chapter 8 notes over photosynthesis the way I will present these notes is with the understanding that you have watched learned hopefully understand chapter 7 Notes over cell respiration photosynthesis is essentially the opposite or reverse of aerobic cell respiration so the better you understand that process the easier this is if you are still a bit confused on cell respiration I would study that up a little bit before you do these the previous slide is a a little animated video about the anatomy of a leaf as always I highly recommend watching the embedded videos especially since um the Blended class missed the cell lab some things about leaves we got to see in there so it would be good for you to watch that in a leaf the Chlor plast the organel that does photosynthesis um is very prevalent in the cells on the top layer of a leaf where sun is hitting them you won't be specifically tested over the anatomy of a leaf for this class but I do think it's relevant and important to know so continuing on related to which you will be tested over autot tropes and heterotrofos autotop Auto meaning automatic on its own tro refers to food means the organism makes its own food there are different types of autot Tres the two major types on Earth that we have and know of are what we call photo autot troes so they use light photo meaning light um specifically sunlight although we can use artificial light when we want to grow plants as well um to make their own food namely sugars this there are procaryotes that do it cob bacteria it's a type of bacterial in the domain bacteria um it's a ancient organism one of the earlier life forms that is actually responsible for putting oxygen the amount of oxygen I should say in our atmosphere algae most algae that we think of are really really single celled ukar that often live together colonially so they can kind of be stringy or appear like a multicellular organism and then of course plants and then we have chemotrophs or sometimes chemo aotrs and these are pretty much exclusively procaryotes just trying I don't not currently aware of any ukar but we could have found some organisms since I last followed this these are procaryotes that take chemical energy and use that to make sugars make their food um these are like inorganic compounds uh the most famous being what we call these thermophilic bacteria that live deep in the ocean around hydrothermal vents where hydrogen sulfide is spewing out in the water and they use water and that hydrogen sulfide um and are able and some other things in there and are able to make glucose and a reaction similar to photosynthesis but they're not using light for the energy they're kind of using heat in this chemical energy there are other examples but the the bacteria and the around the hydrothermal vents is some of the most um interesting and wellknown so those tend to happen in places where there is no sunlight um and the organisms have evolved other ways of making sugars the opposite of an autot TR is our hetero tro hetero meaning opposite or outwards or other tro being food so heterotrophs have to obtain their food from their environment they do not make it internally they do this by consuming material it can be fungi which secrete digestive enzymes to break down things around them and absorb those nutrients it could be animals who engulf for the most part take in in some way the food they're eating there are other single celled ukar or protest remember single cell ukar that are also heterotrophy so this is why we call single cell ukots protest but there is a huge evolutionary difference between Proteus that are autotrophic like algae which most of them are closer related to plants and really the ancestor to plants and then there are heterotrophic protest that are singal side ukari that are heterotrophic that are typically more related to animals or or fungi and um some of which are related to the ancestors of animals and fungi um so they get their food from their environment number of bacteria right say most bacteria and that's kind of that's a generic term there ARA um bacteria and ARA both the protest um many most are heterotrophs some thing I want to comment on here that students often get confused about or misunder understand autot tropes make their own sugars but they still do glycolysis and potentially cell respiration many doing aerobic cell respiration some may do uh an anob cell respiration particularly some of the procaryotes remember back from chapter 7 that I said pretty much all living things do glycolysis right every living thing uses glucose or can use glucose um for energy to generate ATP so that means they all right oxidize glucose in glycolysis autot tropes just make their own glucose they don't have to obtain it from their environment but they're still doing it heter tropes have to get that glucose from their environment um they can also of course take in other materials as we talked as well right use proteins and um maybe some of those more complex carbohydrates and fats to go into different parts of cell respiration specifically aerobic cell respiration okay so just make sure you know that as we go on with photosynthesis don't think that plants just do this this is the way that and I shouldn't just say plants autot photo autot tropes we're talking about with photosynthesis what they do to make their glucose and then they use that glucose to do glycolysis and the rest most of them the rest of aerobic cell respiration so overview of photosynthesis