Botany (Photosynthesis)

These factors, as part of the C4 pathway, give C4 plants a competitive advantage over C3 plants under the above described environmental conditions.

1. C4 plants, because of the way they initially fix CO2, can maintain equal or increased photosynthetic rates over C3 plants under conditions of high temperature and dryness. 2.C4 plants need to have their stomata open much less than C3 plants to fix an equal amount of carbon. Also, C4 plants tend to have smaller stomata than C3 plants which dramatically reduces water loss from transpiration

The CAM pathway occurs in two principal plant families:

1. Cactaceae = cactus family 2. Crassulaceae (in part) = stonecrop family

Two other classes of pigments capture light energy for photosynthesis. (not Chlorophylls)

1. carotenoids Two classes: a. carotenes: orange, red, and occasionally purple pigment molecules which lack oxygen in their molecular structure (Fig). b. xanthophylls: yellow pigment molecules which have oxygen in their molecular structure (Fig). 2. phycobilins water soluble, red or blue, photosynthetic pigments found in some of the red algae and in many types of bacteria, including cyanobacteria

The energy from the excited state of the electron has three possible fates:

1. energy is converted to heat or heat and light. The light that is produced is of a longer wavelength than that of the original excitation wavelength and is known as fluorescence;2. energy can be transferred to a neighboring/adjacent pigment molecule. This is known as resonance energy transfer or inductive resonance and occurs through excitation transfer of energy. Energy may be transferred to or across several pigment molecules. 3. the electron itself may be transferred to a neighboring/adjacent pigment molecule (Fig). Only 2 and 3 are useful to plants.

Hydrogen ions are transported into the thylakoid lumen from two sources:

1. from water 2. from the stroma

Some important C4 grasses include:

1. sugar cane = Saccharum officinale 2. corn = Zea mays 3. sorghum (milo) = Sorghum bicolor The C4 pathway occurs in more than 1,500 species of plants distributed over 18 or 19 different families.

Characteristics of C3-C4 intermediates:

1. they have kranz-like anatomy 2. partially suppressed photorespiration 3. reduced sensitivity to O2

The cytochrome complex consists of:

1. two cytochrome b6 cytochromes 2. an FeS iron and sulfur containing protein 3. cytochrome f (is really a c-type cytochrome)

There are about __ chlorophyll and __ or __ xanthophyll molecules associated with each CAB protein. Most higher plants contain about twice as much chlorophyll A as chlorophyll B.

10; 2 or 3

Oxidation of 2HOH yields O2, ____H+ deposited into the lumen, and 4 electrons which are ultimately transferred to 2NADP+ to produce 2NADPH via reduction of NADP+ .

12

Where ___photons are required per electron removed from water (a total of four photons to oxidize ___ water molecule), and ___ photons are required by both photosystem (2 for PSII and 2 for PSI). These latter 4 photons excite the four electrons of the two photosystems that were originally taken from water.

2,1,4

. Krebs cycle (oxidation of two molecules of pyruvate) ___ATP __NADH (____ of the 32 ATP molecules produced by the electron transport chain; remember that some NADPH can also be made when isocitrate is decarboxylated to form alpha-ketoglutarate) ___FADH2 (____of the 32 ATP molecules produced by the electron transport chain) ____CO2

2,6,18,2,4,4

2. Pyruvate to acetylCoA (for two molecules of pyruvate) ___ NADH (yields ___ ATP later from the electron transport chain) ___ CO2 ___ acetate (combines with CoA to form acetylCoA) before entering the Krebs cycle

2,6,2,2

The net photosynthetic rates for C4 species are __-__ times higher than for C3 species.

2-3

For each hexose phosphate oxidized, a total of _____electrons (12 electron pairs) are generated. _______ electrons (10 electron pairs) are stored in 10 molecules of NADH and ___electrons (2 electron pairs) are stored in 2 molecules of FADH2. Both NADH and FADH2 are high-energy molecules, which will be used to generate ATP in the process of oxidative phosphorylation through the respiratory electron transport chain. The aerobic oxidation of one molecule of hexose phosphate provides about ______kj of energy and generates _____ (ca. ____ net) molecules of ATP. This represents an efficiency of about ____%.

