons to move down their concentration gradient from the lumen to the stroma; this exergonic reaction powers the endergonic synthesis of ATP from ADP and inorganic phosphate.

“The ATP synthase allows the protons to move down their concentration gradient from the lumen (high H+ concentration) to the stroma (low H+ concentration). This exergonic reaction is used to power the endergonic synthesis of ATP from ADP and inorganic phosphate (Pi).”

May combine two claims.

The oxidized chlorophyll is reduced by water in PSII and by plastocyanin in PSI.

“The oxidized chlorophyll is then reduced by water in the case of PSII and plastocyanin in the case of PSI.”

May combine two claims.

The energy gap between S0 and S1 is spanned by a red photon (∼600-700 nm), whereas the S0 to S2 gap requires a blue photon (∼400-500 nm).

“The energy gap between the S0 and S1 states is spanned by the energy provided by a red photon (∼600–700 nm), whereas the energy gap between the S0 and S2 states is larger and therefore requires a more energetic (shorter wavelength, higher frequency) blue photon (∼400–500 nm) to span the energy gap.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Free-living cyanobacteria are responsible for ∼50% of the world's photosynthesis.

“Free-living cyanobacteria still exist today and are responsible for ∼50% of the world's photosynthesis.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

The acceptor in PSII is plastoquinone and in PSI it is ferredoxin.

“The acceptor in PSII is plastoquinone and in PSI it is ferredoxin.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

cytb6f oxidizes plastoquinol to plastoquinone and reduces plastocyanin.

“cytb6f oxidizes plastoquinol to plastoquinone and reduces a small water-soluble electron carrier protein plastocyanin, which resides in the lumen.”

Probably not a substantial claim: may not pass S3 (load-bearing).

All other organisms that perform oxygenic photosynthesis do so via cyanobacterial endosymbionts or chloroplasts.

“All other organisms, such as plants, algae and diatoms, which perform oxygenic photosynthesis actually do so via cyanobacterial endosymbionts or ‘chloroplasts’.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

In PSII the electron donor is water and in PSI it is plastocyanin.

“If the RC is to go on functioning, the electron deficiency on the special pair must be made good, in PSII the electron donor is water and in PSI it is plastocyanin.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Within the green tissue of the leaf (mainly the mesophyll), each cell contains ∼100 chloroplasts.

“Within the green tissue of the leaf (mainly the mesophyll) each cell (∼100 μm in length) contains ∼100 chloroplasts (2–3 μm in length), the tiny organelles where photosynthesis takes place.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The Z-scheme shows electrons move from the water-oxygen couple (+820 mV) via a chain of redox carriers to NADP+/NADPH (−320 mV).

“The Z-scheme, so-called since it resembles the letter ‘Z’ when turned on its side (Figure 5), thus shows how the electrons move from the water–oxygen couple (+820 mV) via a chain of redox carriers to NADP+/NADPH (−320 mV) during photosynthetic electron transfer.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Plastoquinol carries the electrons derived from water to cytochrome b6f.

“Plastoquinol in turn carries the electrons derived from water to another thylakoid-embedded protein complex called cytochrome b6f (cytb6f).”

May combine two claims.

P680* undergoes charge separation forming P680+ with a redox potential of +1200 mV, sufficient to oxidize water.

“P680* undergoes charge separation that results in the formation of an extremely oxidizing species P680+ which has a redox potential of +1200 mV, sufficient to oxidize water.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The variety of pigments present within each type of photosynthetic organism reflects the light environment in which it lives.

“The variety of pigments present within each type of photosynthetic organism reflects the light environment in which it lives; plants on land contain chlorophylls a and b and carotenoids such as β-carotene, lutein, zeaxanthin, violaxanthin, antheraxanthin and neoxanthin (Figure 6).”

Probably not a substantial claim: may not pass S3 (load-bearing).

PSII is a chlorophyll-protein complex embedded in the thylakoid membrane that uses light to oxidize water to oxygen and reduce plastoquinone to plastoquinol.

“PSII is a chlorophyll–protein complex embedded in the thylakoid membrane that uses light to oxidize water to oxygen and reduce the electron acceptor plastoquinone to plastoquinol.”

May combine two claims.

Water splitting involves four electron chemistry; four separate charge separations are required to form one molecule of O2 from two molecules of water.

