Biology in Focus Chapter 8: Photosynthesis

hey guys today we're gonna be talking about chapter 8 photosynthesis don't worry we will go back and do chapter 7 cellular respiration after we finish this chapter so we inserted some extra pictures for you guys to get an overall picture of photosynthesis you know from freshman year that plants take water Sun and co2 to make glucose and oxygen that's great but now we're going to take a much deeper look at it so I included a bunch of pictures for you to kind of get like a visual representation of what we're talking about because it's happening on a microscopic scale it's very hard to be like oh here's physically what's happening I can't like point to it me like well that's a little synthesis so I'm gonna show you a whole bunch of pictures that I've inserted along the way I think you should stop stop the recording make sure that you go through them and then it makes sense to maybe add them into your notes because I really think a visual representation is going to be key to help you understand this process here's another picture that I found that I put in here for you you've seen this generic little chloroplast picture probably before I like the addition of the words on this again I think that you should stop add this to your notes look at it make sure that you understand what's happening from like our bird's eye view here before we get any deeper you do have the light reactions and the dark reactions also called the Calvin cycle happening here you remember those from the rap song that we had to memorize in class but again I'd stop this and make sure that you understand the basic idea of what's happening in our chloroplast before we go any further okay so photosynthesis it is a reaction that's going to convert light energy or solar energy into chemical energy which in this case is going to be glucose it's our food of plants okay this is happening in our autotrophs so autotrophs are things that can provide nourishment for themselves so we are not our Latrobe so we are heterotrophs because you cannot stand outside and eat your lunch you have to go physically to buy food prepare food somewhere and consume it okay we're talking about plants and other photosynthetic organisms some protists and some bacteria okay so this process is highly organized and it's highly organized because it's a whole bunch of these key players and each one has a specific role and you're gonna see how complicated this gets later but basically basically we have a structural organization or photosynthetic cells that includes enzymes and other molecules that are all grouped together within a membrane in order to help us carry out the process of photosynthesis okay this organization allows for the chemical reactions of photosynthesis to proceed efficiently every single little moving part has its assigned job and as long as it occurs correctly then we are going to have glucose at the end of the day which is what a plant's going to need okay our chloroplasts are structurally similar to and likely evolved from photosynthetic bacteria this kind of goes back to the theory of endosymbiosis that we talked about when we talked about chapter 4 the tour of a cell so chloroplasts are the site of photosynthesis in plants so we have this big overall reaction to make glucose now where does it happen it happens inside of the chloroplast so the leaves of a major photosynthetic organ of our plants you think about on most plants you know the leaves are green well green means that there's chlorophyll there we're gonna talk about florrick and a little chlorophyll in a little bit but chlorophyll is what's actually going to be you know the pigment that captures this light it's actually the next thing that this says here right so it's the green color from the chlorophyll the use of our plants contain our chlorophyll because there's a lot of chloroplast there okay and so the green pigment lies within the fluoro class so wherever there's a chloroplast is full of chlorophyll that's what makes a plant green okay your chloroplasts are found mainly in the cells of our mesophyll tissue here in our Leafs so we have the anterior tissue mezzo means middle so with the anterior part of our leaves that have that mesophyll tissue and that's where most of our photosynthetic reactions are going to be taking place okay each cell of our mesophyll is going to contain roughly 30 to 42 chloroplasts and each one of these two carrying out the process of photosynthesis to provide food for the plant so we're gonna have carbon dioxide that enters an oxygen that exits the leaf through microscopic pores called stomata okay you might have done a little lab where you did clear nail polish on the under part of a leaf and if you peel it off it looks like it has a little tiny leg bumps and holes in it well that's because it does okay just like you have pores and you're scanning on your face our leaves have have these little tiny pores - there called stomata they're just like your lungs right your lungs are used for gas exchange well plants don't have lungs but they have stomata and they're used for gas exchange notice I use the word exchange it means that you're like getting and giving okay so while plants are bringing in carbon dioxide they're releasing oxygen both of these gases are being exchanged by this particular structure the stomata okay um the chlorophyll is going to be inside of membranes of Styla coins