24 electrons, twenty, 4, 2750 kj. 38, 36. 94

____________ of the 36 ATP molecules produced are produced from the electron transport chain. The electrons that NADH and FADH2 transport from the Krebs cycle are used to generate ___ molecules of ATP by the electron transport chain. NADH from glycolysis and the oxidation of pyruvate to form acetylCoA (for two molecules of pyruvate) generate ____molecules of ATP by the electron transport chain. Electrons are transported from NADH, FADH2, and NADPH to O2 to produce HOH and ATP.

32, 22, 10

Oxidative electron transport chain ____ATP ____ HOH

32, 32

Because hydrogen ions are continually being added to the lumen and removed from the stroma, a large pH gradient forms across the thylakoid membrane. This electrochemical gradient has tremendous potential energy. The pH of the lumen is ___ or ___, while the pH of the stroma is about __. Because pH is logarithmic in scale and function, there is _______ to _________ times more protons in the lumen then in the stroma. Remember, pH is the negative log of the H+ ion concentration. As pH goes up, there are less H+ ions present in solution. As pH goes down, there are more H+ ions in solution (

4 or 5, 8, 1000-10,000

1. Glycolysis ___total ATP, ___ net (___ net ATP if the hexose sugar entering glycolysis is phosphorylated) __ NADH (yield ___ATP later from the electron transport chain)

4, 2, 3. 2, 4

the primary range of light that plants use for photosynthesis?

400-740/750nm—spectrum of visible light

In the Calvin cycle, CO2 is fixed initially into a __-_______ _______ __________, which immediately decomposes into two molecules of ______. So in practicality, CO2 is initially fixed into triose sugars. The Calvin cycle occurs in the stroma of the chloroplast in most photosynthetic organisms

6-carbon unstable compound;3-PGA

The efficiency of the Calvin cycle is about ___%; the entire process of photosynthesis is only about ___%.

90%;33%

The water vapor concentration inside the leaf is about ____%(essentially 100%). The leaf mesophyll cells are actually covered in a thin film of water which allows CO2 to become hydrated (HCO3 - ) and diffuse into the cells across the plasmalemma. Membranes are essentially impermeable to gasses

99.7%

Regeneration (calvin cycle)

: regeneration of ribulose 5-phosphate into ribulose 1,5-phosphate (ribulose bisphosphate). This process requires another molecule of ATP (Fig). For each molecule of CO2 fixed in the Calvin cycle, two molecules of NADPH and three molecules of ATP are required.

two classes of pigments that are water soluble

Anthocyanins and betacyanins; These two classes of pigments are generally not considered photosynthetic

Plastocyanin transports its electron along the thylakoid lumen to P700 of PSI. P700 must be oxidized by a photon of light to P700+ before it can accept an electron from PC. P700+ is reduced by PC to P700 and P700 once struck by a photon, passes its electron in the excitation state to _____—a modified chlorophyll A, which is similar to pheophytin then passes its electron to _____—_____________ (vitamin K). A1 then passes its electron to a series of three iron and sulfur containing proteins known as Fe-S centers: ______, _______, and _______, which are similar to the FeS protein of the cytochrome b6-f complex.