“Nonetheless, since water splitting involves four electron chemistry and charge separation only involves transfer of one electron, four separate charge separations (turnovers of PSII) are required to drive formation of one molecule of O2 from two molecules of water.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Chlorophyll, carotenoids, and in cyanobacteria and some algae bilins are photosynthetic pigments that share a conjugated π-electron system.

“The most well-known of these is chlorophyll, but there are also carotenoids and, in cyanobacteria and some algae, bilins. These pigments all have in common within their chemical structures an alternating series of carbon single and double bonds, which form a conjugated system π–electron system (Figure 6).”

Probably not a substantial claim: may not pass S3 (load-bearing).

The light-driven electron transfer reactions of photosynthesis begin with the splitting of water by Photosystem II (PSII).

“The light-driven electron transfer reactions of photosynthesis begin with the splitting of water by Photosystem II (PSII).”

Probably not a substantial claim: may not pass S3 (load-bearing).

The size of the stomatal openings is regulated by a pair of guard cells that respond to the turgor pressure of the leaf.

“The size of the stomatal openings is variable and regulated by a pair of guard cells, which respond to the turgor pressure (water content) of the leaf”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The light reactions occur in the chloroplast thylakoid membrane and involve the splitting of water into oxygen, protons and electrons.

“The light reactions occur in the chloroplast thylakoid membrane and involve the splitting of water into oxygen, protons and electrons.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In land plants, the principal organs of photosynthesis are the leaves.

“In land plants, the principal organs of photosynthesis are the leaves (Figure 2A).”

Probably not a substantial claim: may not pass S3 (load-bearing).

The Calvin-Benson cycle (dark reactions) uses ATP and NADPH to convert CO2 into carbohydrate in the chloroplast stroma.

“The ATP and NADPH are then utilized by the enzymes of the Calvin–Benson cycle (the dark reactions), which converts CO2 into carbohydrate in the chloroplast stroma.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

A photosystem consists of numerous LHCs that form an antenna of hundreds of pigment molecules.

“A photosystem consists of numerous LHCs that form an antenna of hundreds of pigment molecules.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The chloroplast has two outer membranes (the envelope) enclosing an aqueous stroma, with a thylakoid membrane enclosing a lumen.

“The chloroplast has a complex structure (Figure 2C, D) with two outer membranes (the envelope), which are colourless and do not participate in photosynthesis, enclosing an aqueous space (the stroma) wherein sits a third membrane known as the thylakoid, which in turn encloses a single continuous aqueous space called the lumen.”

May combine two claims.

PSII is a light-driven water-plastoquinone oxidoreductase and is the only enzyme in Nature capable of splitting water into protons, electrons and oxygen.

“PSII is a light-driven water–plastoquinone oxidoreductase and is the only enzyme in Nature that is capable of performing the difficult chemistry of splitting water into protons, electrons and oxygen (Figure 11).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Entry of CO2 to the leaf is controlled by stomata in the lower epidermis.

“entry of CO2 to the leaf is controlled by small holes in the lower epidermis called stomata (Figure 2B).”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Chlorophylls absorb blue and red light and appear green, whereas carotenoids absorb light only in the blue and appear yellow/red.

“The chlorophylls absorb blue and red light and so appear green in colour, whereas carotenoids absorb light only in the blue and so appear yellow/red (Figure 7), colours more obvious in the autumn as chlorophyll is the first pigment to be broken down in decaying leaves.”

Probably not a substantial claim: may not pass S3 (load-bearing).

When the leaf is hydrated, the stomata can open to allow CO2 in.

“thus when the leaf is hydrated, the stomata can open to allow CO2 in.”

May combine two claims.

For excitation energy transfer to occur, the two chlorophylls must be close by (<7 nm), have a specific orientation with respect to one another, and have excited state energies that overlap.

“For this to occur, the two chlorophylls must be close by (<7 nm), have a specific orientation with respect to one another, and excited state energies that overlap (are resonant) with one another.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Photophosphorylation is essentially similar to oxidative phosphorylation.

“This process of photophosphorylation is thus essentially similar to oxidative phosphorylation, which occurs in the inner mitochondrial membrane during respiration.”

Probably not a substantial claim: may not pass S3 (load-bearing).

When water is scarce, the guard cells lose turgor pressure and close, preventing the escape of water from the leaf via transpiration.

“In contrast, when water is scarce, the guard cells lose turgor pressure and close, preventing the escape of water from the leaf via transpiration.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Photosystem I oxidizes plastocyanin and reduces ferredoxin.