that look like little tiny green stacks of pancakes that are inside of our chloroplasts and the thylakoids can be stacked in two columns let's the stack I'm talking about looks like little sack of tiny green pancakes it's called a grandma or grandma would be one okay we also have chloroplasts that contain stroma it's the dense interior fluid you can kind of think about stroma similar to like the cytoplasm of the cell so like if you have the chloroplast then within that you have your thylakoids and your stacks of you know thylakoids called grana around the outside of all that you have like a jelly consistency of material called the stroma there so that's kind of like the cytoplasm that's kind of like a cushioning but we also have reactions that occur in the stroma as well so here's some pictures of what we were just talking about we said that we have the photosynthetic organized the leaves and specifically we're talking about the medical tissue which is the middle layer which you can see up here in this image so it's the mesophyll layer that actually contains the chloroplast roughly 30 to 40 um chloroplasts within our cells here you also see the little stomata these are going to be used for gas exchange again carbon dioxide will go in for photosynthetic use and then as a by-product we'll have oxygen coming out and here's the overall structure of our chloroplast you can see that you have the little stacks of these little thylakoids here each little disc is the thylakoid the whole thing is called a random or multiple is called grana so inside of that you can see that you have some open spaces okay like the open space is going to be color stroma whereas we have you know the other material inside like the thylakoids base and so on okay so we're really going to be looking at tracking atoms and electrons as we go through the process of photosynthesis okay now let me know where it's occurring we're going to get into it a little bit more and I don't want this slide to confuse you because like even I read it I was like wait a minute we're not gonna talk about this so let me just clarify for you you know that plants take water Sun and co2 to make glucose and oxygen okay so you look at this this equation here and you say hey carbon awesome carbon dioxide we got that going on also water perfect okay light energy called sunlight or solar energy perfect we're making some c6h12o6 it's a 1 to 2 to 1 ratio carbohydrate called glucose and then we also have oxygen perfect okay but what is this where did this come from this is called water h2o why is that a product of photosynthesis if plants are walking around making oxygen and water why do we need anything else this is all that we need plants you know it's giving us everything that we need ok so I don't want you to focus on the water okay because do plants technically make a little tiny tiny bit of water yes its water vapor though so let's talk about it just briefly and then forget about it okay I want you to pretend like we have a big fat line here and then like this is gone I don't want you to worry about this atomically you need to understand that that's where the extra hydrogen's and oxygen are going it's water vapor okay but we're not focusing on this for the intents and purposes of the class so essentially you have oxygen that's released from the cleavage of co2 okay and that oxygen that's floating around can pair up with all these extra hydrogen's that are also floating around in this whole reaction of photosynthesis if you have hydrogen and you have oxygen come together it makes water specifically h2o okay so this would exit the plant as water vapor it's a byproduct a lot of textbooks don't even include it they just leave it out altogether this one happened to include it and I don't want it to confuse you okay so for the intents and purposes of this course don't worry about it you are worried about the process of photosynthesis as producing glucose and oxygen and that's it okay you do need to know where the oxygen comes from okay understand that when you have the carbon dioxide and you cleave off the carb of the carbon here you have remainder of oxygen that can pair up with hydrogen and create this by-product that we're never going to talk about again okay but the oxygen that's actually released from the stomata the oxygen that you and I are breathing in all the time comes directly from the cleavage of water during photosystem one so water goes in and we're going to cleave it to create the oxygen that's being released and we'll look at that later you do need to know that that you do not worry about this thing over here we're never going to speak of okay so the splitting of water like I just mentioned so the chloroplast is really special because splitting of water is something that's a little difficult to do so this chloroplasts are capable of carrying out this process in order to grab the hydrogen's that they need right so chloroplasts are going to split h2o called water into hydrogen and oxygen and they're going to incorporate the electrons from the hydrogen into sugar molecules called you know glucose and and they're gonna be releasing the oxygen as a byproduct so this is a very rare reaction that happens but I mean like okay plants take up most of our you know playing it whatever it next to water so like is it really that rare but like other creatures can't do this so this is pretty cool that plants can do this right so they're