we're going to focus on Photo aotr the chemo autro have a um it's a bit different process it's similar but there's obvious different enzymes some different things involved so we won't go into that we're going into photo synthesis done by photo autot tropes um and most of what we talk about here is with the ukar who have the chloroplast it's similar in the procaryotes like the way aerobic cell respiration is similar they often just may use a cell membrane instead of the organos so some Basics and this is kind of some of the basics that you may know from that if you can remember back to Middle School right it uses solar energy so light energy to produce sugars um namely glucose but plants will make disaccharides and other Strokers from it from carbon dioxide so carbon dioxide is a reactant and water water is a reactant so those are the two major reactants they use the energy from sunlight to produce so the products are oxygen and um gluc well I I say glucose C6 h12 um 06 it's really you'll see kind of half of that it's like a half a glucose and they do make glucose eventually but the process really makes two half glucoses that are put together to make glucose that that part we don't really get into but um for plants water is typically absorbed from The Roots so plants have a root system and this is why most plants are not aquatic they have evolved and are adapted to land where their roots go underground and are getting water out of the soil obviously algae does photosynthesis in water so they're taking in the water that's around them CO2 for plants is typically acquired through the air the underside of leaves have something called stomato which is shown down here they have these little guard cells on either side of their stomata that control when they open and close to take in CO2 when that happens um O2 can leave as well as water vapor we're going to come back to that but that's how um O2 gets out of plants when they're they use some of the O2 they make for their cell respiration right they need O2 as well but um when they're doing it and they have to open their stomata to let in CO2 O2 will get out cuz it's in there and so that's good for the rest of us who are surviving on aerobic cell respir ation to get that O2 um and of course they need light I should also note here I may have kind of touched on it times in the past the sugars are typically made in the leaves they're made in the green parts of the plants whatever different plants this is representing a tree here but you can think of as a flower as well so sometimes the stem can do it if a stem is green there are chlorop plot and it'll do some but majority of photosynthesis is happening in the leaves and then those sugars are transported to other parts of the plants that don't do photosynthesis right the roots aren't doing it if it's a plant that is making like a carbohydrate storage for when it can't do photosynthesis like a potato it's going to take those sugars down there um convert them into carbohydrates the flowers of a plant right the flowers aren't green because they don't do photosynthesis but they're still need to do cell respiration so the sugars are taken there so just so you know the green parts of the plant plants is where photosynthesis is happening the overall reaction of photosynthesis as I said on the last slide is carbon dioxide if we're having our balanced equation is six CO2 molecules water six water molecules using the energy from sunlight that will yield or generate sugar glucose C6 h126 and release oxygen as another product 62 molecules and this is a balanced equation similar to cell respiration as I said before it is essentially cell respiration in Reverse right this is the opposite reaction if the products here or what are the Rea ANS of cell respiration and the reactants here are what the products of cell respiration are um this is the overall reaction but it is done inside plants just like cell respiration it is done in many smaller steps there are two main Pathways that have their series of enzymatic reactions a membrane an ATP synth say again so the two um metabolic pathways here that we're going to look into and how and where photosynthesis is happening is what we call the light reaction and then the second half of photosynthesis is the Calvin cycle sometimes also called the light independent reaction I hope you're cluing in on something and that the light reaction requires light this is where water is used and oxygen is actually released and then the Calvin cycle is the second half using some things made from the light reaction is where CO2 is actually taken in and the sugar or in reality the precursor of sugar is made and so it does not require light the light reaction is occurs on a membrane on the thil covid membrane it has its own electron transport chain so it's similar to that cuz we are kind of starting where we ended um on cell respiration even though something to note here as well is photosynthesis predates aerobic cell respiration so this actually happened first and then aerobic cell respiration evolved sometime after photosynthesis um but the this is what I mean by their inverses we're starting um on a membrane and we'll have our own electron transport chain but it's going to start a little bit different it's going to start kind of how we ended so respiration and then the Calvin cycle does not use a membrane it's similar but opposite to um the crep cycle or citric acid cycle okay let's look at these reactions and where they're