“PSI oxidizes plastocyanin and reduces another soluble electron carrier protein ferredoxin that resides in the stroma.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Chlorophyll has two excited states known as S1 and S2; upon interaction with a photon, one π electron is promoted from the ground state S0 to an excited state in 10−15 s.

“Chlorophyll has two excited states known as S1 and S2 and, upon interaction of the molecule with a photon of light, one of its π electrons is promoted from the ground state (S0) to an excited state, a process taking just 10−15 s (Figure 8).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Photosynthesis begins with the absorption of light by pigment molecules located in the thylakoid membrane.

“Photosynthesis begins with the absorption of light by pigments molecules located in the thylakoid membrane.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

An endosymbiotic event between an ancestral eukaryotic cell and a cyanobacterium that gave rise to plants is estimated to have occurred ∼1.5 billion years ago.

“An endosymbiotoic event between an ancestral eukaryotic cell and a cyanobacterium that gave rise to plants is estimated to have occurred ∼1.5 billion years ago.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The reaction forms an unstable 6C intermediate that immediately splits into two molecules of 3-phosphoglycerate.

“The reaction forms an unstable 6C intermediate that immediately splits into two molecules of 3-phosphoglycerate.”

May combine two claims.

The Q-cycle involves oxidation of one plastoquinol molecule at the Qp site of the complex, and both protons from this molecule are deposited in the lumen and contribute to the proton gradient for ATP synthesis.

“The Q-cycle (Figure 14B) involves oxidation of one plastoquinol molecule at the Qp site of the complex, both protons from this molecule are deposited in the lumen and contribute to the proton gradient for ATP synthesis.”

Probably not a substantial claim: may not pass S3 (load-bearing).

PSI is found within the thylakoid membrane as a monomeric RC surrounded on one side by four LHC complexes known as LHCI.

“PSI is found within the thylakoid membrane as a monomeric RC surrounded on one side by four LHC complexes known as LHCI.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The one molecule of GAP produced per turn of the cycle can be converted into amino acids, lipids or sugars such as glucose.

“The one molecule of GAP that is produced for each turn of the cycle can be quickly converted by a range of metabolic pathways into amino acids, lipids or sugars such as glucose.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

ATP synthase is responsible for making ATP from ADP and Pi, and this endergonic reaction is powered by the energy contained within the protonmotive force.

“The ATP synthase enzyme is responsible for making ATP from ADP and Pi; this endergonic reaction is powered by the energy contained within the protonmotive force.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The cytb6f complex is a plastoquinol-plastocyanin oxidoreductase and possesses a similar structure to that of the cytochrome bc1 complex (complex III) in mitochondria.

“The cytb6f complex is a plastoquinol–plastocyanin oxidoreductase and possess a similar structure to that of the cytochrome bc1 complex (complex III) in mitochondria (Figure 14A).”

Probably not a substantial claim: may not pass S3 (load-bearing).

The electron from P700* is donated via another chlorophyll molecule and a bound quinone to a series of iron-sulfur clusters at the stromal side of the complex, whereupon the electron is donated to ferredoxin.

“The electron from P700* is donated via another chlorophyll molecule and a bound quinone to a series of iron–sulfur clusters at the stromal side of the complex, whereupon the electron is donated to ferredoxin.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Rubisco consists of eight large (56 kDa) subunits, which contain both catalytic and regulatory domains, and eight small subunits (14 kDa), which enhance the catalytic function of the large subunits.

“The complex consists of eight large (56 kDa) subunits, which contain both catalytic and regulatory domains, and eight small subunits (14 kDa), which enhance the catalytic function of the L subunits (Figure 17A).”

Probably not a substantial claim: may not pass S3 (load-bearing).

C4 plants show a specialized leaf anatomy: Kranz anatomy.

“C4 plants show a specialized leaf anatomy: Kranz anatomy (Figure 18).”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the oxygenation reaction, one rather than two molecules of 3-phosphoglycerate and one molecule of a 2C sugar known as phosphoglycolate are produced by Rubisco.

“In the oxygenation reaction, one rather than two molecules of 3-phosphoglycerate and one molecule of a 2C sugar known as phosphoglycolate are produced by Rubisco.”

Probably not a substantial claim: may not pass S4 (based).

Plants growing in hot, bright and dry conditions inevitably have to have their stomata closed for large parts of the day to avoid excessive water loss and wilting.