Ao; A1; phylloquinone; FeSX, FeSA, FeSB

Basic equation for respiration:

C6H12O6 + 6 O2 + 6 HOH ————— 6 CO2 + 12 HOH + energy (ATP)

Carboxylation

CO2 enters the cycle and is fixed in the presence of the enzyme ribulose bisphosphate carboxylase/oxygenase (rubisco). The resultant 6-carbon compound from the incorporation of CO2 into ribulose bisphosphate is immediately hydrolyzed into two molecules of 3-PGA. The first detectable compound of the Calvin cycle is a 3-carbon sugar—thus, the Calvin cycle is also known as the C3 pathway. Plants that initially fix carbon into 3-carbon molecules are known as C3 plants (

Electrons move from water to manganese and from manganese to tyrosine in the D1 protein and down the chain to ultimately reduce NADP+ to NADPH. e- e- e- e- HOH PS II (including OEC) cytochrome b6-f complex PSI INADP+ = NADPH 2HOH + 2NADP+ + light energy ————— 2NADPH + 4H+ + O2 ________ and ________ (chemical ions?) are also essential for the oxidation of water. The tyrosine in the D1 protein passes the electrons one at a time to _______, which is a special molecule of chlorophyll A in PSII that is intricately associated with the thylakoid membrane, and because of this, has a peak absorption of light at 680nm. In PSI, a similar molecule of chlorophyll A known as ______ has an absorption peak at 700nm.

Calcium ions (Ca2+); chloride ions (Cl-); P680; P700

the green class of pigments of photosynthetic organisms, primarily absorbs light in the violet, blue, and red wavelengths and reflects or transmits green, and to some extent, yellow wavelengths.

Chlorophyll

CAM pathway (step by step)

Co2 in the form of bicarbonate is fixed into PEP by PEPC into OAA, is reduced to malate then malic acid, stored in vacoule; pumped out, the next day and converted back to malate, makes NADH or NADPH, decarboxylated into pyruvate and Co2 which goes to the C3 cycle and pyruvate is used for metabolic needs or converted back into PEP

The proteins of the cytochrome complex are iron (Fe) containing proteins. They use the multiple oxidation states of iron to allow for redox reactions to occur. In their reduced form, iron is in the ferrous form ____, when oxidized, iron is in the ferric form____ .

Fe2+, Fe3+

Light-independent reactions, Calvin cycle, C3 cycle, or carbon fixation reactions ( give a brief overview)

Here, CO2 is fixed into carbohydrate initially as 3-PGA, where 3-PGA is converted to 3-PGAL and dihydroxyacetone phosphate (DHAP) and used to make carbohydrates such as glucose and sucrose, and other complex biomolecules, including amino acids, proteins, RNA, DNA, and carbohydrate polymers such as starch, pectins, and cellulose.

CO2 fixation was first discovered by the plant physiologist _______ _______. The atmospheric concentration of CO2 is about ______-_____%. Additionally, CO2 and HCO3 - dissolved in water can also be used for photosynthesis

Melvin calvin; 0 36-0.04%

one reason C4 plants use available CO2 more efficiently than do C3 plants.

One reason is that PEP carboxylase activity is not reduced or hindered by the presence and availability of O2

process of photorespiration

Ribulose-1,5-bisphosphate is converted to a 5-carbon compound with O2 as part of its structure (Fig.). This 5-carbon compound decomposes into one molecule of 3-PGA and a 2-carbon molecule, phosphoglycolate (Fig.). Phosphoglycolate is metabolized in a series of enzyme mediated reactions that occur in the chloroplast, peroxisome, and mitochondrion, with the subsequent release of one molecule of CO2, and the remaining carbons eventually forming glycerate. Glycerate is phosphorylated to form 3-PGA, and returned to the Calvin cycle.3-PGA is immediately transported back to the Calvin cycle for use in the carbon fixation reactions, while glycolate is ultimately converted into the amino acids glycine, and finally serine. Photorespiration is known alternatively as the oxidative photosynthetic carbon cycle, photosynthetic carbon oxidation cycle (PCO) or the C2 glycolate cycle because glycolate is a 2-carbon molecule.

The starting molecule in the Calvin cycle

RuBP or ribulose 1,5- bisphosphate

photophosphorylation.

The potential energy of this gradient is converted to kinetic energy, and used in the production of ATP with sunlight

The light-dependent reactions or photosynthetic electron transport chain consists of ?