happening in a chloroplast so this is happening inside chloroplast in plant cells uh and algae we kind of focus on plants for this the light reaction is happening um on the thid membrane inside the chloroplast there is going to be ATP generated here something important to note a lot of times students think oh they're making ATP plants are making ATP in their chloroplast that is not ATP used for other cell reactions the ATP made in the light dependent reaction of photosynthesis is only used in photosynthesis sorry stumbling there it is used specifically in the Calvin cycle so it doesn't that ATP is not leaving the chloroplast to do go do other cell reactions plants are making their own sugars that's their end product is glucose that will be broken down and remember when it gets broken down into pyua and glycolysis then it's taken up in the mitochondria and they do make ATP in their mitochondria but that ATP is used for their other cell reactions for moving things that they need to move for growing for copying their DNA when I say moving things within the plant plants don't move much but they do move stuff with inside them so they do need ATP um the ATP they make for their other cell reactions they make in mitochondria the ATP they need for photosynthesis they make in the chloroplast and stays and is used there and then they have an electron carrier like before it's really electron and proton carrier because they're going to use those hydrogens to make the sugar and they're going to use these high energy electrons to put into their sugars which then they and us and all living things can break down to use those electrons so um they have this electron care molecule will see nadph very similar to NAD um and NAD H that we see in cell respiration happening on the thyo covid membrane cuz we need a membrane because the ATP made here is going to be made from ATP synthes and ATP synthes needs a membrane with a hydrogen gradient to be powered so thid membrane provides that gradient or the barrier to make a gradient I should say and then the Calvin cycles happening in the stroma of the coroplast so that's like the mitochondrial matrix it's like the cytoplasma of a cell right it's just that semi fluidy space inside there so we'll look at the cor plast and the little Parts more specifically but overall reaction I want you to look here light reaction is happening on the thid membrane and this is where water is taken in light is used to excite electrons and oxygen gas is going to be released and then electrons and um hydrogens are going to be picked up by nadp to make NAD pH and um ATP is going to be made by ATP synthes putting ADP and um in organic phosphate back together and then those are going to go into the Calvin cycle where carbon dioxide is going to come in and be bonded with um kind of be reformed be bonded with hydrogen and put right so that turns it organic and add electrons to become the precursor of sugars looking closely at a Chlor plast remember we saw this back in chapter 4 we have the outer membrane an inner membrane and then they have these highly folded membranes called the thilo covid so this is where there's many of them in a chloroplast so this is where um it's making ATP to use this is where their electron transport chain is made so they have many barriers there for that a stack of thids is called a Grana or granum gran plural Grom one um Lumin will be important I may just call it the thid space but the space inside the thids is the thid Lumin that'll be important um in making in that light dependent reaction and then uh the stroma which of course you can't really see because it's just this uh semifluid space in between right in there that's uh in between all these thids aquous semifluid there's proteins right there's lots of enzymes in there so this is where the light independent reactions are happening I just want to note too that the stroma is the semifluid filled space there inside a chloroplast it sounds similar to sto which are those openings on the bottom of a leaf they are different things so what is light energy we say in photosynthesis the chloroplast specifically pigments inside chloroplast are using light energy to generate sugars in that reaction so in light there is energy that essentially can excite electrons and then that energy is transferred essentially from the light to the electrons remember as I said back cell respiration think of electrons as energy right there's a reason a reason electricity it's called electricity and it sounds like electrons because we're using electrons for energy so uh we're doing this in ourselves plants are doing this by using light well they have they've evolved the ability to use light to excite electrons and then that excited electrons provides the energy to generate ATP and um are put into glucose which then they and we and other heter tropes can use for cell respiration so in this light energy the thing to also think about I'm not going to get too deep in this we do a lab over this in photosynthesis so this one kind of helps um the longer wavelengths the less energy and the shorter the wavelengths essentially there's more energy so there's a light spectrum and right x-rays gamma rays all these things infrared those are all parts of the light spectrum and they refer to essentially how big these wavelengths are and the shorter the wavelengths the more energy so that's where like microwaves right there another part of wavs um the more energy the visible light spectrum um is in