“Plants growing in hot, bright and dry conditions inevitably have to have their stomata closed for large parts of the day to avoid excessive water loss and wilting.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Overall the synthesis of 1 mol of GAP requires 9 mol of ATP and 6 mol of NADPH, a required ratio of 1.5 ATP/NADPH.

“Overall the synthesis of 1 mol of GAP requires 9 mol of ATP and 6 mol of NADPH, a required ratio of 1.5 ATP/NADPH.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In the first step of the Calvin-Benson cycle, CO2 is combined with ribulose 1,5-bisphosphate in a reaction catalysed by Rubisco.

“In the first step of the Calvin–Benson cycle (Figure 16), CO2 is combined with a 5-carbon (5C) sugar, ribulose 1,5-bisphosphate in a reaction catalysed by the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco).”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The FNR complex is found in both soluble and thylakoid membrane-bound forms.

“The FNR complex is found in both soluble and thylakoid membrane-bound forms.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

As with Complex III, cytb6f exists as a dimer in the membrane and carries out both the oxidation and reduction of quinones via the Q-cycle.

“As with Complex III, cytb6f exists as a dimer in the membrane and carries out both the oxidation and reduction of quinones via the so-called Q-cycle.”

Probably not a substantial claim: may not pass S3 (load-bearing).

For every three CO2 molecules initially combined with ribulose 1,5-bisphosphate, six molecules of GAP are produced by the subsequent steps.

“For every three CO2 molecules initially combined with ribulose 1,5-bisphopshate, six molecules of GAP are produced by the subsequent steps.”

Probably not a substantial claim: may not pass S3 (load-bearing).

1,3-Bisphosphoglycerate is reduced by glyceraldehyde 3-phosphate dehydrogenase using NADPH to form glyceraldehyde 3-phosphate (GAP).

“1,3-Bisphosphoglycerate is then reduced by glyceraldehyde 3-phosphate dehydrogenase using NADPH to form glyceraldehyde 3-phosphate (GAP, a triose or 3C sugar) in reactions, which are the reverse of glycolysis.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The active site in Rubisco contains a key lysine residue, which reacts with another (non-substrate) molecule of CO2 to form a carbamate anion that is then able to bind Mg2+.

“The active site in the Rubisco enzyme contains a key lysine residue, which reacts with another (non-substrate) molecule of CO2 to form a carbamate anion that is then able to bind Mg2+.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The carbon fixation step itself (the incorporation of CO2 into carbohydrate) is carried out by a single enzyme, Rubisco.

“It is noteworthy that, despite the complexity of the dark reactions outlined above, the carbon fixation step itself (i.e. the incorporation of CO2 into carbohydrate) is carried out by a single enzyme, Rubisco.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

CO2 is fixed into carbohydrate via the Calvin-Benson cycle in plants, which consumes the ATP and NADPH produced during the light reactions and thus regenerates ADP, Pi and NADP+.

“CO2 is fixed into carbohydrate via the Calvin–Benson cycle in plants, which consumes the ATP and NADPH produced during the light reactions and thus in turn regenerates ADP, Pi and NADP+.”

May combine two claims.

Malate is exported from the mesophyll cells to the bundle sheath cells, where it is decarboxylated to pyruvate, thus regenerating NADPH and CO2.

“The malate is then exported from the mesophyll cells to the bundle sheath cells, where it is decarboxylated to pyruvate thus regenerating NADPH and CO2.”

May combine two claims.

Many enzymes involved in the Calvin-Benson cycle are also involved in glycolysis, and their activity must be carefully regulated to avoid futile cycling when light is present.

“Many of the enzymes involved in the Calvin–Benson cycle (e.g. transketolase, glyceraldehyde-3-phosphate dehydrogenase and aldolase) are also involved in the glycolysis pathway of carbohydrate degradation and their activity must therefore be carefully regulated to avoid futile cycling when light is present, i.e. the unwanted degradation of carbohydrate.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Rubisco is a large multisubunit soluble protein complex found in the chloroplast stroma.

“Rubisco is a large multisubunit soluble protein complex found in the chloroplast stroma.”

May combine two claims.

The net result of stomatal closure in hot, bright and dry conditions is that the internal CO2 concentration in the leaf is very low, meaning that C3 photosynthesis is not possible.

