PHOTOSYNTHESIS

CAM (___ ____ ____m) plants Adaptation to ___,____ ____ ●separate ____ from Calvin cycle by ___ -close __ during ___ -open ___ during ___ ●at night: do what? ●in day: release.... -increases concentration of __ in ____ ●exs C4 vs CAM solves ___ vs ___ challenge C4- CAM- Why the C3 problem? Possibly _____ baggage ●Rubisco evolved in ____ atmosphere -there wasn't strong ___ against Today it makes a difference ●___% O2 vs. _____% CO2 ●photorespiration can ____ _____% of _____ by Calvin cycle on a ____ day ●strong ____ pressure to ____ to fix A second look inside a leaf.... Gas exchange and water flow -___ in for ___ ____ -___ out - ___ for ___ reactions -____ out ...for ___ reactions C4 photosynthesis _____ separated _____n from ____e ●____ cells -___ reaction & ____ -pumps —- to —— -keeps — away from —— -away from —-!!!!! ●Inner cells -undergo ____ ●_____ to veins

CAM (Crassulacean Acid Metabolism) plants Adaptation to hot, dry climates ●separate carbon fixation from Calvin cycle by TIME ●close stomates during day ●open stomates during night ●at night: open stomates & fix carbon in 4C "storage" compounds ●in day: release CO2 from 4C acids to Calvin cycle ●increases concentration of CO2 in cells ●succulents, some cacti, pineapple C4 vs CAM solves CO2 / O2 gas exchange vs. H2O loss challeng C4-separate 2 steps of C fixation anatomically in 2 different cells (mesophyll cell and bundle sheath cell CAM- separate 2 steps of C fixation temporally =2 different times night vs. day Why the C3 problem? Possibly evolutionary baggage ●Rubisco evolved in high CO2 atmosphere ●there wasn't strong selection against active site of Rubisco accepting both CO2 & O2 ●Today it makes a difference ●21% O2 vs. 0.03% CO2 ●photorespiration can drain away 50% of carbon fixed by Calvin cycle on a hot, dry day ●strong selection pressure to evolve better way to fix carbon & minimize photorespiration A second look inside a leaf.... Gas exchange and water flow -co2 in for calvin cycle -o2 out - waste for light reactions -H2o out ...for light reactions C4 photosynthesis PHYSICALLY separated C fixation from Calvin cycle ●Outer cells ●light reaction & carbon fixation ●pumps CO2 to inner cells ●keeps O2 away from inner cells ●away from RuBisCo ●Inner cells ●Calvin cycle ●glucose to veins

Carbon enters the Calvin cycle in ____ and leaves in ___. The cycle spends ____ as an ____ and consumes ____ as ____ power for ____s to make ____. As mentioned in Concept 8.1, the carbohydrate produced directly from the Calvin cycle is not ___. It is actually a ___). For net synthesis of one molecule of ____, the cycle must take place ____, fixing ____ . (Recall that the term carbon fixation refers to the _____ into_____l.) As we trace the steps of the Calvin cycle, keep in mind that we are following _____ through the reactions.

Carbon enters the Calvin cycle in CO2 and leaves in sugar. The cycle spends ATP as an energy source and consumes NADPH as reducing power for adding high-energy electrons to make sugar . As mentioned in Concept 8.1, the carbohydrate produced directly from the Calvin cycle is not glucose. It is actually a three-carbon sugar named glyceraldehyde 3-phosphate (G3P). For net synthesis of one molecule of G3P, the cycle must take place three times, fixing three molecules of CO,-one per turn of the cycle. (Recall that the term carbon fixation refers to the initial incorporation of CO, into organic material.) As we trace the steps of the Calvin cycle, keep in mind that we are following three molecules of CO, through the reactions.

In the Scientific Skills Exercise, you will work with data to see how different concen- trations of CO, affect growth in plants that use the C, pathway versus those that use the C, pathway. A second photosynthetic adaptation to arid conditions has evolved in___,____,____, AND many ____plants, such as aloe and jade plants These plants ___ and ____, the reverse of how other plants behave. Closing ___during the ____helps ___, but it also ____ During the night, when____, these plants ____. This mode of carbon fixation is called ____ after the plant family ____, the succulents in which the process was first discovered. The ____of CAM plants store the ____ they make during the____ in their ____until morning, when the ____ During the day, when the light reac- tions can supply ____ and ____ for the ___, ____ is released from the ____s made the night before to become incorporated into ____ in the chloroplasts. The CAM pathway is similar to the C4 pathway in that ___ is first ____ into _____ before it enters the Calvin cycle. The differ- ence is that in C4 plants, the initial steps of carbon fixation are _____ from the ____whereas in CAM plants, the two steps occur ____ but at___s. Keep in mind that CAM, C4, and C3 plants all ____ to make ___ from _____.) In this chapter, we have followed photosynthesis from _ to _. The light reactions _____and use it to make ____ and transfer electrons from ____ to ____*, forming _____. The Calvin cycle uses the ___ and ___ to produce __ from ____.

In the Scientific Skills Exercise, you will work with data to see how different concen- trations of C02 affect growth in plants that use the C4 pathway versus those that use the C3 pathway. A second photosynthetic adaptation to arid conditions has evolved in pineapples, many cacti, and other succulent (water- storing) plants, such as aloe and jade plants These plants open their stomata during the night and close them during the day, the reverse of how other plants behave. Closing stomata during the day helps desert plants conserve water, but it also prevents CO, from entering the leaves. During the night, when their stomata are open, these plants take up CO, and incorporate it into a variety of organic acids. This mode of carbon fixation is called crassulacean acid metabolism (CAM) after the plant family Crassulaceae, the succulents in which the process was first discovered. The mesophyll cells of CAM plants store the organic acids they make during the night in their vacuoles until morning, when the stomata close. During the day, when the light reac- tions can supply ATP and NADPH for the Calvin cycle, CO, is released from the organic acids made the night before to become incorporated into sugar in the chloroplasts. The CAM pathway is similar to the C, pathway in that carbon dioxide is first incorporated into or- ganic intermediates before it enters the Calvin cycle. The differ- ence is that in C4 plants, the initial steps of carbon fixation are separated structurally from the Calvin cycle, whereas in CAM plants, the two steps occur within the same cell but at separate times . (Keep in mind that CAM, C4, and C, plants all eventually use the Calvin cycle to make sugar from carbon dioxide.) In this chapter, we have followed photosynthesis from pho- tons to food. The light reactions capture solar energy and use it to make ATP and transfer electrons from water to NADP*, forming NADPH. The Calvin cycle uses the ATP and NADPH to produce sugar from carbon dioxide.

TO BE A PLANT: Need to... ●collect____ ●____ it into ____ ●store_____ ●. in a _____ to be ____ around the ____or____ Plants need to get ______ atoms from the _____ ●(ex's of such atoms) ●produce all _____ -(____,___,___,___) Obtaining raw materials ●one ex raw material -leaves = ●other ex raw material -_____=____ exchange and _____ ●other ex raw material -uptake ____ ●other ex raw material -which elements? -uptake Chloroplasts ●_____ membrane ●stroma? it is a ●_____ sacs ●_____ stacks ——Thylakoid membrane contains—- ●______ molecules ●______ ●______ ●____ built up within _____

-collect light energy -transform it into chemical energy -light energy -stable form to be moved around the plant or stored building block, environment -C,H,O,N,P,K,S,Mg -organic molecules needed for growth -carbohydrates, proteins, lipids, nucleic acids sunlight -solar collectors CO2 -stomates = gas exchange and transpiration H2O -from roots Nutrients -N, P, K, S, Mg, Fe... -uptake from roots double stroma- fluid-filled interior ●thylakoid sacs ●grana stacks -Thylakoid membrane contains- ●chlorophyll molecules ●electron transport chain ●ATP synthase ●H+ gradient built up within thylakoid sac

. A considerable amount of sugar in the form of ____ is ____ to make the _____ (see e 3.11c), especially in plant cells that are still growing and maturing. Cellulose, the main ingredient of ____s, is the most ______- and probably on the surface of the planet. Most plants and other photosynthesizers manage to make _____ each day than they ____ to use as ____ and ____ for biosynthesis. They stockpile the ____ by synthesizing ___, _____ some in the ____ themselves and some in storage cells of ___, ___, ____, and ____ . In accounting for the _____ of the _____ produced by ____, let's not forget that most plants lose ___,____,_____, and some- times their ____ to ____, including humans. On a global scale, photosynthesis is responsible for the ____ in our atmosphere. Furthermore, while each chloroplast is ____, their collective ___ is prodigious: Photosynthesis makes an estimated ___ metric tons of carbohydrate per year No chemical process is more important than photosynthesis to the __ of __ on Earth.