the range we see what we see right there's also ultraviolet there's others but we see within the visible light spectrum and that's Roy G Biff right and then there's um and that's kind of shown down at the bottom and spread out where the shorter wavelengths are at the blue end the longer wavelengths are at the red end um so there if you're looking left to right is going the violet blue green yellow orange red which is of course the opposite of royi Biff because we're going from shorter to longer there and where the energy is and we're going to kind of look at that um or touch on that in lab when we extract pigments and where they absorb light so the last slide went in on uh the Roy G Biv and the light spectrum It reversed it around but it was showing the same concept of where there's more and less energy uh you can look at that to make sense of it if you're having issues so what do plants do plants have P well let me just say this pigments pigments are essentially defi defined as absorbing light we have pigment right they absorb light they reflect some light and we'll get into human pigments later in in the semester plants have pigments too and those pigments give them their coloration and they absorb light at certain parts of the visible light spectrum and are reflecting others where they're not absorbing it so the primary pigment in most plants the pigment that causes it to be green is chlorophyll and there are different types of chlorophyll where it's a similar molecule but slightly different in different structure so chlorophyll A and B are the two most common chlorophylls but there are others Beyond and B um we won't be going into those so chlorophyll absorbs chlorophyll A and B are shown in this graph as the solid line is chlorophyll a and the dash line is Chlorophyll B so write the dashed and the solid lines and if you look at those they absorb really well at many parts of the light spectrum except green um not super great in yellow orange especially yellow but there are some in the orange and the Chlorophyll B over here but they're very low in the green and this is why plants we think of as green is because chlorophyll is absorbing in the other parts of the visible light spectrum and reflecting green cuz that's not what they're absorbing so they plants that have a lot of green or where you see green on a plant is where they're full of chlorophyll which is the pigment inside their chloroplast that makes the chloroplast green um and is absorbing other parts of light spectrum now these pigments are embedded into the thid membrane so those remember those thids and the chloroplasts that are folded on the inside there are many many of them they also have another accessory pigment or they have other accessory pigments I should say plural they have different types um a common one is beta carotene um zanthin is another one we'll see that in lab accessory pigments are other pigments they have besides chlorophyll but most plants have them to a lesser extent although depending on um where the plant lives it's envir how much sunlight it gets in time of year it's active and some other stuff there is variation but we say accessory pigments because they have these other pigments that um are not as prevalent so kot kerene keratinoid shown on the graph here is the dotted line it tends to absorb well in the kind of blue purple blue violet part of the spectrum and is very low in the uh orange if you you notice there and the yellow orange there's like hardly any kids are not even shown on that graph there so keratinoid tend to um reflect and appear orange or orangish because they don't absorb that and they reflect it so pigments what they're reflecting is the color they are not absorbing because they're absorbing other parts of the light spectrum so in the fall when the days get shorter mostly due to day length although temperature and amount of water and some other factors but mostly day length and then some with the temperatures it starts getting cooler and amount of water the plant has gotten and is getting um cause chlorophyll to break down essentially the plant will stop producing as much chlorophyll because days are getting shorter nights are getting longer and so that accessory pigment is not prevalent anymore but the I'm sorry not it's not the accessory pigment that pigment chlorophyll is not prevalent anymore and the carotenoids are and so that's when the for certain trees like we say deciduous trees their leaves start appearing yellow and red and orange because these accessory pigments are showing up because now they're the most prevalent pigment in that plant when there's no chlorophyll there and then of course it doesn't last too long until they start breaking down and the plants stop making them as well till it goes into its kind of dormant state to prepare and make it through the winter that's a good video that if you're watching this on YouTube you may want to go back to the PowerPoint notes in Blackboard and download them and watch the embedded video I would maybe watch it after I go over it um help you put it together so I'm going to continue on with light dependent reaction happening in the thy covid membrane but do definitely watch some videos whether the embedded ones in here and or I would say and the extra resources ones uh you'll definitely want some videos to help you with photosynthesis so photo synthesis is happening on the thid membrane and um we're going to look at the stroma Andoid Lumin are different parts so