“The net result is that the internal CO2 concentration in the leaf is very low, meaning that C3 photosynthesis is not possible.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The carboxylation reaction carried out by Rubisco is highly exergonic (ΔG°=−51.9 kJ·mol-1), yet kinetically very slow (just 3 s−1), and begins with the protonation of ribulose 1,5-bisphosphate to form an enediolate intermediate which can be combined with CO2 to form an unstable 6C intermediate that is quickly hydrolysed to yield two 3C 3-phosphoglycerate molecules.

“The carboxylation reaction carried out by Rubisco is highly exergonic (ΔG°=−51.9 kJ·mol-1), yet kinetically very slow (just 3 s−1) and begins with the protonation of ribulose 1,5-bisphosphate to form an enediolate intermediate which can be combined with CO2 to form an unstable 6C intermediate that is quickly hydrolysed to yield two 3C 3-phosphoglycerate molecules.”

Probably not a substantial claim: may not pass S3 (load-bearing).

PSII is found within the thylakoid membrane of plants as a dimeric RC complex surrounded by a peripheral antenna of six minor monomeric antenna LHC complexes and two to eight trimeric LHC complexes, which together form a PSII-LHCII supercomplex.

“PSII is found within the thylakoid membrane of plants as a dimeric RC complex surrounded by a peripheral antenna of six minor monomeric antenna LHC complexes and two to eight trimeric LHC complexes, which together form a PSII–LHCII supercomplex (Figure 11).”

Probably not a substantial claim: may not pass S3 (load-bearing).

In addition to carboxylation, Rubisco also catalyses a competitive oxygenation reaction, known as photorespiration, that results in the combination of ribulose 1,5-bisphosphate with O2 rather than CO2.

“In addition to carboxylation, Rubisco also catalyses a competitive oxygenation reaction, known as photorespiration, that results in the combination of ribulose 1,5-bisphosphate with O2 rather than CO2.”

Probably not a substantial claim: may not pass S3 (load-bearing).

In PSI, the special pair of chlorophylls are known as P700 due to their 700 nm absorption peak in the red part of the spectrum.

“In PSI, the special pair of chlorophylls are known as P700 due to their 700 nm absorption peak in the red part of the spectrum.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The active site of plastocyanin binds a copper ion, which cycles between the Cu2+ and Cu+ oxidation states following its oxidation by PSI and reduction by cytb6f.

“The active site of the plastocyanin protein binds a copper ion, which cycles between the Cu2+ and Cu+ oxidation states following its oxidation by PSI and reduction by cytb6f respectively.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The P700 species is regenerated from P700+ via donation of an electron from the soluble electron carrier protein plastocyanin.

“The P700 species is regenerated form P700+ via donation of an electron from the soluble electron carrier protein plastocyanin.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Since the product of the Calvin cycle is GAP, the pathway is often referred to as C3 photosynthesis, and plants that utilize it are called C3 plants and include many of the world's major crops such as rice, wheat and potato.

“Since the product of the Calvin cycle is GAP (a 3C sugar) the pathway is often referred to as C3 photosynthesis and plants that utilize it are called C3 plants and include many of the world's major crops such as rice, wheat and potato.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Plastoquinone has a very similar structure to that of ubiquinone (coenzyme Q10) in the mitochondrial inner membrane.

“It has a very similar structure to that of the molecule ubiquinone (coenzyme Q10) in the mitochondrial inner membrane.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The evolutionary advantage of membrane stacking is believed to be a higher efficiency of electron transport by preventing the fast energy trap PSI from stealing excitation energy from the slower trap PSII, a phenomenon known as spillover.

“The evolutionary advantage of membrane stacking is believed to be a higher efficiency of electron transport by preventing the fast energy trap PSI from ‘stealing’ excitation energy from the slower trap PSII, a phenomenon known as spillover.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The electrons yielded by P680* following charge separation are not passed directly to plastoquinone, but rather via another acceptor called pheophytin.

“The electrons yielded by P680* following charge separation are not passed directly to plastoquinone, but rather via another acceptor called pheophytin, a porphyrin molecule lacking the central magnesium ion as in chlorophyll.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Plastoquinone reduction to plastoquinol requires two electrons and thus two molecules of plastoquinol are formed per O2 molecule evolved by PSII.

“Plastoquinone reduction to plastoquinol requires two electrons and thus two molecules of plastoquinol are formed per O2 molecule evolved by PSII.”

May combine two claims.

Charge separation at P680 provides the thermodynamic driving force, whereas the manganese cluster acts as a catalyst for the water-splitting reaction.