essentially gonna just hang on to those hydrogen's in order to use them as a source of electrons to help create their sugars but then that oxygen they don't really mean so they get rid of it like almost right away right so it's very early on in the process and we benefit from that because yellow we need to breathe in that oxygen okay so here's the overall process of where everything is coming from so like I said you need to know that we are gonna take water and we're gonna break water and what are we gonna do with that we're going to take the hydrogen's and we're going to utilize them for our sugar and then this other thing we're never speaking of and we are also going to use that oxygen as a byproduct to release the atmosphere for our you know other organisms that need to live on oxygen okay so this is where our reactants are getting broken down and where they're donating all of their atoms okay so photosynthesis is a redox process or redox reactions if you take chemistry you know that this is a reduction and oxidation process so photosynthesis reverses the direction of electron flow compared to respiration so basically it's just an opposite happening here so photosynthesis is a redox process in which water is oxidized and carbon dioxide is reduced and we're gonna look at a picture of that in just a second and it's gonna make more sense okay so photosynthesis is an endergonic process which means we need the input of heat or energy for it to happen the energy boost is provided by light okay the photon of light that's gonna go in and excite our electrons so here's what a redox reaction looks like so this happens to be photosynthesis and notice that there is no like nadi no no happening on the end of this year this is this is the correct photosynthetic equation okay so we have carbon dioxide that's becoming reduced what does that mean there is an acronym for this it's oil-rig if we're talking about reduced that's the rig part R IG reduction is gain what are we gaining we're gaining electrons in the form of hydrogen so we have carbon we have oxygen but now all of a sudden we have hydrogen because we're gaining electrons okay reduction is gain reduction we're gaining electrons in the form of hydrogen here oxidation the oil part of oil rig oh I L oxidation is loss so here you have hydrogen's and you have oxygen and now at the end you only have oxygen it's oxidized because oxidation is rude oxidation is loss so you were losing electrons in the form of hydrogen here so just say that a few times to yourself oxidation is loss of what electrons okay so what happens literally so rude I'm just gonna keep going because it's gonna take me forever oxidation is loss of electrons in the form of hydrogen we're losing hydrogen here perfect that's oxidation here we have reduction because reduction is gain of electrons weird electrons this is so rude I'm so sorry so we're doing that in the form again of hydrogen so carbon dioxide now we're gaining hydrogen's here it's being reduced to become sugar okay so our two stages of photosynthesis this is a entrance of the crackheads echo and Reagan my monsters um a two-stage process here this is a preview this is a bird's eye view so we're starting like big screen and we're gonna go zoom all the way in and focus on just one reaction time in just a second but the overall preview so photosynthesis consists of our light reactions the photo part of photosynthesis using light to make something ok and then the Calvin cycle is the synthesis part we're actually going to be creating combining carbon carbon with other molecules in order to create our g3ps which will eventually turn into glucose okay so we have the light reactions in the thylakoids that's going to be where we have the splitting of water which again is really rare and really cool and then we're gonna be releasing oxygen okay that's the first step the light reactions are the very first step think about what I just said that we're releasing oxygen in the first step if there's two steps in the first step what if you made glucose in the first step why would you need a second step if the plant got what it wants why the heck would you go on and do another whole step you wouldn't so there's two reactions that happen and the first reaction you get a waste product that's why you have to go on and do the second step and that will make sense as we look at a picture and I'll point it out to you there as well okay so again in the light reactions we have the splitting of water and we have the release of oxygen very important okay we are going to reduce the electron acceptor and ADP plus two NADPH now again what is reduction reduce what is that ROG reduction is gain gain of what electrons how do we gain an electron what does it look like it looks like an H called hydrogen so now we have any DP H because we just got reduced we're adding an H because reduction is gain rig oil-rig okay so generate ATP from ADP by adding a phosphate this is photophosphorylation okay so we have ADP floating around we're adding another phosphate group to go through photophosphorylation because we're utilizing light in order to generate ATP photo is the light part phosphorylation needs to add a phosphate group we're adding a phosphate group to ADP to create ATP okay so in the Calvin cycle that's a second step they're also called the dark reactions which is a little bit misleading but light only interacts with the light reactions