write these remember you they have stacks of thids um so that's shown around here it's a phospholipid B layer membrane the th the Lumin is the space inside theid and then the Strom is the space on the outside so those are important players other important players we have a photo system one and two we're going to kind of start here and so what's a little weird is that this is called photo system 2 it was discovered after photo system 1 but it's really kind of the starting point of photosynthesis so it's a bit weird in its naming but we start at photosystem 2 that is um a large photosystem protein complex that's filled with pigments these are where the pigments are right mostly chlorophyll but there's those other accessory pigments there are carrier molecules embedded in the membrane that carry um electrons from photos system to photos system you do not need to know the names of those just know we have some essentially electron transport carrier molecules like we did in cell respiration on the electron transport chain but I didn't require you to know those molecules either and then we have another photo system so where our pigments are this is where the light's being absorbed which why you see light here uh over here and then um our electron and proton carrier molecule that are going to be used um to take these high energy electrons and hydrogen to go put them into uh sugar so nad+ and hydrogen ions are going to combine with um electrons through this enzyme that's in the thid membrane to make nadph and then down here what's also going to be very important is of course ATP synthese because I said we need to make ATP to be the energy that's going to be used so plants make the energy that they need to make the sugars in the light dependent reaction so we have um ATP synthes so there these are our major players um I'm going to go over the steps on the other slides but I kind of wanted to point out where things are here let's Orient ourselves and go through the steps of the light dependent reaction which is the plants um electron transport chain so again the thilo covid membrane here on the interior the inside of the thilo covid membrane this says IID space here is of course the Lumin we call the thid Lumin and then outside that is the stroma right that's kind of like the Matrix in the mitochondria like cytoplasm of a cell and that's where our Calvin cycle going to happen but we're going to focus here on the light dependent reaction so we kind of start here at photos system two so this is photos system 2 we're starting over here photos system 2 plants first Rea reactant what is used in the like dependent reaction is water so plants are constantly bringing in water remember they have that Central vacuu and they work to make um essentially the cell be in a hypotonic environment so water is coming in so water comes in and what happens is this photosystem is a protein complex of pigments and enzymes and carrier molecules that are going to separate but we'll get to that a minute this is essentially the opposite of the end of cell respiration so do you remember what happens at the end of cell respiration we breathe in oxygen gas and it combines with electrons and protons to make water well guess what happens at the very start of photosynthesis water is split and it's going to get split and release an oxygen gas so remember if you notice one water molecule only has one oxygen so the oxygen gas is made from every two water molecules right so two water molecules will make one oxygen gas so that is why if you're a little little confused why it says I'm going to erase this here it says half oxygen gas is because right half O2 is one oxygen which is all there is from one water molecule so for every two water molecules it'll make a oxygen gas molecule which is wonderful that is where we get our oxygen to breathe is from plant splitting water it's going to release hydrogen ions so right for every one water molecule it's going to release two hydrogen ions for every two water molecules it will release four hydrogen ions I am not worried that you know the numbers of how many all you need to know is that it's releasing oxygen oxygen gas and hydrogen ions into the Lumin it is important that these hydrogen ions are released into the thid space then what's happening there is two electrons released and that is just like at the end of cell respiration when oxygen is electronegative and combining with those electrons and hydrogen make water now water's being split so it releases two electrons what does that do that excites those two electrons to a high energy State how do they get excited to a high energy State the light being absorbed by those pigments by chlorophyll A and B carotenoids and other potential accessory pigments they're absorbing that light and that excites the electrons now we have excited electrons that essentially have energy associated with them I'm going to go on a little side note here just for you the students who may be going on to take um some more higher level classes where you go over photosynthesis most of you probably won't but I just want to make sure I'm not lying to you and so you know the truth here um the electrons come from this water and then what happens is actually when light is exciting those chlorophyll let's just say chlorophyll those pigments and electrons the electrons and chlorophyll get excited two electrons and they're actually released from chlorophyll and that's where the oy electrons come from and then the ones