“Thus charge separation at P680 provides the thermodynamic driving force, whereas the manganese cluster acts as a catalyst for the water-splitting reaction.”

May combine two claims.

When a second plastoquinol molecule is oxidized at Qp, a second molecule of plastocyanin is reduced and two further protons are deposited in the lumen.

“When a second plastoquinol molecule is oxidized at Qp, a second molecule of plastocyanin is reduced and two further protons are deposited in the lumen.”

May combine two claims.

PSI and ATP synthase are excluded from stacked PSII-LHCII regions by steric constraints, and thus PSII and PSI are segregated in the thylakoid membrane between the stacked and unstacked regions.

“PSI and ATP synthase are excluded from these stacked PSII–LHCII regions by steric constraints and thus PSII and PSI are segregated in the thylakoid membrane between the stacked and unstacked regions (Figure 15).”

Probably not a substantial claim: may not pass S3 (load-bearing).

The first electron from plastoquinol is transferred via an iron-sulfur cluster and a haem cofactor to the soluble electron carrier plastocyanin.

“The first is transferred via an iron–sulfur cluster and a haem cofactor to the soluble electron carrier plastocyanin (see below).”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The cytb6f complex is evenly distributed throughout the grana and stromal lamellae.

“The cytb6f complex, in contrast, is evenly distributed throughout the grana and stromal lamellae.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Reduced ferredoxin is used to generate NADPH for the Calvin-Benson cycle at a separate complex known as FNR.

“Reduced ferredoxin is then used to generate NADPH for the Calvin–Benson cycle at a separate complex known as FNR.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The active site of ferredoxin binds an iron-sulfur cluster, which cycles between the Fe2+ and Fe3+ oxidation states following its reduction by PSI and oxidation by the FNR complex.

“The active site of the ferredoxin protein binds an iron–sulfur cluster, which cycles between the Fe2+ and Fe3+ oxidation states following its reduction by PSI and oxidation by the FNR complex respectively.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Linear electron transfer is generally thought to supply ATP/NADPH in a ratio of 1.28 (assuming an H+/ATP ratio of 4.67), with the shortfall of ATP believed to be provided by cyclic electron transfer reactions.

“Linear electron transfer is generally thought to supply ATP/NADPH in a ratio of 1.28 (assuming an H+/ATP ratio of 4.67) with the shortfall of ATP believed to be provided by cyclic electron transfer reactions.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

P700* is an extremely strong reductant that is able to reduce ferredoxin, which has a redox potential of −450 mV.

“P700* is an extremely strong reductant that is able to reduce ferredoxin which has a redox potential of −450 mV (and is thus is, in principle, a poor electron acceptor).”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Plastoquinone is a small lipophilic electron carrier molecule that resides within the thylakoid membrane and carries two electrons and two protons from PSII to the cytb6f complex.

“Plastoquinone is a small lipophilic electron carrier molecule that resides within the thylakoid membrane and carries two electrons and two protons from PSII to the cytb6f complex.”

May combine two claims.

The reactions that convert phosphoglycolate consume additional ATP and thus result in an energy loss to the plant.

“These reactions consume additional ATP and thus result in an energy loss to the plant.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

ATP synthase is a rotary motor with two domains: the membrane-spanning FO portion conducts protons from the lumen to the stroma, and the F1 catalytic domain couples this exergonic proton movement to ATP synthesis.

“The enzyme is a rotary motor which contains two domains: the membrane-spanning FO portion which conducts protons from the lumen to the stroma, and the F1 catalytic domain that couples this exergonic proton movement to ATP synthesis.”

Probably not a substantial claim: may not pass S3 (load-bearing).

3-Phosphoglycerate is first phosphorylated by 3-phosphoglycerate kinase using ATP to form 1,3-bisphosphoglycerate.

“3-Phosphoglycerate is first phosphorylated by 3-phosphoglycerate kinase using ATP to form 1,3-bisphosphoglycerate.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Glucose may be stored as the polymer starch as large granules within chloroplasts.

“Glucose in turn may be stored as the polymer starch as large granules within chloroplasts.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

The PSI-LHCI supercomplex is found mainly in the unstacked regions of the thylakoid membrane.

“The PSI–LHCI supercomplex is found mainly in the unstacked regions of the thylakoid membrane (Figure 13).”

Probably not a substantial claim: may not pass S3 (load-bearing).

One such CCM is C4 photosynthesis, which is found in plants such as maize, sugar cane and savanna grasses.