This consists of the oxygen evolving complex (part of photosystem II), photosystem II, the cytochrome complex, and photosystem I. Oxygen gas (O2), ATP, and NADPH (Fig) are formed during these reactions.

Photosynthetic bacteria, other than the cyanobacteria, contain other photosynthetic pigments.

a. bacteriochlorophyll b. chlorobium chlorophyll; Chlorobium chlorophyll is found in the green sulfur bacteria. These bacteria cannot extract electrons from water and do not produce oxygen gas as a bi-product of photosynthesis. Instead, they use hydrogen sulfide (H2S) as an electron source and give off sulfur gas

These light harvesting or antenna pigments (chlorophyll A, chlorophyll B, and xanthophyll, probably mostly lutein) _______ and _________ light energy to the reaction center at a very high rate via inductive resonance.

absorb and transmit

The chlorophyll B, chlorophyll C , the carotenoids, and the phycobilins are known as

accessory pigments

ATP and NADPH are expended during photorespiration, one atom of carbon is lost as CO2, and one molecule of _________ +1) is formed +1 is recovered via the ____________ ________ _______, which is closely tied to photorespiration and is part of _________ ____________ in the plant. Photorespiration does produce some NADH (nicotinamide adenine dinucleotide

ammonium; photorespiratory nitrogen cycle; nitrogen metabolism

The PSII and PSI reaction centers have numerous ___________ (accessory) pigments consisting of chlorophylls (_______ ________) and carotenoids that are intimately associated with ___________-_______ (CP) complexes.

antennae; antennae chlorophyll; chlorophyll-protein

The most important function of the carotenoids

as anti-oxidants which prevent photooxidative damage to the chlorophyll molecules. Carotenoids act as quenching agents for free-radical oxygen during conditions when photosynthesis is occurring at extremely high rates. The carotenoids keep the chlorophyll molecules from breaking down under these conditions. Plants cannot photosynthesize without the presence of carotenoids which stabilize chlorophyll. Chlorophyll is an unstable molecule and must constantly be maintained and produced within the plant to maintain an adequate level of chlorophyll for photosynthesis. The carotenoids are also important in the coloration of flowers and fruits in attracting animals for pollinator of flowers and dispersal of fruit and seed.

three stages of calvin cycle or c3 cycle

carboxylation, reduction and regeneration

Which kind of chlorophyll pigment occurs in all photosynthetic eukaryotes and the cyanobacteria. It is essential for oxygen generating photosynthesis. It is blue-green in color and has a terminal methyl (CH3) group.

chlorophyll A

which Chlorophyll pigment is an accessory pigment and occurs in plants, green algae, and euglenoids. It is yellow-green in color and has a terminal aldehyde (COH) group

chlorophyll B has a slightly different absorption spectrum than chlorophyll A. Chlorophyll B broadens the range of light that can be used by the plant in photosynthesis. Chlorophyll B transmits its energy to chlorophyll A during photosynthesis.

this chlorophyll pigment acts as a accessory pigment in certain types of algae. Not found in higher plants

chlorophyll C takes the place of chlorophyll B in certain types of algae. 1. brown algae 2. diatoms

neither of these additional kinds of chlorophyll pigments are found in higher plants.

chlorophyll D and chlorophyll E

The above complex is known as the PSII light harvesting complex (LHCII). Each pigment molecule is associated with an integral protein of the thylakoid membrane. These proteins are specifically known as _____________ _____ ________ ________or CAB proteins

chlorophyll a/b binding proteins

No carbon is fixed during the process of photorespiration, and additional energy must be added in order to salvage the carbons from phosphoglycolate. The pathway to carbon recovery involves the __________, __________, and ___________.

chloroplast, peroxisomes and mitochondria

Ancestral photosynthetic organisms, including most photosynthetic bacteria, only used ______ _______ _____. ________ _______ ________is more advanced.