that were released from water replace those electrons in chlorop and then when the light hits them they get excited and so really what's happening is the excited electrons are actually coming from chlorophyll pigment but every time they get excited and move and leave when the water splits they get replaced in a chlorophyll so for this for the purposes of this class we just say they come from the water but it's actually there's another step in there that's happening so if you're into photosynthesis and doing something in Plants just want you to know that okay so we have two excited electrons now what's going to happen remember there is energy and excited electrons and that is represented by these Orange Lines they get moved by an electron carrier again you don't need to know the name of the molecule but they're going to be moved and moved across these protein complexes and guess what happens as they moved there that energy is used to bring in more hydrogen ions into the thilo covid space that's going to be important the plant um has evolved to bring hydrogen's in because it there needs to be a hydrogen gradient there essentially needs to be more hydrogens in this thid Lumen or thilo space than there is on the outside in the stroma so right low hydrogen concentration High hydrogen ion concentration how does it get that high hydrogen ion concentration the energy from electrons are used to bring hydrogens in as well as the water splitting releasing hydrogens so water splitting releases hydrogens into the thyo covid space and the energy from the electrons that they gain from photosystem to brings hydrogen into the thid space okay continuing on electron Journey they since their energy is being used to help bring these hydrogen ions in um they go to a lower energy state so they're kind of lose some of that energy that got them excited well guess what there's another photo system photo system one the second photo system on our journey I know perfect sense um is used to re excite those electrons again it's in the same way it's actually replacing the chlorophyll where the electrons get excited and come out of but we don't need to worry about that um the light is coming hitting them in this photo system one they get excited again and now they are in a high energy State and that's going to be important because they're going to get transferred to an electron carrier nadp+ so this is the oxidized form and ADP plus reductase is the enzyme that transfers it from this this molecule called ferrodoxin to nadp+ nadp+ is going to this is what this is showing pick up those electrons those high energy electrons and um bond with some hydrogen ions this will also keep the uh hydrogen ion concentration low and become nadph so now nadph is the reduced form of nadp+ it has uh high energy electrons and proton a proton here hydrogen that it is going to use with carbon dioxide in the Calvin cycle right it's gonna um attach those some hydrogens and electrons to carbon dioxide change the molecule so that it can make sugar okay so that's the Journey of the electrons remember electrons always need a place to go so the plant needs a continuous supply of nadp+ to be picking up those electrons of um I'm hoping you're kind of seeing this in relation to cell respiration nadph picks those up it's going to drop them off at the Calvin cycle which will take it back to be nadp+ where it can come back and do this again right it's just a reusable molecule to keep this this photosynthesis going all right what else I mentioned that it needs ATP so let's look down here at the bottom the thilo covid space that thid Lumen is filling up with hydrogen ions it's high so there's an ATP synthes embedded where hydrogen ions just like before are going to run through it diffuse through chemiosmosis down ATP synthes that will put ad DP and phosphate back together to regenerate ATP which of course is going to be used in the Calvin cycle which is happening in the stroma so when ATP is used over here in the Calvin cycle that will cause ADP and phosphate to be released which is why they have to continuously be put back together on ATP synthes on the thilo covid membrane to keep generating ATP okay that was a lot if you didn't follow I recommend re-watching it let's go over it again what happens before we go on to the Calvin cycle water is used as our reactant splits water is split meaning it breaks releases will release O2 gas for every two water molecules um a half of o2 gas and oxygen for every one water molecule two hydrogen ions for every one water molecule those are being released into the thilo covid space or thid Lumen where our hydrogen ion concentration is um going to be high two electrons are released those electrons get excited to a high energy state by light that is being absorbed by the pigments of photosystem 2 mostly chlorophyll that energy and electrons is going to be used to bring in more hydrogen ions specifically four but I'm not going to ask you to know the numbers um so that takes the electrons down to a lower energy State as they're bringing in these hydrogen ions they the electrons get re exited to a high energy state in photosystem one where shortly after an enzyme down the way they get transferred from this essentially electron transport chain to NAD p+ which gets reduced to nadph taking um hydrogen ion right it picked up one hydrogen ion and two electrons which now so it's now neutral um where it will use those will be dropped off at the Calvin cycle as the