. A considerable amount of sugar in the form of glu- cose is linked together to make the polysaccharide cellulose (see e 3.11c), especially in plant cells that are still growing and maturing. Cellulose, the main ingredient of cell walls, is the most abundant organic molecule in the plant- and probably on the surface of the planet. Most plants and other photosynthesizers manage to make more organic material each day than they need to use as respi- ratory fuel and precursors for biosynthesis. They stockpile the extra sugar by synthesizing starch, storing some in the chlo- roplasts themselves and some in storage cells of roots, tubers, seeds, and fruits. In accounting for the consumption of the food molecules produced by photosynthesis, let's not forget that most plants lose leaves, roots, stems, fruits, and some- times their entire bodies to heterotrophs, including humans. On a global scale, photosynthesis is responsible for the c e oxy- gen in our atmosphere. Furthermore, while each chloroplast is minuscule, their collective food production is prodigious: Photosynthesis makes an estimated 150 billion metric tons of carbohydrate per year (a metric ton is 1,000 kg, about 1.1 tons). No chemical process is more important than photosynthesis to the welfare of life on Earth.

A typical mesophyll cell has about ____ chloroplasts, each measuring about 2-4 um by 4-7 um. A chloroplast has an envelope of _____s surrounding a ____ called the ___ . Suspended within the stroma is a third membrane system, made up of _____, which segregates the___ from the ___ In some places, thylakoid sacs are Chlorophyll, the _____, resides in the ___ of the chloroplast The internal ____ of some prokaryotes are also called thylakoid membranes; It is the _____ that drives the synthesis of organic molecules in the chloroplast. In the presence of ___, the green parts of plants produce ___ and ___ from ___ and ____ EQUATION... We use glucose (C,H,O) here to ____but the direct prod- uct of photosynthesis is actually a ___ that can be Water appears on both sides of the equation because ___ molecules are consumed and ___ molecules are newly formed during photosynthesis. , Writing the equation in this form, we can see that the overall chemical change during photosynthesis is the reverse of the one that occurs during cellular respiration. Both of these meta- bolic processes occur in ____s.

30-40, envelope of two membranes, dense fluid, stroma sacs called thylakoids, stroma from the thylakoid space inside these sacs. stacked in columns called grana (singular, granum). green pigment that gives leaves their color thylakoid membranes photosynthetic membranes light energy absorbed by chlorophyll light, organic compounds and oxygen from carbon dioxide and water. 6CO2 + 6 H2O + light energy ——>c6h12o6 + 6O2 simplify the relationship between photosynthesis and respiration, three-carbon sugar that can be used to make glucose 12, 6 plant cell

Remember what it means to be a plant!! Need to produce all ____ for _____ -4 main ●Need to store ____ -in a more ____ -that can be _____ around ____ -saved for a _____ equation?? Light reactions ●Convert ___ to ___ ●ATP.—->____ ●____—->_____ ●What can we do now? How is this helpful? Want to make ____ ●____ Carbon fixation does what to CO2? ——From CO2 —-> glucose —- CO2 has very little _____ -fully ●C6H12O6 contains a _____ -highly ____ ●Synthesis = _____ process -put in —- ●Reduction of ____->_____ proceeds in ____ -each ___ by a ____ -using ___d in ___ and _____ From Light reactions to Calvin cycle ●Calvin cycle -where ●Need ___ of ___ to drive ___ reactions (—- and ——) CALVIN CYCLE: 1.) —— 2.) —- 3.)—- OF ——

Need to produce all organic molecules necessary for growth -carbohydrates, lipids, proteins, nucleic acids ●Need to store chemical energy (ATP) produced from light reactions ●in a more stable form ●that can be moved around plant ●saved for a rainy day 6CO2 + 6H2O + light energy—> C6H12O6 + O2 Light reactions ●Convert solar energy to chemical energy ●ATP to energy ●NADPH to reducing power ●What can we do now? build stuff! Want to make C6H12O6 ●synthesis Carbon fixation does what to CO2? reduces it CO2 has very little chemical energy ●fully oxidized ●C6H12O6 contains a lot of chemical energy ●highly reduced ●Synthesis = endergonic process ●put in a lot of energy ●Reduction of CO2 C6H12O6 proceeds in many small uphill steps ●each catalyzed by a specific enzyme ●using energy stored in ATP & NADPH From Light reactions to Calvin cycle ●chloroplast stroma ●Need products of light reactions to drive synthesis reactions ●ATP ●NADPH CALVIN CYCLE: 1.) Carbon fixation 2.) reduction 3.)Regeneration OF RuBP

CALVIN CYCLE Phase 1: The first phase is______. The Calvin cycle incorpo- rates each ____by attaching it to a ___-____ ____ named _____ (ab- breviated _____). The enzyme that catalyzes this first step is _________, or ____. (This is the most ____ in chloroplasts and is also thought to be the most ____ on ____.) The product of the reaction is a ____ so ____ that it immediately ___ in ____, forming two molecules of ____ Phase 2: _____. Each molecule of _____receives an _____ from ____, be- coming _____Next, a pair of ____ donated from ____ reduces _____, which also ____, becoming ______. Specifi- cally, the electrons from ____ reduce a ___ group on 1,3-bisphosphoglycerate to the __ group of ____, which stores more ___ ___ . G3P is a ______-the same _ sugar formed in __ by the split- ting of glucose. For every ___ molecules of CO2 that enter the cycle, there are ____ molecules of __ formed. But only ____ of this three-carbon sugar can be ___ as a ____ of carbo- hydrate, because the rest are ____. The cycle began with _____. Now there are ___ carbons' worth of carbohydrate in the form of ____. One molecule exits the cycle to be ____ by the _____ cell, but the other ___ molecules must be ___ to __ the ___ molecules of ____. __

Phase 1: Carbon fixation. The Calvin cycle incorpo- rates each CO, molecule, one at a time, by attaching it to a five-carbon sugar named ribulose bisphosphate (ab- breviated RuBP). The enzyme that catalyzes this first step is RuBP carboxylase/oxygenase, or rubisco. (This is the most abundant protein in chloroplasts and is also thought to be the most abundant protein on Earth.) The product of the reaction is a six-carbon intermediate so unstable that it immediately splits in half, forming two molecules of 3-phosphoglycerate (for each CO, fixed). Phase 2: Reduction. Each molecule of 3-phosphoglycerate receives an additional phosphate group from ATP, be- coming 1,3-bisphosphoglycerate. Next, a pair of electrons donated from NADPH reduces 1,3-bisphosphoglycerate, which also loses a phosphate group, becoming G3P. Specifi- cally, the electrons from NADPH reduce a carboyxl group on 1,3-bisphosphoglycerate to the aldehyde group of G3P, which stores more potential energy. G3P is a sugar-the same three-carbon sugar formed in glycolysis by the split- ting of glucose (see Figure 7.9). Notice in Figure 8.17 that for every three molecules of CO, that enter the cycle, there are six molecules of G3P formed. But only one molecule of this three-carbon sugar can be counted as a net gain of carbo- hydrate, because the rest are required to complete the cycle. The cycle began with 15 carbons' worth of carbohydrate in the form of three molecules of the five-carbon sugar RuBP. Now there are 18 carbons' worth of carbohydrate in the form of six molecules of G3P. One molecule exits the cycle to be used by the plant cell, but the other five molecules must be recycled to regenerate the three molecules of RUBP.

Phase 3: Regeneration of the ____ ). In a complex series of reactions, the carbon skeletons of five molecules of ____ are ____ by the last steps of the s of Calvin cycle into ___ molecules of ____. To accomplish this, the cycle spends ____ more ____. The RUBP is now ____ to receive ____ again, and the cycle continues. For the net synthesis of one G3P molecule, the Calvin cycle consumes a total of ____ molecules of ____ and__ __ molecules of ____. The light reactions regenerate the ___ and ____. The G3P spun off from the Calvin cycle becomes the ______(from two molecules of ___) and other ____. Neither the light reactions nor the Calvin cycle alone can make ____,. Photosynthesis is ____ property of the ____which integrates the two stages of photosynthesis. Ever since plants first moved onto land about 475 million years ago, they have been adapting to the problem of ____. Solutions require trade offs. An example is the balance between __ and ___ The ____, required for pho- tosynthesis enters a leaf (and the resulting ____ exits) via ___, the ____ However, ___ are also the main avenues of the ____ ___ of ____ from ____ and may be partially or fully ____ on ___s. This prevents ____, but also ____ , In most plants, initial fixation of carbon occurs via Such plants are called ___ plants because the first or- ganic product of carbon fixation is a ____ C3 plants include im- portant ____ plants such as ___,___,___ns. When their stomata close on hot, dry days, C3 plants produce ____ bc of ⭐️ In addition, rubisco is capable of ___ ___, in place of ___. As ___ becomes scarce and ___ builds up, rubisco ___to the Calvin cycle instead of ___. the product ___, forming a ___ compound that ___ the ___ and is ___n in the cell, releasing ___, ⭐️ The process is called ____ because it occurs in the ___and ____while producing ____, (___). However, unlike normal cell reps, ____ uses ___ rather than generating it. And unlike photosynthesis, photores- piration _____ In fact, photorespiration decreases _______ by siphoning ____al from the Calvin cycle and releasing ____, that would otherwise be ___.