okay light is not utilized in the Calvin cycle okay so the Calvin cycle that happens in the stroma remember that that's like equivalent to the cytoplasm okay forms sugar from carbon dioxide using that ATP that we just made in the light reactions and that NADPH that we just made in the light reactions so if we didn't do the light reactions we wouldn't have these two things which means that we would not make sugar okay so we're going to form sugar from carbon dioxide which is in the air okay and that enters through the stomata using ATP and nadph so where do these two things come from ATP NADPH they came from the light reactions okay so the Calvin cycle begins first so there's three different phases the first phase is called carbon fixation and it's going to incorporate carbon dioxide into organic molecules okay here's an overall reaction I was talking about we have like reaction like reaction here and our Calvin cycler dark reaction we're gonna call this step one and we're gonna call this step two so in step one if we made glucose here why the heck could we do all of this what is this garbage if we made glucose right away that would make any sense right I'm gonna tell you that this will be a quiz question where all of these will be like little a/b c/d and there's gonna be like Oh which one of these represents oxygen oxygen is a product you know that so it's going to be coming out so you got a 50/50 shot it's good that the green arrow or the blue arrow but think about it does the plant want oxygen no so it's going to make it first because if it made glucose first why the heck would we do all of this jazz we would not want to do that it's just a waste of energy look at this we're using ATP oh my gosh that's a waste of literal energy okay so again if like all blanks it would make sense that you're making the waste product first because otherwise why would you do a second step if you Maine Blue Coast here it would make no sense to keep on going okay so just remember that also Calvin cycle si si si goes into si si it's very simple okay also you know the light reaction is really really cool because they can split apart water it's really me and that's where our oxygen comes from okay so the light reactions convert solar energy to the chemical energy of ATP and nadph why do we need those two things because that's how we're going to create sugar in the Calvin cycle okay so chloroplasts are solar-powered chemical factories okay they're thylakoids transform light energy into the chemical energy of ATP and NADPH and you remember this from our little rap song as well it's so nice that I made you learn that so here's another picture that I put in okay we are looking to track our NADPH and our ACP this is the overall process of the light reactions this is a little bit more complicated than this picture this is a light reactions cute it's two words and it's on something green okay but like this is what's actually going on there that we're gonna talk about okay so like I said what are we doing here it's a chemical factory to make NADPH and ATP where are those two things going to go they're going to continue on and they're going to go into the Calvin cycle step two the dark reactions okay that's exactly what's happening here we're looking to create these two things to then push them into the Calvin cycle okay so this is actually what's happening this is another picture that I snatched from somewhere else online the descriptions really great the pictures really great again please pause and look at these especially after i already talked about it you can go back and be like wait what the heck does she say about this oh yeah that makes a little bit of sense imma stare at this picture and hope that some through some sort of diffusion osmosis sort of electrical impulse something that it gets into my brain hole so please make sure that you look at these okay all right there's a bunch of slides in here that I took out about the visible spectrum of light and spectrophotometers in blah blah blah I don't care about that I'm going to refer to the photosystems as p680 and P 700 and I just want to tell you what that means 680 and 700 or referring to nanometers that's what this little mm means if we're talking about the visible light spectrum like this is what we're like 680 would be like you know like yay and then like 700 is like okay cool so if it's here we're actually going to be reflecting green because it's it's mostly like absorbing red mostly okay but then okay that's that's why we see green okay let's talk about that so that's the visible spectrum of light just so you know cool okay P six eighty and P 700 is literally talking about the photosystems and then the nanometers of light that they absorb okay cool so the light receptors here pigments are substances that absorb visible light guess what visible light boom there it is K the rainbow core just you know Rajee viv and all that you know that okay great okay so different pigments absorb different wavelengths okay a pigment that we're focusing on chlorophyll because why it's in plants we're talking about plants we're talking about photosynthesis okay so wavelengths that are not absorbed are reflected so if we're over here we're absorbing these we're going to reflect things like this this is why you get you know the colors like this direction okay now you don't have like purpley little sometimes those are actually really cool-looking mostly