hydrogen ions built up in the thid space SL Lumin they will diffuse through ATP synthes uh to regenerate ATP which is also going to be used in the Calvin cycle um and these hydrogen ions right are going into the stroma so that's why it's using those electrons to constantly pump them right this takes energy pump them back in to the um thid space hopefully that makes some sense so now ATP is going to be used with nadph in the Calvin cycle where we will see CO2 right we have seen one reactant water and one product O2 but we haven't seen our CO2 and our glucose yet so we're going to see that in the Calvin cycle sort of all right the Calvin cycle also known as the light independent reaction so big clue there it just not need light to happen but you have to have light to make the ATP and get those high energy electrons and hydrogen which you are going to need for it so the light dependent reaction has to happen first first for the light independent reaction to happen but there's no actual light absorption in this part so this is a um circular pathway happening in the stroma so this is Just Happening by various enzymes that are in the stroma as um carbon dioxide is brought into the chloroplast okay so we're going to kind of start here this is again similar to like the citric acid cycle where you have these complex steps and these different molecules form along the way you don't need to know the name of any of the molecules I will say some just because um they help be me but carbon dioxide is brought in um specifically three carbon dioxide molecules per one cycle but you need um more than that to actually make the sugars so there's you don't need to know the numbers but I will kind of say some things important part here carbon fixation what is that that mean that's a a important thing fixation is when living things are taking something essentially inorganic and turning it organic or there's another way because we also say nitrogen fixation taking it in an unusable form so other than organisms that do photosynthesis carbon dioxide or some some types of chemosynthesis too um carbon dioxide is unusable it is actually right toxic and for too much of it for us so it is this gas inorganic unusable form fixation is turning it into a form that can be used by living things so they're taking it from Plants and Things that do photosynthesis are taking an inorganic gas molecule carbon dioxide and combining it using energy and um other essentially molecules they have and elements and combining it to make it a usable molecule that now can be used essentially to generate energy for living things so fixation is the first part that's where we're taking inorganic gas unusable carbon dioxide and turning it into an organic where hydrogens are going to be attached um in time solid usable form um it's essentially getting attached right it's bringing in a CO2 and it's essentially getting attached to a five carbon molecule that's already in the cycle so remember this is a cycle so it's reusing the product the end product of the cycle is getting used to bring in the inputs right so this is our reactant CO2 is consistently coming in and so this CO2 that carbon think single carbon here is going to be attached to a five carbon molecule to make a six carbon molecule it's a six carbon molecule and that's carbon fixation it's attached here but it's not actual in the form when the plants are going to use it as the sugar yet um they're going to actually break it into two three carbon molecules that um will go on to become different things so really we kind of end up with the three carbon molecules reduction it's the carbon molecule is getting reduced it's picking up those electrons and hydrogen um from nadph those are being put into the molecule you don't need to know the name but now this molecule which is g3p I'm going to say something about that in a minute um this is g3p is really what we're making here this is the precursor to glucose g3p is a three carbon molecule and two g3ps can be put together to make glucose you probably don't remember this unless if you studied it really closely but back in glycolysis when the glucose is broken down to two three carbon molecules and intermediate before it gets to pyruvate is g3p so the part of making the actual glucose the kind of what would be the glycolysis part happens later this the carbon dioxide gets it's attached to a five carbon molecule to become a six carbon molecule that is broken into a three carbon molecule but you have multiple right two for um every kind of carbon dioxide you're bringing in and so what happens is some a small amount of that g3p leaves the cycle to go become glucose and other sugars and the remainder which is the majority stay in the cycle so that it remakes the five carbon molecule needed to bring in more carbon dioxide what we call the Regeneration so rubp is a massive name molecule that the enzyme rabisco often thought of the most important enzyme ever because it does carbon fixation this enzyme binds carbon dioxide essentially onto rubp this five carbon molecule to make six carbon molecules which is the plant needs to make sugars so I'm kind of going around in the circle here many times so CO2 comes in binds with the five carbon by the enzyme orbiso to make a six carbon which becomes a three carbon gets reduced picks up those electrons and protons um energy is used here right so there's some phosphates attached temporarily um because there's energy needed for this cuz this is um right making