Phase 3: Regeneration of the CO, acceptor (RuBP). In a complex series of reactions, the carbon skeletons of five molecules of G3P are rearranged by the last steps of the s of Calvin cycle into three molecules of RuBP. To accomplish this, the cycle spends three more ATPS. The RUBP is now prepared to receive CO, again, and the cycle continues. For the net synthesis of one G3P molecule, the Calvin cycle consumes a total of nine molecules of ATP and six molecules of NADPH. The light reactions regenerate the ATP and NADPH. The G3P spun off from the Calvin cycle becomes the starting material for metabolic pathways that synthesize other organic compounds, including glucose (from two molecules of G3P) and other carbohydrates. Neither the light reactions nor the Calvin cycle alone can make sugar from CO,. Photosyn- emergent property of the intact chloroplast, which thesis is an integrates the two stages of photosynthesis. Ever since plants first moved onto land about 475 million years ago, they have been adapting to the problem of dehydration. The solutions often involve trade-offs. An example is the balance between photosynthesis and the prevention of excessive water loss from the plant. The CO, required for pho- tosynthesis enters a leaf (and the resulting 0, exits) via stomata, the pores on the leaf surface However, stomata are also the main avenues of the evaporative loss of water from leaves and may be partially or fully closed on hot, dry days. water loss, but it also reduces CO, levels In most plants, initial fixation of carbon occurs via rubisco, the Calvin cycle enzyme that adds CO, to ribulose bisphos- Sa lear phate. Such plants are called C3 plants because the first or- ganic product of carbon fixation is a three-carbon compound, 3-phosphoglycerate (see Figure 8.17). C3 plants include im- portant agricultural plants such as rice, wheat, and soybeans. When their stomata close on hot, dry days, C, plants produce less sugar because the declining level of CO, in the leaf starves the Calvin cycle. In addition, rubisco is capable of binding O, in place of CO. As CO, becomes scarce and O, builds up, rubisco adds O, to the Calvin cycle instead of CO,. The product splits, forming a two-carbon compound that leaves the chloroplast and is broken down in the cell, releasing CO2 The process is called photorespiration because it occurs in the light (photo) and consumes O, while producing CO, (respiration). However, unlike normal cellular respiration, photorespiration uses ATP rather than generating it. And unlike photosynthesis, photores- piration produces no sugar. In fact, photorespiration decreases photosynthetic output by siphoning organic material from the Calvin cycle and releasing CO, that would otherwise be fixed.

Phorespiration is evolutionary ____- a metabolic ____from a much earlier time when the atmosphere had ____ and ____ than it does today. In THE ANCIENT ATMOSPHERE THAT PREVAILED WHEN____ FIRST evolved, the ability of the ____ to bind ____ would have made little difference. The hypothesis suggests that modern rubisco retains some of its ____ for ___ which is now so concentrated in the atmosphere that ____is inevitable. There is also some evidence that _____ may provide protection against ____ products of the _____ that build up when the Cal- vin cycle ____ due to ____. In some plant species, alternate modes of _____ have evolved that minimize _____ and optimize the ____-even in ____,____ climates. The two most impor- tant of these photosynthetic adaptations are ___ and ____ The C4 plants are so named because they carry out a ____ for ____synthesis that first_____ into a ____ compound. When the weather is hot and dry, a C4 plant ____, thus ____r. ____continues to be made, however, through the function of two different types of photosynthetic cells: ___ and ____ An enzyme in the meso- phyll cells has ____ for _____ and can ___ even ____ The resulting_____compound then acts as a _____; it moves into _____ cells, which are packed around the ____of the ____, and releases ___ . Thus, the CO2 concentration in these cells ____for the Calvin cycle to _____ and avoid _____ The C4 pathway is believed to have_____ at least 45 times and is used by several thousand species in at least 19 plant families. Among the C4 plants important to agriculture are ___ and ___< members of the _____

baggage, relic , less O2, more CO2 In THE ANCIENT ATMOSPHERE THAT PREVAILED WHEN RUBISCO FIRST evolved, the ability of the enzymes first active site to bind O2 would have made little difference. The hypothesis suggests that modern rubisco retains some of its chance affinity for O2 which is now so concentrated in the atmosphere that a certain amount of photorespiration is inevitable. There is also some evidence that photorespiration may provide protection against damag- ing products of the light reactions that build up when the Cal- vin cycle slows due to low CO2 In some plant species, alternate modes of carbon fixation have evolved that minimize photorespiration and optimize the 10 Calvin cycle-even in hot, arid climates. The two most impor- tant of these photosynthetic adaptations are C4 photosynthesis and crassulacean acid metabolism (CAM). The C4 plants are so named because they carry out a modi- fied pathway for sugar synthesis that first fixes CO, into a four-carbon compound. When the weather is hot and dry, a C4 plant partially closes its stomata, thus conserving water. Sugar continues to be made, however, through the function of two different types of photosynthetic cells: mesophyll cells and bundle-sheath cells (Figure 8.18a). An enzyme in the meso- phyll cells has a high affinity for CO, and can fix carbon even when the CO, concentration in the leaf is low. The resulting four-carbon compound then acts as a carbon shuttle; it moves into bundle-sheath cells, which are packed around the veins of the leaf, and releases CO2 Thus, the CO2 concentration in these cells remains high enough for the Calvin cycle to make sugars and avoid photorespiration. The C4 pathway is believed to have evolved independently at least 45 times and is used by several thousand species in at least 19 plant families. Among the C4 plants important to agriculture are sugarcane and corn (maize), members of the grass family.

After discussing the general principles of photosynthesis, we'll consider the two stages of photosynthesis: the light reactions, which ______and the Calvin cycle, which uses ______. Photosynthesis converts ___ to _____ The remarkable ability of an organism to _____y and use it to drive the ___ of ____ emerges from _____ in the cell: Photosynthetic en- zymes and other molecules are _____r in a _____, enabling the necessary series of _____s to be carried out efficiently . The process of photosynthesis most likely originated in a group of ____ that had ____ regions of the ____ containing clusters of such molecules. In photosynthetic bacteria that exist today, ____ function similarly to the ____, a ____ organelle Accord- ing to the endosymbiont theory, the original chloroplast was Chloro- plasts are present in a variety of _____ organisms, but here we focus on chloroplasts in ___ . All ____ of a plant, including _____, have chloroplasts, but the ___ are the major sites of photosynthesis in most plants ). Chloroplasts are found mainly in the cells of the _____, the ____ _____enters the leaf, and ___ exits, by way of ____ Water absorbed by the roots is ____ Leaves also use ___ to export _____ to ___ and other ___

capture solar energy and transform it into chemical energy; that chemical energy to make the organic mol- ecules of food light energy to the chemical energy of food harness light energy, synthesis of organic compounds, structural organization grouped together in a biological membrane, chemical reactions bacteria that had infolded regions of the plasma membrane containing clusters of such molecules infolded photosynthetic membranes, internal membranes of the chloroplast, a eukaryotic organelle. a photosynthetic prokaryote that lived inside an ancestor r of eukarvotic cells. photosynthesizing, plants green parts, green stems and unrip- ened fruit, leaves mesophyll, tissue in the interior of the leaf. Carbon dioxide , oxygen, microscopic pores called stomata (singular, stoma; from the Greek, mean- ing "mouth"). delivered to the leaves in veins., veins, sugar to roots and other nonphotosynthetic parts of the plant.

The ____ in plants and other ____ organisms capture ____t energy that has traveled 150 million km from the ___ and convert it to _____ that is This conversion process is called ____ Photosynthesis ___ almost the entire ____directly or indirectly. An organism acquires the ____ it uses for energy and _____s by one of two maior modes: ___ or ___ Autotrophs are "____-_____"; they sustain themselves without . Autotrophs produce _____ from ___ and other They are the ulti- mate sources of ____ for all _____organisms, and for this reason, biologists refer to autotrophs as the Almost all plants are _____; the only nutrients they re- quire are Specifically, plants are _____, organ- isms that Photosynthesis also occurs in ___,___,___ Heterotrophs are unable to _____; they live on ___\ by_____ . Heterotrophs are the biosphere's _____ . This "___-_____g" is most obvious when an animal ____ or ____ Some heterotrophs _____ and ___ on the remains of Most ____ and many types of _____ get their nourishment this way. Almost all heterotrophs, including humans, are completely ______, either directly or indirectly, on ____ for ___ and ____

chloroplasts, photosynthetic, light, sun, chemical energy that is stored in sugar and other organic molecules. photosynthesis nourishes, living world organic compounds, carbon skeleton, autotrophic nutrition or heterotrophic nutrition self-feeders" (auto- means "self, and trophos means "feeder"), eating any- thing derived from other living beings their organic molecules, CO2, inorganic raw materials obtained from the environment. organic compounds, nonautotrophic organisms, producers of the biosphere. autotrophs, water and minerals from the soil(u have ex's) and carbon dioxide from the air photoautotrophs, use light as a source of energy to synthesize organic substances algae, certain other unicellular eukaryotes, and some prokaryotes. make their own food; compounds produced by other organisms (hetero- means "other") consumers ", other-feeding", eats plants or other animals, but heterotrophic nutrition may be more subtle. , decompose and feed on the remains of dead organisms organic litter such as feces and fallen leaves: these types of organisms are known as decomposers. Most fungi and many types of prokaryotes get their nourishment this way. Almost all heterotrophs, including humans, are completely dependent, either directly or indirectly, on photoautotrophs for food-and also for oxygen, a by-product of photosynthesis.