cyclic electron flow; noncyclic electron flow

Alternatively, electrons transported by ferredoxin can, instead of reducing NADP+ , cycle back to P700 or farther up the chain to one of the quinone electron carriers. From P700 or one of the various quinones, the electrons make their way back down the chain to ferredoxin again and the process starts all over. This is known as ________ _________ _____________. No water is split and oxidized, no oxygen gas is produced, and no NADPH is formed, but protons are still transported into the thylakoid lumen. This allows PSI to work independently of PSII. The corresponding ATP production is known as _________ ________________.

cyclic electron transport; cyclic photophosphorylation

The Q cycle Two molecules of PQH2 now transport four electrons (two per PQH2 molecule) to the _______ _______ ______, and sequentially bind with it, simultaneously reducing the ______ (iron and sulfur containing protein) and the cytochrome b6 portion of the complex Also at this time, the two molecules of PQH2 deposit ______ protons (two per molecule) into the thylakoid _______. Once the two molecules of PQH2 have reduced the cytochrome b6-f complex, they are oxidized and become ______ (molecule name?). One of the molecules moves up along the cytochrome complex to receive two more electrons and two more protons, the other molecule returns to the QB binding site on the ____ protein.

cytochrome b6-f complex; FeS; four; lumen; PQ; D1

Glycolysis in plants occurs

cytosol, chloroplasts, and amyloplasts.

They, like C4 plants, have both the C3 and C4 pathways, but in CAM plants, there is a temporal separation between the two pathways. This is separation in time. CAM plants fix CO2 in the ______through the activity of PEP carboxylase in the cytosol.

dark

lycolysis Glycolysis is the first stage of respiratory carbon metabolism, where hexose sugars are partially oxidized to form the three-carbon acid, pyruvic acid or pyruvate. Glycolysis is believed to be the most ancestral type of carbon metabolism. Glycolysis leads to pyruvate in the presence of diatomic oxygen (aerobic respiration), and alcohol and lactic acid in the absence of oxygen (anaerobic respiration). This process is known as _________.

fermentation

Mobile iron and sulfur containing proteins known as ferredoxins (Fd) which are only loosely attached to the stroma side of the thylakoid membrane are reduced one electron at a time. Once reduced, it transports one electron to NADP+ , partially reducing it (forms ½NADPH). A second Fd then transports another electron to NADP+ (½NADPH), fully reducing it to NADPH. Reduction of NADP+ by Fd is facilitated by a small __________ _________.

ferredoxin; flavoprotein ezyme

Anthocyanins are ___________ (type of phenolic); Anthocyanins are usually______ , ______, or _____in color; The anthocyanins have their basic molecular structure as a pair of 6-carbon aromatic rings linked to a third by a 3-carbon chain (Fig). Each carbon ring has alcohol groups at various positions. Technically, the basic structure described above is an anthocyanidin, and anthocyanidins are converted to anthocyanins in the plant by adding various types of sugars (ex. glucose, galactose, etc.) to various positions on the molecule. Are stored in the _______and their color (anthocyanins) is often dependent on the pH of the solution within it. The anthocyanins are the most important group of pigments in producing flower color in angiosperms. They are also important in shielding new growth and tender portions of the plant from ________ ________. Because of the double bond character of the molecules, the energy in ______ ________ is absorbed by the anthocyanin molecule and is blocked from tender tissues

flavonoids; red; blue; violet; vacuoles; ultraviolet radiation; UV radiation

For each pair of water molecules oxidized, _____ electrons are carried by the quinones (____ electrons per quinone).

four, two

In the Krebs cycle, pyruvate is completely oxidized to ________ _____ and ______ The ________are temporarily stored as reducing power in NADH or FADH2. ________ is not actually part of the Krebs cycle proper, and is oxidized to acetate and ultimately acetyl coenzyme A (accetylCoA) before entering the cycle. Pyruvate does provide the essential link between glycolysis and the rest of carbon metabolism. It takes _____turns of the Krebs cycle to metabolize or fully oxidize one molecule of hexose phosphate.