a larger molecule where we're putting energy in so remember what that is anabolic reaction um out of this will make for every three CO2 coming in this is going to make six g3ps for every six g3ps made one lease to go make glucose and five stay in the cycle to be regenerate rabisco I'm sorry RP so that the cycle can keep happening um so really to make one molecule of glucose this needs to happen twice there needs to be like right three CO2 entering one per cycle there needs to be two turns of this cycle to make glucose which is why in the in the formula we need six co2's for every six co2's coming in that's a six not a g um to the Calvin cycle two g3ps will be made which makes one one glucose molecule and 10 g3ps will stay in the cycle to keep bringing in carbon dioxide I'm sure you're thinking like wow that's not very efficient but they need to keep g3ps in the cycle to be able to keep taking CO2 in so just the major stag is kind of what's happening with the carbon fixation bringing in carbon dioxide and organic gas to a um solid form that is going to be converted to an organic molecule reduction gain those electrons and proton hydrogen from nadph which will get uh oxidized right it's giving it up ATP is going to be used there's phosphate added here so that's that inorganic phosphate that's going to be released at some point so that we make have to make more in the light deep interaction g3p a three carbon molecule is the precursor to gluc glucose small amount of that leaves to go make glucose the rest of it stays to regenerate the molecu needed to bring in more CO2 so I try not to use too many names there um I won't ask you the names of any of these except potentially rabisco is another enzyme you should know because it's the enzyme that fixes carbon dioxide that's what you should know about it that is actually the end of photosynthesis I've got uh something more to say here about it something else you need to know but that's the light dependent reaction the light independent reaction we don't have to learn the next step where it actually puts the two g3ps together to make glucose you just need to know the Calvin cycle um if you have questions on that bring them up in lab or email me watch that again Watch the extra resources videos you'll probably need them they'll be helpful okay so uh a kind of side thing we always like to talk about when we're going over photosynthesis photosynthesis typically the way it works as described there is actually what we call C3 um three carbon dioxides brought in carbon cell respirations happening that works really well where it's not super hot super dry um where it's kind of comfortable conditions for the plant I don't know what you want to say but like good for the plant when it starts getting hotter in hotter environments and and to some extent humid environments too but hot and dry environments particularly dry environments um sometimes there's problems for plants there not sometimes always it's going to be a problem for a plant because with that normal C3 photosynthesis what I went in that's that's continuously happening throughout the day and so plants are opening up their um sto to let to take in CO2 and remember when they take in CO2 O2 gets out but you know what also gets out is water water vapor in the plant in the leaf cell of the plant water vapor is going to um or water will become a vapor gas form and leave out through the stom when it's opening to take in CO2 that's a problem for plants when they live in hot and dry environments because they can quickly get dehydrated essentially not have enough water lose water and not have enough for photosynthesis so plants that live in hot dry environments have modified have different modifications evolved adaptations to survive in those environments and they do essentially photosynthesis the same but they kind of do some things differently where they um aren't taking it in in the day like they're not always having they don't want to open up their stom in the day where water evaporate so we have C4 and more specifically cam plants for here which is a acronym for the long modifications they have for photosynthesis um and with C plants those are what you think of as succulents and cacti they have various adaptations but a major one in relation to this is um they have modified leaves they have a very heavy waxy coating so I we talked about leaves having a waxy coating I'm I'm sure you're familiar with cacti and um succulents being very waxy that helps hold in the water and one important thing which I want to note is they take in this is with Cam it's not exactly for C4 they do things a little different but with can plants they take in CO2 at night so they open their stom at night when it's much cooler to avoid um having water evaporate which means they then have to hold that CO2 until day when they can do the light dependent reaction and then they can use that CO2 for the light in independent reaction um so they kind of have to convert that's why it's called CM because they're converting their carbon dioxide to hold it until they can do the full photosynthesis but taking in opening stom at night saves a lot of water that's our cam PLS oh look and your book had a nice animation of the whole process so I do recommend watching this recommend watching Hank explain it and um asking me going over it it's a bit complicated but as I said if you if you understand cell respiration it makes this a lot easier good luck and let me know if you need anything