Light reactions ●light-____ reactions ●energy ____ reactions ●convert ____ to _____ ●Calvin cycle ●light-——-reactions ●_____reactions ●uses ____ energy (___,___) to ___ abd ____ Light reactions Electron Transport Chain •like in _____n ●proteins in ______ ●electron acceptors- ex? ●proton ___ -find the ____ membrane! ●______ enzyme ETC of Respiration -Mitochondria transfer -___ and ____ create___ ETC of Photosynthesis Chloroplasts____ ●use electron carrier ____ -creates ___ In photosynthesis, _______.... moves the _____ ●runs the ___ ●____ the ____ ●builds the ____ ●drives the ____ of ____ ●bonds ___ to ___ ●generates the ____ In respiration, what does all those things^^^ PIGMENTS OF PHOTOSYNTHESIS Chlorophylls & other pigments ●embedded in ____ ●arranged in a "_____" -collection of ●____-______n relationship Spectrum Of Light -Shorter wavelength——-> longest -Highest energy —-> lowest GIVE ME THe order of visible then other types of lifht Light: absorption spectra ●Photosynthesis gets energy by _____ ●_______ -absorbs best in ——- wavelengths & least in_____ ●accessory pigments with different ____ absorb _____ -ex's??

dependent... conversion solar energy to chemical energy ATP & NADPH independent sugar building ●uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6 ● like in cellular respiration ●proteins in organelle membrane ●electron acceptors- NADPH ●proton (H+) gradient across inner membrane -find the double membrane! ●ATP synthase enzyme transfer chemical energy from food molecules oxidative phosphorylation and ETC create water transform light energy into chemical energy of ATP NADPH O2 SUNLIGHT ⭐️ moves the electrons ●runs the pump ●pumps the protons ●builds the gradient ●drives the flow of protons through ATP synthase ●bonds Pi to ADP ●generates the ATP ... that evolution built Breakdown of glucose, powered by oxygen ●embedded in thylakoid membrane ●arranged in a "photosystem"- collection of molecules ●structure-function relationship -V I B G Y O R (shortest wavelength, highest energy to longest wavelets and lowest energy) -Gamma, x-ray, UV, visible, IR, microwaves, radio waves ●Photosynthesis gets energy by absorbing wavelengths of light ●chlorophyll a ●absorbs best in red & blue wavelengths & least in green ●accessory pigments with different structures absorb light of different wavelengths ●chlorophyll b, carotenoids, xanthophylls

The excited state, like all _____y states, is ___ . Generally, when isolated pigment molecules ____t, their ____ electrons ____to the _____ in a billionth of a second, releasing their _____ as ____ This is a conversion of In isolation, some pigments, including ____, ____ as well as ___ after ______ As excited electrons fall back to the ground state, An illuminated solution of _____ isolated from ____ will fluoresce in the ____ part of the spectrum and also ____. This is best seen by illuminating with ____, which chlorophyll can also absorb Viewed under visible light, the fluorescence would be Chlorophyll molecules excited by the _____ produce very different results in an ___ than they do in ___ In their native environment of the _____, chlorophyll molecules are organisez along with___ into A photosystem is composed of a The reaction-center complex is an organized association of ____ holding ____ Each light-harvesting complex consists of ___ bound to ____ . The ____ and ____ of pigment molecules enable a photosys- tem to ___ over a ___ and ____ of the spectrum than _____. Together, these light-harvesting complexes act as an When a pigment mol- ecule absorbs a photon, describe how travels The reaction- center complex also contains a molecule capable of ___ and becoming ____

high-energy, unstable absorb light, excited electrons drop back down to the ground-state electron shell in a billionth of a second, releasing their excess energy as heat. light energy to heat energy chlorophyll, emit light as well as heat after absorbing photons photons are given off, an afterglow called fluorescence. chlorophyll, chloroplasts will fluoresce in the red- orange part of the spectrum and also give off heat. ultraviolet light hard to see against the green of the solution. absorption of light en- ergy produce very different results in an intact chloroplast than they do in isolation thylakoid membrane, organized along with other small organic molecules and proteins into complexes called photosystems. reaction-center complex surrounded by several light-harvesting complexes organized association of proteins holding a special pair of chlorophyll a molecules. various pigment molecules (which may include chlorophyll a, chlo- rophyll b, and multiple carotenoids) bound to proteins number and variety of pigment molecules enable a photosys- tem to harvest light over a larger surface area and a larger por- tion of the spectrum than could any single pigment molecule a lone. an- tenna for the reaction-center complex. energy is transferred from pigment molecule to pigment molecule within a light-harvesting com- plex, somewhat like a human "wave" at a sports arena, until it is passed into the reaction-center comple accepting electrons and becoming reduced; this is called the primary electron acceptor. (LOOK AT PIC.. SO PHOTON OF LIGHT COMES IN AND HITS pigment molecules in light harvesting complexes and then enery transfers from pigment to pigment until reach special pair chlorophyll a molecules in reaction center complex and thenprimarh electorn acceptor accepts

All life needs a constant ●Heterotrophs (_____)(_____) -get their energy from "____" -eat food = ●make energy through Autotrophs (___)(____) ●produce ●convert ●build ____ from _____ ●make ____ & synthesize ——- through ____ Heterotrophs -making ____ & _____ molecules from ingesting ____ -glucose plus oxygen —-> Autotrophs -making ____ & _____ molecules from _______ -6CO2 + 6H2O + light energy —->

input of energy Animals)(consumers) eating others other organisms = organic molecules respiration Plants, producers. their own energy (from "self") energy of sunlight organic molecules (CHO) from CO2 energy & synthesize sugars through photosynthesis energy & organic molecules from ingesting organic molecule carbon dioxide + water + ATP (oxidation is C6H12O6 to 6CO2, exerginjc) energy & organic molecules from light energy C6H12O6 + 6O2 (reduction 6CO2 to C6H12O6 is endergonic)

Now let's see how the two photosystems work together in using ____y to generate ___ and ___, the two main products of the light reactions. ___ drives the synthesis of ___ and ____ by ___ the two ____ embedded in the ____ membranes of chloroplasts. The key to this energy transformation is a This is called ____ and it occurs during the ____ of photosynthesis PROCESS: 1.) A photon of light _____ in a ____x of ___, boosting ____l. As this electron falls back to its ground state, an_____. The process continues, with the energy ____ until it___. (It ___ an ____ in this pair of ___ to a ____) 2.)This electron is transferred from the ____to the ___. We can refer to the resulting form of ___, missing an ___, as ____ _ 3.) ⭐️ An enzyme ____ the splitting of a ____ into ____, ___, and an ___atom. The electrons are supplied one by one to the ____, each ____ replacing one transferred to the _____. P680+ is the ____ known; its ____must be ___. This greatly facilitates the __ from the ___ molecule The H* are released into the ____. The oxygen atom immediately ____ with ___ atom generated by the ____, forming ___ 4)Each photoexcited electron passes from the ____r of PS ___ to PS I___ via an ___, the components of which are similar to those of the ___ that functions in cellular_ respira- tion. The ___n between PS II and PS I made up of the ____(__), a _- __, and a protein called __ 5.) The _____l provides energy for the synthesis of ATP. As electrons pass through the _____x, H+ are pumped into the thylakoid space, contributing to the ___t that is then used in __, to be discussed shortly. 6)Meanwhile, light energy has been transferred via ____ to the __x, exciting an __ of the ____ located there. The photoexcited electron is then transferred to __r, cre- ating an ___" in the ___-which we now can call __ In other words, ____ can now act as an ____r, accepting an ___ that reaches the ___ of the ____

light en- ergy to generate ATP and NADPH, the two main products of the light reaction Light drives the synthesis of ATP and NADPH by energizing the two photosystems embedded in the thylakoid membranes of chloroplasts flow of electrons through the photosystems and other molecular components built into the thylakoid membrane. linear electron flow, and it occurs during the light reactions of photosynthesis 1.) A photon of light strikes one of the pigment molecules in a light-harvesting complex of PS II, boosting one of its electrons to a higher energy level. As this electron falls back to its ground state, an electron in a nearby pigment molecule is simultaneously raised to an excited state. The process continues, with the energy being relayed to other pigment molecules until it reaches the P680 pair of chlo- rophyll a molecules in the PS II reaction-center complex. It excites an electron in this pair of chlorophylls to a higher energy state. 2.)This electron is transferred from the excited P680 to the primary electron acceptor. We can refer to the resulting form of P680, missing an electron, as P680*. 3.)An enzyme catalyzes the splitting of a water molecule into two electrons, two hydrogen ions (H*), and an oxy- gen atom. The electrons are supplied one by one to the P680* pair, each electron replacing one transferred to the primary electron acceptor. (P680* is the strongest biolog- oxidizing agent known; its electron "hole" must be filled. This greatly facilitates the transfer of electrons from the split water molecule.) The H* are released into the thylakoid space. The oxygen atom immediately combines with an oxygen atom generated by the splitting of another water molecule, forming O2 O Each photoexcited electron passes from the primary elec- tron acceptor of PS II to PS I via an electron transport chain, the components of which are similar to those of the electron transport chain that functions in cellular respira- tion. The electron transport chain between PS II and PS I made up of the electron carrier plastoquinone (Pq), a cyto- chrome complex, and a protein called plastocyanin (Pc). The exergonic "fall" of electrons to a lower energy level provides energy for the synthesis of ATP. As electrons pass through the cytochrome complex, H* are pumped into the thylakoid space, contributing to the proton gradi- ent that is then used in chemiosmosis, to be discussed shortly. O Meanwhile, light energy has been transferred via light- harvesting complex pigments to the PS I reaction-center complex, exciting an electron of the P700 pair of chloro- phyll a molecules located there. The photoexcited electron is then transferred to PS I's primary electron acceptor, cre- ating an electron "hole" in the P700-which we now can call P700*. In other words, P700* can now act as an electron acceptor, accepting an electron that reaches the bottom of the electron transport chain from PS II.