free electrons, CO2, HOH. FE, PY, two

These ATP synthase enzyme complexes create ion channels that selectively allow protons to cross the thylakoid membrane in a controlled manner. As the protons move from a region of high concentration to low concentration, energy must be released. The protons are moving from a state of high potential energy to a state of low potential energy. To get there, the protons must release some _____ ________. The ATP synthase enzyme uses some of this free energy given off by the protons as they move down the electrochemical gradient across the thylakoid membrane, and couples it to the formation of ATP which requires the input of energy (Fig). This type of ATP synthesis that occurs in chloroplasts and also mitochondria is termed ____________. The synthesis of one molecule of ATP by ATP synthase in the chloroplast requires the movement of three H+ ions across the thylakoid membrane from the lumen to the stroma.

free energy; chemoismosis

Lipids and proteins (proteins are converted to organic acids first) can also be converted into sugars via __________ or ______ ________ for use as substrate for respiration.

gluconeogenesis; reverse glycolysis

Oxidative (respiratory) electron transport chain Most of the energy from hexose phosphate has been stored as ___________ from the oxidation of the initial hexose sugar, and used for the production of glycolytic and Krebs cycle intermediates and molecules.

high energy electrons

Because of the oxygenase activity of rubisco, the name ribulose bisphosphate carboxylase/oxygenase (rubisco) was awarded to this enzyme. Photorespiration can only occur in the _______ ____ _______. O2 is consumed, CO2 is released, and no ATP or NADPH are produced. In some C3 plants, as much as ____% of the carbon fixed during photosynthesis is oxidized to CO2.

in the presence of light; 50%

P680 in the PSII core complex also receives light energy by ________ _________ from a total of about _______chlorophyll A and chlorophyll B molecules, along with numerous carotenoids, especially xanthophylls

inductive resonance; 250

This ring of mesophyll cells surrounding a ring of bundle sheath cells characteristically found in C4 plants is known as _______ anatomy and is the German word for ______

kranz; wreath

Photosynthesis is the route to which nearly all energy is incorporated into the biosphere, and it is the __________ synthetic process on earth.

largest

The best equation for photosynthesis is

light energy 3CO2 + 6HOH ———————— C3H6O3 + 3O2 + 3HOH chlorophyll and carotenoid pigments ribulose-bisphosphate carboxylase/oxygenase (rubisco)

Most C4 species are _________, especially grasses = Poaceae and sedges = Cyperaceae. However, there are over 300 species of ________ which have the C4 pathway.

monocots,eudicots,

betacyanins are aromatic, _________ compounds; the betacyanins are mostly _____or _____in color; The betacyanins occur in a group of closely related families of angiosperms in the order Chenopodiales: Cactaceae (cactus family), Chenopodiaceae (goosefoot family), Amaranthaceae (pigweed family), Portulacaceae (purslane family), Nyctaginaceae (four-o'-clock family), and others). These compounds are aromatic, more complex than the anthocyanins, and take their place in these taxa. The red and purple coloration of rhubarb and sugar beets is because of betacyanins

nitrogenous; yellow; red

The light driven reactions by which electrons are transferred across thylakoid membranes via numerous electron carriers through a consecutive series of oxidation/reduction reactions to ultimately form NADPH are known as _________ _________ _______________, because the electrons do not cycle back to water. The electrons are transferred to NADP+ , thus reducing it to NADPH. it is unidirectional flow of electrons from water to NADP+ . The corresponding ATP production that occurs is known as _________ ________________.

noncyclic electron transport; noncyclic photophosphorylation

P680 can only accept electrons _____ at a time. Light oxidizes P680 into P680+ (has lost one electron). P680+ then acts as an oxidant and pulls one electron from the __________ molecule in the ____ protein. The now oxidized tyrosine pulls an electron from a ________ atom in the OEC. P680 passes its electron to a modified chlorophyll A molecule known as __________ (Pheo), where the __________(Mg) atom has been replaced by two hydrogen atoms (Fig). A photochemical conversion reaction (the conversion of the energy of sunlight into chemical energy that is initially stored as redox energy) occurs when P680 passes its excited electron to (reduces) Pheo, creating P680+ and Pheo-.

one; tyrosine; D1; manganese; pheophytin; magnesium.