“One such CCM is C4 photosynthesis that is found in plants such as maize, sugar cane and savanna grasses.”

Probably not a substantial claim: may not pass S3 (load-bearing).

To counter photorespiration, plants, algae and cyanobacteria have evolved different CO2-concentrating mechanisms (CCMs) that aim to increase the concentration of CO2 relative to O2 in the vicinity of Rubisco.

“To counter photorespiration, plants, algae and cyanobacteria have evolved different CO2-concentrating mechanisms CCMs that aim to increase the concentration of CO2 relative to O2 in the vicinity of Rubisco.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Two protons are taken up upon formation of plastoquinol and these are derived from the stroma.

“Two protons are also taken up upon formation of plastoquinol and these are derived from the stroma.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Within the thylakoid membrane, PSII-LHCII supercomplexes are packed together into domains known as the grana, which associate with one another to form grana stacks.

“Within the thylakoid membrane, PSII–LHCII supercomplexes are packed together into domains known as the grana, which associate with one another to form grana stacks.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Ferredoxin is a small soluble electron carrier protein that resides in the chloroplast stroma.

“Ferredoxin is a small soluble electron carrier protein that resides in the chloroplast stroma.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

According to the structure, 4.67 H+ are required for every ATP molecule synthesized by the chloroplast ATP synthase.

“According to the structure, 4.67 H+ are required for every ATP molecule synthesized by the chloroplast ATP synthase.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

The Crassulaceae fix CO2 into malate during the day via PEP carboxylase, store it within the vacuole of the plant cell at night and then release it within their tissues by day to be fixed via normal C3 photosynthesis.

“The Crassulaceae fix CO2 into malate during the day via PEP carboxylase, store it within the vacuole of the plant cell at night and then release it within their tissues by day to be fixed via normal C3 photosynthesis.”

May combine two claims.

For each pair of plastoquinol molecules oxidized by the cytb6f complex, one is regenerated, yet all four protons are deposited into the lumen.

“Thus for each pair of plastoquinol molecules oxidized by the complex, one is regenerated, yet all four protons are deposited into the lumen.”

Probably not a substantial claim: may not pass S3 (load-bearing).

By reducing ferredoxin and NADP+, PSI changes the redox state of the stroma, which is sensed by the regulatory protein thioredoxin.

“In addition, by reducing ferredoxin and NADP+, PSI changes the redox state of the stroma, which is sensed by the regulatory protein thioredoxin.”

Probably not a substantial claim: may not pass S3 (load-bearing).

PSI is a light-driven plastocyanin-ferredoxin oxidoreductase.

“PSI is a light-driven plastocyanin–ferredoxin oxidoreductase (Figure 13).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Kranz refers to a bundle sheath of cells that surrounds the central vein within the leaf, which in turn are surrounded by the mesophyll cells.

“Kranz, German for wreath, refers to a bundle sheath of cells that surrounds the central vein within the leaf, which in turn are surrounded by the mesophyll cells.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

Plastocyanin is a small soluble electron carrier protein that resides in the thylakoid lumen.

“Plastocyanin is a small soluble electron carrier protein that resides in the thylakoid lumen.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Under normal conditions, the ratio of carboxylation to oxygenation is between 3:1 and 4:1.

“Under normal conditions, the ratio of carboxylation to oxygenation is between 3:1 and 4:1.”

May combine two claims.

Proton gradient formation across the thylakoid membrane during the light reactions increases the pH and increases the Mg2+ concentration in the stroma.

“Proton gradient formation across the thylakoid membrane during the light reactions increases the pH and also increases the Mg2+ concentration in the stroma (as Mg2+ flows out of the lumen as H+ flows in to compensate for the influx of positive charges).”

Probably not a substantial claim: may not pass S3 (load-bearing).

Progressive extraction of electrons from the manganese cluster driven by the oxidation of P680 by light is known as the S-state cycle.

“Progressive extraction of electrons from the manganese cluster is driven by the oxidation of P680 within PSII by light and is known as the S-state cycle (Figure 12).”

Probably not a substantial claim: may not pass S3 (load-bearing).

FNR binds a flavin-adenine dinucleotide (FAD) cofactor at its active site, which accepts two electrons from two molecules of ferredoxin before using them to reduce NADP+ to NADPH.

“The complex binds a flavin–adenine dinucleotide (FAD) cofactor at its active site, which accepts two electrons from two molecules of ferredoxin before using them reduce NADP+ to NADPH.”