Two stages of photosyntheis are known as the __ and the ____ The light reactions are the steps of photosynthesis that ____ What happens? -____ is split, providing a source of __ and ____...and giving off ___, as a by-product. -Light absorbed by ____ drives a ____ of the ___ and the ____s from water to an _____, where they are temporarily stored. The electron acceptor ____* is first cousin to ____*, which functions as an electron carrier in cellular respiration; the two molecules differ only by the presence of____ The light reactions use solar energy to The light reactions also generate ____, using ____ to power the addition of a ____ to ____, a process called ____. Thus, light energy is initially _____ in the form of two com- pounds: ___ and ____ NADPH, a source of ___, acts as "_____" that can be passed along to ____, ___ it, while ATP is the _____ of cells. Notice that the light reactions produce no ___; that happens in the second stage of photosynthesis, the ___ The calvin cycle begins by incorporating ___, from the __ into ____ already present in the ___. Carbon fixation:: The Calvin cycle then ___ the fixed carbon to ____ by the __ of _____. The ____ power is provided by ___, which acquired its cargo of electrons in ____. To convert __ to __, the Calvin cycle also requires ____ in the form of ____, which is generated by Thus, it is the Calvin cycle that makes ____, but it can do so only with the help of the ___ and ___ The metabolic steps of the Calvin cycle are sometimes referred to as the ____ or ____t reactions, because _____ ⭐️ ⭐️ . Nevertheless, the Calvin cycle in most plants occurs ___, for only then can ___ In es- sence, the chloroplast uses ____ to make ___ by coor- dinating the __ stages of ___

light reactions (the photo part of photosynthesis) and the Calvin cycle (the synthesis part) con- vert solar energy to chemical energy. Water is split, providing a source of electrons and protons (hydrogen ions, H*) and giving off O2 as a by-product. chlorophyll drives a transfer of the electrons and hydrogen ions from water to an acceptor called NADP* (nicotinamide adenine dinucleotide phosphate), where they are temporarily stored. nadp+ is first cousin to NAD*, which functions as an electron carrier in cellular respiration; the two molecules differ only by the presence of an extra phosphate group NADP* molecule. re duce NADP* to NADPH by adding a pair of electrons along with an H*. ATP, using chemi- osmosis to power the addition of a phosphate group to ADP, a process called photophosphorylation. converted to chemical energy, NADPH and ATP. electrons, acts as "reducing power" that can be passed along to an electron acceptor, reducing it, while ATP is the versatile energy currency of cell, sugar, Calvin cycle CO2, from the air into organic molecules already present in the chloroplast. This initial incorporation of carbon into organic compounds is known as reduces the fixed carbon to carbohydrate by the addition of electrons. The reducing power is provided by NADPH, which acquired its cargo of electrons in the light reactions. CO2 to carbohydrate, chemical energy the form of ATP, which is also generated by the light reac- tions. sugar, NADPH and ATP produced by the light reactions. dark reactions, or light- independent, none of the steps requires light directly during daylight the light reactions provide the NADPH and ATP that the Calvin cycle requires. light energy to make sugar by coor- dinating the two stages of photosynthesis

On global scale, photosynthesis is the most i____ ●each year photosynthesis... -captures —— -synthesizes —- billion tons of —- Heterotrophs are dependent on ____ as ●All the solid material of every plant was built by ____ ●All the solid material of every animal was built from _____ Remember what plants need Photosynthesis- Light reactions -___ from ___ - ____ from ____ Calvin cycle -___ from ___ LOOK AT PIC OF PLANT CELL ——-Controlling water loss from leaves——- On ___ or ___ days, ●stomates____ ●guard cells do what? - gain ___ = ___ -lose ___ = _____ ●adaptation to _____but...creates PROBLEMS! Closed stomates lead to... ●____ from ___ reactions ●CO2 is ___ in the ____ ●causes problems in ____ Inefficiency of RuBisCo: CO2 vs O2 ●RuBisCo in ____ -____enzyme -normally bonds —-to —- -_is the optimal substrate -___ of __ -building ____ it is _____ ⭐️ ⭐️ when___concentration is high ●RuBisCo bonds ___ to ____ ●___ is a ____ substrate!! ●___ of ____ now!' ●_____ -it is _____ ⭐️

On global scale, photosynthesis is the most important process for the continuation of life on Earth ●each year photosynthesis... ●captures 121 billion tons of CO2 ●synthesizes 160 billion tons of carbohydrate heterotrophs are dependent on plants as food source for fuel & raw materials ●All the solid material of every plant was built by sunlight out of thin air ●All the solid material of every animal was built from plant material Remember what plants need Photosynthesis- Light reactions -light from sun - water from ground Calvin cycle -co2 from air LOOK AT PIC OF PLANT CELL Controlling water loss from leaves Hot or dry days ●stomates close to conserve water ●guard cells-gain H2O = stomates open, lose H2O = stomates close ●adaptation to living on land, but... creates PROBLEMS! Closed stomates lead to... ●O2 build up from light reactions ●CO2 is depleted in Calvin cycle ●causes problems in Calvin Cycle Inefficiency of RuBisCo: CO2 vs O2 ●RuBisCo in Calvin cycle ●carbon fixation enzyme ●normally bonds C to RuBP ●CO2 is the optimal substrate ●reduction of RuBP ●building sugars photosynthesis ⭐️ ●when O2 concentration is high ●RuBisCo bonds O to RuBP ●O2 is a competitive substrate ●oxidation of RuBP ●breakdown sugars -photorespiration ⭐️ Calvin cycle when CO2 is abundant (C3 plants) LOOK PHOTOS calvin cycle when O2 abundant...to mitochondria.. lost as co2 without making atp (photorespiration)

The pair of chlorophyll a molecules in the reaction-center complex are special because ____environment-their ____ and the other molecules with _____-enables them to ____ from ____ not only to ____ one of their ____ to a _____ but also to ____ it to a ____-the ______ The ____-powered ____ of an _____ from the ____ to the _____ is one of the first steps of the light reactions. As soon as the chlorophyll electron is excited to a higher energy level, isolated chlorophyll fluoresces because there is no ___, so electrons ____ In the structured environment of a chloroplast, however, an ____ is readily available, and the _____ represented by the ___ is not dissipated as__ and ___ Thus, each photosystem-a _____ surrounded by _____,functions in the ____ as a unit. It converts __ to ___, which ultimately The ____ membrane is populated by ___ that cooperate in the ___ of ____. They are called __ and ___ (They were named in order of their discovery, but photosystem II Each has a characteristic _____-a particular kind of _____r next to a special pair of ____s associated with specific ____ . The reaction-center chlorophyll a of photosystem II is known as ___ because this pigment is best at __ light having a wavelength of ___ _nm (in the ___ part of the spectrum). The chlorophyll a at the reaction-center complex of photosystem I is called P700 because it most effectively ___ light of wavelength ___ nm (in the ___ part of the spectrum). These two pigments, ___ and ____, are nearly _____ However, their association with different ___ in the ___ accounts for

their molecular environment-their location and the other molecules with which they are associated-enables them to use the energy from light not only to boost one of their electrons to a higher energy level, but also to transfer it to a different molecule-the primary electron acceptor. solar-powered transfer of an electron from the reaction-center chlorophyll a pair to the primary electron ac- ceptor is one of the first steps of the light reactions the primary electron acceptor captures it; this is a redox reac- tion. electron acceptor, of photoexcited chlorophyll drop right back to the ground state. electron acceptor is readily available, and the potential en- ergy represented by the excited electron is not dissipated as light and heat reaction-center complex surrounded by light-harvesting complexes-functions in the chloroplast as a unit. It converts light energy to chemical energy, which will ultimately be used for the synthesis of sugar. thylakoid membrane is populated by two types of photosystems that cooperate in the light reactions of pho- tosynthesis. They are called photosystem II (PS II) and photosystem I (PS I). functions first in the light reac- tions reaction-center complex-a particular kind of primary electron acceptor next to a special pair of chlorophyll a molecules associated with specific pro- teins. P680 because this pigment is best at absorbing light having a wavelength of 680 nm (in the red part of the spectrum P700 because it most effectively absorbs light of wavelength 700 nm (in the far-red part of the spectrum). P680 and P700, are nearly identical chlorophyll a molecules. However, their association with different proteins in the thylakoid membrane affects the electron distribution in the two pigments and accounts for the slight differences in their light-absorbing properties