About 10-25% of hexose sugars (as glucose in this case) are oxidized initially via the _________ ________ _________ _________. This pathway occurs in the chloroplast and the cytosol during night periods.

oxidative Pentose phosphate pathway

Hexose sugars must be ___________ to enter glycolysis. The cytosolic hexose phosphate pool consists of 1. glucose-1-phosphate, 2. glucose-6-phosphate, and 3. fructose-6-phosphate. All of these will be converted to ________-_____-__________ upon entering glycolysis.

phosphorylated; fructose 1,6 bisphosphate

Aerobic (oxygen using) respiration is the process where ____________(high energy carrying molecules, such as sugars produced from photosynthesis, are oxidized to produce ATP energy. The ATP produced from respiration is used to drive many of the metabolic processes that occur in the cell. Cellular respiration can be divided into three portions: glycolysis, the Krebs cycle, and the oxidative electron transport chain

photoassimilates

NOTE: all of the molecules of chlorophyll and carotenoids of the photosystem can absorb photons, but only a few can __________ or ___________ light energy into chemical energy. These would be the reaction center pigments P680 and P700.

photoconvert or transduce

The C2 pathway involves complex interactions between __________, ____________, and _________ ___________

photosynthesis; respiration and metabolism

C4 pathway

plants initially fix CO2 in the form of bicarbonate (HCO3 - ). Bicarbonate is one of the hydrated forms of CO2, the other is carbonic acid (H2CO3). 3HOH + 2CO2 ————— HCO3 - + H2CO3 + H3O+ (hydronium ion).HCO3 - is initially fixed into phosphoenolpyruvate (PEP) in the presence of the enzyme phosphoenolpyruvate carboxylase (PEPC) to form the 4-carbon compound oxaloacetate (Fig). Subsequently, oxaloacetate is converted into either malate by replacing the carbonyl on carbon 2 with an alcohol functional group, or aspartate by adding an amino group to carbon 2 and loss of the carbonyl (Fig). These reactions occur in the chloroplasts of the mesophyll cells. Next, the malate or aspartate is transported to the bundle sheath cells where they are decarboxylated to form CO2 and pyruvate (malate) or CO2 and alanine (aspartate) (Fig). The CO2 now enters the Calvin cycle which is only run in the bundle sheath cells and is fixed into ribulose bisphosphate by rubisco just as in C3 plants. The pyruvate or alanine returns to the mesophyll cell (alanine is converted to pyruvate in the mesophyll cell) where it reacts with ATP to regenerate or reform PEP

Once the electrons have been passed to cytochrome f, cytochrome f reduces the mobile, copper containing protein ____________ (PC) with one electron. Reduced PC has copper (Cu) in its cuprous form Cu+ and when oxidized, PC has copper in the cupric form Cu2+ .

plastocyanin

When QA transfers its two electrons to QB, QB also acquires two protons from the stroma. Once QB is reduced with two electrons and two associated protons, it leaves the D1 protein, and becomes the mobile electron carrier ___________ (PQH2). As soon as the reduced QB (PQH2) leaves the D1 protein, an oxidized PQ replaces it at that open site on the D1 protein. QB becomes PQH2 upon reduction and leaving the D1 protein, PQH2 becomes PQ upon oxidation, and when PQ reattaches to the D1 protein, it is ready to receive two more electrons and two more H+ ions

plastoquinol

Prep step and Krebs cycle (Step by Step)

pyruvate lose CO2, are converted into acetate, reduces NAD+ and binds to CoA and makes acetylCOa, binds with OAA and releases CoA to make citrate (first Product) makes NADH or NADPH, turns into isocitrate loses CO2 by isocitrate dehydrogenase and forms alpha-keto glutarate. binds with CoA and loses CO2 to make succinyl CoA then loses CoA makes ATP and Succinate reduces FADH2 and forms fumarate through succinate dehydrogenase then forms malate which makes NADH to form OAA