-⭐️ 2 photosystems in —— membrane- ⭐️ ●they are collections of_____ ●act as ____ PHOTOSYSTEM II ●type ●____ = absorbs ___ Photosystem I ●type ●___ = absorbs ___ ETC uses _____ to produce___ and ____ and then go to.. ●PS II _____ -excited ____ passes from ____ to _____ -need to ____in ___ -enzyme extracts ___ and _____ WHATS THUS DO??? ●____ ●___ combines with ___ ●___ released to ●and we ____! Experimental evidence ●Where did the O2 come from? -radioactive ___ = ___ EXP 1: EXP 2: Proved O2 came from _____! NONCYCLIC PHOSPHORYLATION -Light reactions ____ electrons in ___ ●___generates energy as ___ ●____ generates ___as ____ Cyclic Phosphorylation If PS I can't _____, it ____, but no ____ ●coordinates ____s to ____ ●Calvin cycle uses more ___ than ___ EQUATION:

thylakoid chlorophyll molecules ●act as light-gathering molecules Photosystem II ●chlorophyll a ●P680 = absorbs 680nm wavelength red light ●Photosystem I ●chlorophyll b ●P700 = absorbs 700nm wavelength red light ETC uses light energy to produce ATP & NADPH, go to Calvin cycle ●PS II absorbs light -excited electron passes from chlorophyll to "primary electron acceptor" -need to replace electron in chlorophyll -enzyme extracts electrons from H2O & supplies them to chlorophyll ●splits H2O ●O combines with another O to form O2 ●O2 released to atmosphere ●and we breathe easier! -radioactive tracer = O18 EXP 1: 6CO2 + 6H2O + light energy —>C6H12O6 + 6O2 EXP 2: 6CO2+6H2O + light energy—->C6H12O6+ 6O2 Proved O2 came from H2O not CO2 = plants split H2O! -Light reactions elevate electrons in 2 steps (PS II & PS I) ●PS II generates energy as ATP ●PS I generates reducing power as NADPH If PS I can't pass electron to NADP...it cycles back to PS II & makes more ATP, but no NADPH ●coordinates light reactions to Calvin cycle ●Calvin cycle uses more ATP than NADPH 18 ATP + 12 NADPH —> 1C6H12O6

The _____ are the sites of the light reactions, while the Calvin cycle occurs in the ____. On the outside of the thylakoids, molecules of ____ and ____ pick up ____ and ____, respec- tively, and ___ and ____ are then released to the ____, where they play crucial roles in the ___ The light reactions convert ____ to the ____ of ___ and ____ Chloroplasts are chemical factories powered by the ___. Their thylakoids do what?? Liight is a form of energy known as ____ energy, also called ____ Electromagnetic energy travels in ____ analogous to those created by drop- ping a pebble into a pond. Electromagnetic waves, however, are disturbances of _____ rather than disturbances of a material medium such as water. ____is called the wavelength. This entire range of radiation is known as the ____ ). The seg- ment most important to life is the narrow band from about ___ nm to ___ nm in wavelength. This radiation is known as ___ because it can be detected as ____ by the ____ The model of light as waves explains many of light's proper- ties, but in certain respects light behaves as though it Photons are not tangible objects, but they act like objects in that each of them has a _____ The amount of energy is ____ related to the wavelength of the light: The shorter the wave- length, the _____ Thus, a photon of violet light packs nearly ___ as much . Although the sun radiates the ____ of electro- magnetic energy, the atmosphere acts like a ____,allowing ___ while screening out ____

thylakoids of the chloroplast, stroma NADP* and ADP pick up electrons and phosphate, respec- tively, and NADPH and ATP are then released to the stroma, where they play crucial roles in the Calvin cycle. solar energy to the chemical energy of ATP and NADPH sun, transform light energy into the chemical energy of ATP and NADPH electromagnetic, electromagnetic radiation. rhythmic waves, electric and magnetic fields The distance between the crests of electromagnetic waves electromagnetic spectrum 380, 750 visible light various colors by the human eye consists of discrete particles, called photons. each of them has a fixed quantity of energy inversely greater the energy of each photon of that light twice as much en- ergy as a photon of red light (see Figure 8.6) full spectrum selective window, allowing visible light to pass through while screening out a substantial fraction of other radiation.

The proton (_____) or ____, across the ____ membrane is substantial. When chloroplasts in an experimental setting are illuminated, the pH in the ____ drops to about __ (the ____ ____), and the ___ in the _____ to about ___ (the _____ ____). This gradient of three pH units corresponds to a ___ difference in H+ concentration. If the lights are turned off, the _____t is ___, but it can quickly be restored by ___ the ___ ____ ___. Experiments such as this provided strong evidence in support of the ____ model. Each of the molecules and molecular complexes in the figure is _____ in ____ . Notice that NADPH, like ATP, is produced on the ____ facing the ___, where the ____ take place. Let's summarize the light reactions. Electron ___ pushes electrons from ___, where they are at a_____ ultimately to ___, where they are stored at a ______. The ____ electron flow also ____. Thus, the equipment of the ____ converts ___ to ___stored in ___ and ____. _ is a by-product.) Let's now see how the Calvin cycle uses the _____ of the _____ to synthe- size _ from __, The Calvin cycle uses the ___ of ___ and ___ to ____ to ___ The Calvin cycle is similar to the citric acid cycle in that a __ material is _ after some molecules __ and others ____ . However, the citric acid cycle is ____, ___ acetyl CoA and using the energy to synthesize ATP, while the Calvin cycle is ____,, building ____ from ____ and ___ energy.

(H+) or pH gradient across the thylakoids membrane is substantial When chloroplasts in an experimental setting are illuminated, the pH in the thylakoid space drops to about 5 (the H* concentration increases), and the pH in the stroma increases to about 8 (the H* concentra- tion decreases). This gradient of three pH units corresponds to a thousandfold difference in H+ concentration. If the lights are turned off, the pH gradient is abolished, but it can quickly be restored by turning the lights back on. Experiments such as this provided strong evidence in support of the chemios- motic model. Each of the molecules and molecular complexes in the figure is present in numerous copies in each thylakoid. Notice that NADPH, like ATP, is produced on the side of the membrane facing the stroma, where the Calvin cycle reactions take place. Let's summarize the light reactions. Electron flow pushes electrons from water, where they are at a low state of potential energy, ultimately to NADPH, where they are stored at a high state of potential energy. The light-driven electron flow also generates ATP. Thus, the equipment of the thylakoid mem- brane converts light energy to chemical energy stored in ATP and NADPH. Oxygen Let's now see how the Calvin cycle uses the products of the light reactions to synthe- size sugar from CO2, The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar The Calvin cycle is similar to the citric acid cycle in that a starting material is regenerated after some molecules enter and others exit the cycle. However, the citric acid cycle is catabolic, oxidizing acetyl CoA and using the energy to synthesize ATP, while the Calvin cycle is anabolic, building carbohydrates from smaller molecules and consuming energy. Carbon enters the Calvin cycle in CO, and leaves in sugar. The cycle spends ATP as an energy source and consumes NADPH as reducing power for adding high-energy electrons to make sugar. As mentioned in Concept 8.1, the carbohydrate produced directly from the Calvin cycle is not glucose. It is actually a three-carbon sugar named glyceraldehyde 3-phosphate (G3P). For net synthesis of one molecule of G3P, the cycle must take place three times, fixing three molecules of CO,-one per turn of the cycle. (Recall that the term carbon fixation refers to the initial incorporation of CO, into organic material.) As we trace the steps of the Calvin cycle, keep in mind that we are following three molecules of CO, through the reactions.

Glyceraldehyde-3-P ●the ●energy rich ____ ●"______s" ●G3P is an important ____ ●G3P —->____ —->____ lipids —->____, ____, ____ amino acids —->___ nucleic acids —->____, _____ RUBISCO Enzyme which ____ ●full name? ●the most ___ in the ____! ●it makes ____ out of ____! ●definitely the most____ The accounting is complicated ●3 turns of Calvin cycle = ____ ●How many CO2 form how many G3P? ●6 turns of Calvin cycle = ______ ●How many CO2 form how many.... OVERALL NET EQ: ●any ATP left over from light reactions will be Photosynthesis summary ●Light reactions ●produced —- ●produced —— ●consumed —- ●produced — as byproduct ●Calvin cycle ●consumed —- ●produced —- ●regenerated —- ●regenerated —— LIGHT REACTIONS ARE _____ REACTIONS _produces ____ ●produces ____ ●releases ___ as a waste product EQ CALVIN CYCLE IS —— REACTION -builds —- ●uses —-&—— ●recycles —&&— ●back to make more —&— EQ

Glyceraldehyde-3-P ●end product of Calvin cycle ●energy rich 3 carbon sugar ●"C3 photosynthesis" ●G3P is an important intermediate ●G3P —->glucose —->carbohydrates lipids —->phospholipids, fats, waxes amino acids —->proteins nucleic acids —->DNA, RNA RUBISCO Enzyme which fixes carbon from air ●ribulose bisphosphate carboxylase ●the most important enzyme in the world! ●it makes life out of air! ●definitely the most abundant enzyme The accounting is complicated ●3 turns of Calvin cycle = 1 G3P ●3 CO2 —->1 G3P (3C) ●6 turns of Calvin cycle = 1 C6H12O6 (6C) ●6 CO2 —->1 C6H12O6 (6C) ●18 ATP + 12 NADPH —->1 C6H12O6 ●any ATP left over from light reactions will be used elsewhere by the cell Photosynthesis summary ●Light reactions ●produced ATP ●produced NADPH ●consumed H2O ●produced O2 as byproduct ●Calvin cycle ●consumed CO2 ●produced G3P (sugar) ●regenerated ADP ●regenerated NADP LIGHT REACTIONS ARE ENERY BUILDING REACTIONS produces ATP ●produces NADPH ●releases O2 as a waste product H2O+ light enery —>ATP + NADPH +O2 CALVIN CYCLE IS SUGAR BUILDING REACTION builds sugars ●uses ATP & NADPH ●recycles ADP & NADP ●back to make more ATP & NADPH CO2 + H2O + light energy —-> C6H12O6+ O2

Impact of Photorespiration ●____ of ___ ●short circuit of ____ ●loss of __ to ____ -can lose __% of ●reduces production of photosynthesis -no ____ produced -no ____) produced ●if photorespiration could be ____, plant would become __% ___ -strong _____to evolve ____ systems Reducing photorespiration ●Separate _____ from _____ C4 plants ●PHYSICALLY _____ from ___ -different cells to ____ vs. where ____ -store ___ in ____ ●different —- to capture —- (____) What is it? -it is _____ -it has CAM plants ●separate ____ from ____ by ___ OF ___ ●fix carbon ____ -store ____ in ___ ●perform _____ during ___ C4 plants ●A better way to ____ ●1st step before ____, fox -store as ____ ●adaptation to __f,____ -have to _____ a lot -different ____ ●exs ——C4 leaf anatomy—— _____ enzyme ●higher attraction for — than — ●better than —- ●fixes —- in —- compounds ●regenerates —- in — for —- ●keeping —- away from ——

Impact of Photorespiration ●Oxidation of RuBP ●short circuit of Calvin cycle ●loss of carbons to CO2 ●can lose 50% of carbons fixed by Calvin cycle ●reduces production of photosynthesis ●no ATP (energy) produced ●no C6H12O6 (food) produced ●if photorespiration could be reduced, plant would become 50% more efficient ●strong selection pressure to evolve alternative carbon fixation systems Reducing photorespiration ●Separate carbon fixation from Calvin cycle C4 plants ●PHYSICALLY separate carbon fixation from Calvin cycle ●different cells to fix carbon vs. where Calvin cycle occurs ●store carbon in 4C compounds ●different enzyme to capture CO2 (fix carbon) ●PEP carboxylase ●different leaf structure CAM plants ●separate carbon fixation from Calvin cycle by TIME OF DAY ●fix carbon during night ●store carbon in 4C compounds ●perform Calvin cycle during day C4 plants ●A better way to capture CO2 ●1st step before Calvin cycle, fix carbon with enzyme PEP carboxylase ●store as 4C compound ●adaptation to hot, dry climates -have to close stomates a lot -different leaf anatomy ●sugar cane, corn, other grasses... C4 leaf anatomy PEP carboxylase enzyme ●higher attraction for CO2 than O2 ●better than RuBisCo ●fixes CO2 in 4C compounds ●regenerates CO2 in inner cells for RuBisCo ●keeping O2 away from RuBisCo

the action spectrum for photosynthesis is much ____ than the ____ of _____ The absorption spectrum of chlorophyll a alone _____ the ____ of This is partly because _____ with different _____also present in chloroplasts-including ____ and ____-broaden the spectrum of colors that can be used for photosynthesis. Figure 8.10 shows the structure of chlorophyll a compared with that of chlorophyll b. A slight_____between them is enough to cause the ____ to As a result, chlorophyll a appears _____ and chlorophyll b ____under visible light. Other accessory pigments include ____— what are they?? Carotenoids may ___ the sprectrum of ___ that However, a more important function of at least some ca- rotenoids seems to be ____ : These compounds ____ and ____ excessive ____y that would otherwise damage ____ or interact with ___, forming ____s that are dangerous to the cell. Interestingly, carotenoids similar to the _____ have a ____role in the _____ (____, known for aiding ____n, are rich in carotenoids.) What exactly happens when chlorophyll and other pigments absorb light? When a molecule absorbs a ____ of light, one of the molecule's ____ is ____ to an electron shell where it has _____y When the electron is in its normal shell, the ___ molecule is said to be in its Absorption of a photon ____ an electron to a ____, and the pigment molecule is then said to be _____ The only photons absorbed are those whose ___ between ___ and ____e, and this ___varies from one ___ to another Thus, a particular compound absorbs ____, which is why!!!!!!! Once absorption of a photon ____ from ___ to ___\, the electron _____

Notice by comparing Figure 8.9a and 8.9b that the action spectrum for photosynthesis is much broader than the ab- sorption spectrum of chlorophyll a. underestimates the effectiveness of certain wavelengths in driving photosynthesis. accessory pigments with different absorption spectra also present in chloroplasts-including chlorophyll b and carotenoids-broaden the spectrum of colors that can be used for photosynthesis. struc- tural difference two pigments to absorb at slightly different wavelengths in the red and blue parts of the spectrum blue green, olive green carotenoids, hydrocarbons that are various shades of yellow and orange be- cause they absorb violet and blue-green light broaden the spectrum of colors that can drive photosynthesis. photoprotection absorb and dissipate excessive light energy that would otherwise damage chloro- phyll or interact with oxygen, forming reactive oxidative mol- ecules that are dangerous to the cell. Interestingly, carotenoids similar to the photoprotective ones in chloroplasts have a pho- toprotective role in the human eye. Carrots, known for aiding night vision, are rich in carotenoids.) The colors corresponding to the absorbed wave- lengths disappear from the spectrum of the transmitted and reflected light, but energy cannot disappear. photon, molecule's electrons is elevated to an electron shell where it has more potential energy w when the electron is in its normal shell, the pigment molecule is said to be in its ground state. boosts an electron to a higher-energy electron shell, and the pigment molecule is then said to be in an excited state energy is exactly equal to the energy difference between the ground state and an excited state, and this energy difference varies from one kind of molecule to another. T only photons corresponding to specific wavelengths, which is why each pigment has a unique absorption spectrum. raises an electron from the ground state to an excited state, the electron cannot stay there long.

7)Photoexcited electrons are passed in a series of ___ re- actions from the ____ of ___ down a ____ through the protein ____ (__). (This chain does not ___ AND DOEDNT__!!!!!!!!!!!!) 8)The enzyme ____ catalyzes the transfer of electrond from ___ to ____. Two ___ are required for its ___ to ___. This molecule is at a ___than water, so its electrons are _____. This pro- cess also ___ an ___from the stroma. : The light reactions use ____ to generate ___ and ___, which provide ____ and ___ power, respectively, to the _____ of the ___ cycle. chemiosmosis, Chloroplasts and mitochondria generate ____ by An _____ chain assembled in a ____ pumps _____as electrons are ___ a series of ____ that are progressively more _____. Thus, electron transport chains transform ___ to ____, ____ energy stored in the form of ____ An ____ in the same membrane couples the ____ ions ____ to the ____ of _, forming ____. Some of the electron carriers, including the ____-containing proteins called ____, are very similar in ____ and ___. ⭐️⭐️The _____ of the two organelles are also quite similar. But there are noteworthy differences between ___ in chloroplasts and __ ___ in mitochondria. Both work by way of ___, but in chloroplasts, the _____dropped down the transport chain come from __, whereas in mitochondria, they are extracted from _____). Chloroplasts do not need _____ to make ATP; their ____ do what?" In other words, mito- chondria use ____ to transfer ___ energy from ___ to ___, whereas chloroplasts use it to trans- form ____ into _____. Although the spatial organization of chemiosmosis differs slightly _between chloroplasts and mitochondria, it is easy to see similarities in the two The inner membrane of the mitochondrion __s from the __ out to the ___, which then serves as a reservoir of ____. ____ The _____ ___ of the chloroplast ___ from the __ into the ___), which functions as the __ reservoir. if you imagine the ____ of ____ pinching off from the inner membrane, this may help you see how the ___ and the __ space are comparable spaces in the two organelles, while the ____ ____ is analogous to the ____ of the chloroplast. In the mito- chondrion, protons..... In the chloroplast, ___ is syn- thesized as the _____ diffuse from the ____ ___ back to the ___ through ____, whose catalytic ___ are on the stroma side of the membranes . Thus, ATP forms in the ____, where it is used to ___ ___ ___during the ____