Pheophytin then rapidly transfers its electron to a _______ known as ____. strongly associated with the ____ protein. accepts two electrons sequentially from Pheo, then transfers its two electrons, one at a time, to another quinone known as _____or __________ (PQ) that is attached to the QB binding site on the protein. QB is only loosely attached to the D1 protein. To fully reduce QA and QB, it takes two electrons each. Two protons (H+ ions) are acquired from the stroma by QB, and accompany each pair of electrons that are transferred to QB by QA

quinone; QA, ; D2; QB;Plastoquinone; QB; D1

P680 and P700 are known as ________-_______ _________. Both P680 and P700 occur as part of a photosystem core comprised of various pigments, electron carriers, and proteins associated to the thylakoid membranes (comprising each of the two photosystems: PSII and PSI).

reaction-center pigments

Photorespiration (step by step)

ribulose 1,5 bisphosphate fixes O2 in the presence of Rubisco into a five carbon sugar which converts into 3-PGA and phosphoglycolate. the 3-PGA goes to the calvin cycle; the other one loses a inorganic phosphate and OH to form glycolate and eventually turns into glycerate and is phosphorylated to form 3-PGA

Photorespiration occurs when

rubisco binds O2 instead of CO2 at its active site.

For each molecule of water that is oxidized by the OEC, ____ protons are deposited into the thylakoid lumen. ____directly from water and _____ from the stroma which are carried to the lumen by 2PQH2

six, two, four

Some of the 3-PGAL are used in the chloroplast to form _______ molecules which is the main product formed when photosynthesis is occurring at high rates

starch

There is a LHCI for PSI, and PSI is exclusively located in the ________ ___________ and nonappressed regions of the grana that face the stroma.

stroma thylakoids

glycolysis (step by step)

sugars are broke down into fructose 1,6 BP is turned into 3-PGAL and DHAP (which is converted to 3-PGAL), reduces NAD+ and gains an inorganic phosphate group and is 1,3 bis PGA, makes a substrates level phos. ATP. is converted to 3-PGA then 2-PGA makes another ATP and is converted to pyruvate. happens 2x

Essentially photorespiration is absent in C4 plants because

the Calvin cycle and rubisco are isolated from any appreciable levels of O2 which competes with CO2 for the active site in rubisco.

Both noncyclic and cyclic electron flow drives the? This creates a pH and electrochemical gradient of tremendous potential energy with which to produce ATP.

the transport of protons across the thylakoid membrane into the lumen

Reduction (Calvin Cycle)

this reduction is done indirectly, where first, 3-PGA is phosphorylated by ATP into 1,3-bis-PGA, and second, 1,3-bis-PGA is reduced by NADPH to form 3- phosphoglyceraldehyde (3-PGAL) (Fig). This is the only reduction step in the Calvin cycle. 3-PGAL can be converted via a rearrangement into another important triose sugar, dihydroxyacetone phosphate (DHAP)

Numerous bound quinones are also present in these reaction centers and all molecules are integrally associated with a complex of proteins. These photochemical reaction centers are also known as ____________ ________ _________.

transducing pigment complexes

the primary carbohydrates produced from photosynthesis?

triose sugar

Under conditions of high irradiance and temperature, C4 plants can photosynthesize more rapidly and efficiently than C3 plants. They produce substantially more biomass than a C3 plant would under those conditions. They are also able to maintain active photosynthesis even under water stress. True or false

true

CO2 fixation in C4 plants has a higher energy cost than in C3 plants. For each CO2 fixed in the C4 pathway, _____molecules of ATP are required to generate PEP. Therefore, a total of __molecules of ATP are required to fix _____molecule of CO2 in the C4 pathway.

two; 5, 1