O Photoexcited electrons are passed in a series of redox re- actions from the primary electron acceptor of PS I down a second electron transport chain through the protein ferredoxin (Fd). (This chain does not create a proton gradient and thus does not produce ATP.) The enzyme NADP* reductase catalyzes the transfer of electrons from Fd to NADP*. Two electrons are required for its reduction to NADPH. This molecule is at a higher energy level than water, so its electrons are more readily available for the reactions of the Calvin cycle. This pro- cess also removes an H* from the stroma. solar power to generate ATP and NADPH, which provide chemical energy and reducing power, respectively, to the carbohydrate-synthesizing reactions of the Calvin cycle. the process that uses membranes to couple redox reactions to ATP production. ATP by the same basic mechanism: chemiosmosi electron transport chain assembled in a membrane pumps protons (H*) across the membrane as electrons are passed through a series of carriers that are progressively more electronegative. Thus, electron transport chains transform redox energy to a proton-motive force, potential energy stored in the form of an H* gradient across a membrane. An ATP synthase com- plex in the same membrane couples the diffusion of hydrogen ions down their gradient to the phosphorylation of ADP, forming ATP. Some of the electron carriers, including the iron-containing proteins called cytochromes, are very similar in chloroplasts and mitochondria. The ATP synthase com- plexes of the two organelles are also quite similar. But there are noteworthy differences between photophosphorylation in chloroplasts and oxidative phosphorylation in mitochondria. Both work by way of chemiosmosis, but in chloroplasts, the high-energy electrons dropped down the transport chain come from water, whereas in mitochondria, they are extracted from organic molecules (which are thus oxidized). Chloroplasts do not need molecules from food to make ATP; their photosys- tems capture light energy and use it to drive the electrons from water to the top of the transport chain. In other words, mito- chondria use chemiosmosis to transfer chemical energy from food molecules to ATP, whereas chloroplasts use it to trans- form light energy into chemical energy in ATP. Although the spatial organization of chemiosmosis differs slightly between chloroplasts and mitochondria, it is easy to see similarities in the two (Figure 8.15). pumps protons from the mitochondrial matrix out to the intermembrane space, which then serves as a reservoir of hydrogen ions thylakoid membrane of the chloroplast pumps protons from the stroma into the thylakoid space (interior of the thylakoid), which functions as the H* reservoir if you imagine the cristae of mitochondria pinching off from the inner membrane, this may help you see how the thylakoid space and the intermembrane space are comparable spaces in the two organelles, while the mitochondrial matrix is analogous to the stroma of the chloroplast. In the mito- chondrion, protons diffuse down their concentration gradient from the intermembrane space through ATP synthase to the matrix, driving ATP synthesis. In the chloroplast, ATP is syn- thesized as the hydrogen ions diffuse from the thylakoid space back to the stroma through ATP synthase complexes, whose catalytic knobs are on the stroma side of the membranes . Thus, ATP forms in the stroma, where it is used to help drive sugar synthesis during the Calvin cycle.

One of the first clues to the mechanism of photosynthesis came from the discovery that the . The chloroplast splits __ into ___ and ___ Before this discovery, the prevailing hypothesis was that photosynthesis Van Niel was investigating photosynthesis in ___ that make their carbohydrate from ___, but do not release ___ He concluded that, at least in these bacteria, ____ is NOT One group of bacteria used ___ rather than water for photosynthesis, forming ____ of ___ as a waste product (these globules are visible in Figure 8.2e). van Niel hypothesized that plants split ____ as a __ of ___ from ___,, releasing ___ as a by-product. Nearly 20 years later, scientists confirmed van Niel's hy- pothesis by using ____, a heavy isotope, as a tracer to ____n atoms during photosynthesis. um kind of explain exp 1 and 2.. don't NEED to tho A significant result of the shuffling of atoms during pho- tosynthesis is the ___ and incorporation into ___r. The waste product of photosynthesis, ___, is ____ to the ___ Let's briefly compare photosynthesis with cellular respiration. Both processes involve __ reactions. During cellular respi- ration, energy is ___ from __ when electrons associated with ____ are transported by ___ ___, forming ___ as by product. . The electrons ___ energy as they "__ ___" the ___ towards ____n, and the mitochondrion ___ that energy to ____ Photosynthesis ____ of electron flow. ____ is split, and electrons are ____ along with ____ from the water to ____, __ it to _____. Because the electrons increase in ___ as they move from __ to ____,this process ___ energy-in other words, is ____ 🌟 . This energy boost is provided by ___.

O2 given off by plants is derived from H2O and not from CO2 water into hydrogen and oxygen. split carbon dioxide and then added water to carbon. This hypothesis predicted that the O2 released during photosynthesis came from CO2. This idea was challenged in the 1930s by C. B. van Niel, of Stanford University. bacteria, CO2, O2 CO2 is not split into carbon and oxygen. hydrogen sul- fide (H,S), yellow globules, sulfur H2O, source of electrons from hydrogen atoms, O2 oxygen-18 (O), follow the fate of oxygen atoms during photosynthesis The experiments showed that the O2, from plants was labeled with 18O only if water was the source of the tracer (experiment 1). If the "18O was introduced to the plant in the form of CO2 the label did not turn up in the released O2 (experiment 2). extraction of hydrogen from water and its incorporation into sugar O2, released to the atmosphere. redox released from sugar, hydrogen, carriers to oxygen, forming water as a by-products lose potential, fall" down the electron transport chain toward electronegative oxygen, harnesses, synthesize ATP reverses the direction Water, transferred along with hydrogen ions from the water to carbon dioxide, reducing it to suga potential energy as they move from water to sugar, requires, endergonic, light

The en- ergy that enters the chloroplasts as ____ becomes ____ as ____ in ___ As for the fates of photosynthetic products, enzymes in the ____ and ____ convert the ____ made in the Calvin cycle to many other ___ compounds. In fact, the ___ made in the chloroplasts supplies the entire plant with _____ and ____ for the ___ of all the major ____ of plant cells. About ___% of the or- ganic material made by photosynthesis is ____ as ____ for ____ in plant cell ____. ____ cells are the only autotrophic parts of the plant. Other cells depend on _____ exported from leaves via ____ In most plants, carbohydrate is _____ out of the ____ to the rest of the plant as ____, ____.. After arriving at ____ cells, the sucrose ____ for ____ and many ____ that synthesize ___,____,__

The en- ergy that enters the chloroplasts as sunlight becomes stored as chemical energy in organic compounds. . As for the fates of photosynthetic products, enzymes in the chloroplast and cytosol convert the G3P made in the Calvin cycle to many other organic compounds. In fact, the sugar made in the chloroplasts supplies the entire plant with chemi- cal energy and carbon skeletons for the synthesis of all the major organic molecules of plant cells. About 50% of the or- ganic material made by photosynthesis is consumed as fuel for cellular respiration in plant cell mitochondria. Green cells are the only autotrophic parts of the plant. Other cells depend on organic molecules exported from leaves via veins (see Figure 8.19, top). In most plants, carbohydrate transported out of the leaves to the rest of the plant as sucrose, disaccharide. After arriving at nonphotosynthetic cells, the sucrose provides raw material for cellular respiration and many anabolic pathways that synthesize proteins, lipids, and other products.

. The part of the spec- trum we can see-____-is also the radiation that _____ Photosynthetic Pigments: The Light _____ When light meets matter, it may be ___,____,____ Substances that absorb ___ light are known as ____ . Different pigments absorb ____, and the ______ that are _____ If a pigment is illuminated with white light, the color we see is the color We see green when we look at a leaf because ______ The ability of a pigment to absorb various _____ can be measured with an instrument called a _____. This machine directs _____ of _____s through a ____ of the _____ and measures the _____ A graph plotting a pigment's _____versus _____ is called an absorption spectrum The absorption spectra of chloroplast pigments provide _____ to the _____s of ____for driving _____, since light can perform work in chloroplasts only if it___ three types of pigments in chloroplasts: chlorophyll a, the key____,chlorophyll b, the _____ ,and a separate group of ____ called ____ The spectrum of chlorophyll a suggests that ____ and ____ light work best for photosynthesis, since they are ____, while ___ is least effective This is confirmed by an ____ for photosynthesis, which profiles the ___ of différent ______ An action spectrum is prepared by _____s and then plotting ___ against some measure of ____ such as ___ consumption or ___release.

visible light-is also the radiation that drives photosynthesis. Photosynthetic Pigments: The Light Receptors reflected, transmitted, or absorbed. visible , pig- ments light of different wavelengths, and the wavelengths that are absorbed disappear. most reflected or transmitted by the pigment. (If a pigment absorbs all wavelengths, it appears black.) chlorophyll absorbs violet-blue and red light while transmitting and reflecting green light absorb various wavelengths of light can be measured with an instrument called a spectrophotometer. This machine directs beams of light of different wavelengths through a solution of the pigment and measures the fraction of the light transmitted at each wavelength light absorption vs wavelength the relative effectiveness of different wavelengths for driving photosynthesis, since light can perform work in chloroplasts only if it is absorbed. key light-capturing pigment that partici- pates directly in the light reactions; the accessory pigment, accessory pigments called carotenoids. violet-blue and red light work best for photosynthesis, since they are absorbed, while green is the least effective color. action spectrum illuminating chloroplasts with light of different colors, wavelength against some measure of photosynthetic rate, such as CO2consumption or O2release.