green we're focusing on like green leaves because they do not absorb green light they reflect it okay so leaves appear green because chlorophyll reflex and transmits green lights focusing on the green because chlorophyll is what it's green okay it's a pigment that absorbs light but not green light because it reflects it cuz that's what you see so that's what that's what's happening here that's why we see green beautiful love it okay so absorption spectrum blah blah blah I'm not going to be talking about all that but we do have chlorophyll a and we do have chlorophyll B and these things called carotenoids okay so chlorophyll a and Beebe's are very similar wavelengths chlorophyll a is our main photosynthetic pigment chlorophyll b is a secondary pigment and carotenoids are kind of therefore like the aftermath okay to help prevent light damage and things to our plants but we'll talk about those more and later you need to know chlorophyll-a is the main photosynthetic pigment in plants okay Hey look at that I just said that it's like I read this before okay so chlorophyll a is the main photosynthetic pigment in plants beautiful so accessory pigments like chlorophyll be like I said we don't really use that a whole lot but it does broaden the spectrum of light available for photosynthesis and then there's a little bit of a structural difference between chlorophyll a and B it's on the next slide it's literally like two atoms difference okay and then our carotenoids absorb excess of light that would damage the chlorophyll otherwise it's also the reason why we can get different variations in color in our plants as well okay so this is what I was talking about the structure of chlorophyll a and chlorophyll b so like the only thing that's different is a little group right here instead of a methyl group it's like this little like shell group okay beautiful great excitation of chlorophyll by lights this is where it starts that's happening it's about to happen okay so when pigments absorb light pigments called what called chlorophyll mostly chlorophyll a okay it absorbs light this sort of ducks okay it goes from a ground state to an excited state which is very unstable okay so when exciting electrons are going to fall back down to their ground you know not crazy but just ground States okay protons are given off and it's an afterglow called fluorescence I'm gonna look at a picture of that in a second okay so if illuminated and isolated solution of chlorophyll will fluoresce or give off light and heat boom look at that fluorescence okay we don't see plants that glow because there's somewhere for all that energy to go and it's called the electron transport chain and we're gonna look at that in a minute okay but we don't see glow-in-the-dark plants all the time because they're somewhere for that energy to go now if it was just in a contained flask here like this Erlenmeyer class is full of a fluorescent material it would fluoresce it would glow because it has been excited and it's illuminated okay so a photosystem we're gonna talk about two of them like I said p680 and P 700 P stands for photosystem we're gonna be talking about two different photosystem so what the heck it's a photosystem it is a reaction center it's a complex of a whole bunch of different moving parts and enzymes and it's associated with harvesting light complexes or light harvesting complexes so photosystem is a reaction center that's the p680 in the p700 parts okay it's a protein complex that's surrounded by light harvesting complexes will this make sense because you know plants do photosynthesis it's when we harness light and then make sugar so like we need light harvesting complexes beautiful okay so these are pigments called what called chlorophyll mostly chlorophyll a they're gonna transfer our energy of the photons to the reaction center that's called P six eighty and P 700 okay so this is kind of like what's going on here this is a little complicated like the molecular structure of this like the actual beta sheets an alpha helix sees and think okay cool we're gonna look at this picture cuz a little bit more friendly we have a photon of light coming in it's always like this a lightning bolt is it actually lightning it's just sunlight it's visible light its sunlight okay here we have our photosystem okay so we have the purple part here that has our light harvesting complexes pigments things like that and then the century of your reaction center complex okay so that's the overall structure over photosystem ok primary electron acceptor in the reaction center accepts excited electrons and is reduced again reduction is gain our IG oil-rig our IG reduction is gain as a result okay solar-powered transfer of an electron from a chlorophyll a molecule to the primary electron acceptor is a first step of the light reaction one more time for those of you in the back we have light it's coming in it's going to go into chlorophyll a that chlorophyll a molecule is going to hand off the excited electrons to a primary electron acceptor primary means like first electron acceptor makes sense because it's accepting the electrons from who from the chlorophyll a okay that's a first step of a light reaction okay there are two types of photo systems in the thylakoid membrane as promised photosystem 2 functions first before you're like wait to comes number one yes because they were named in the order that they were discovered okay so photos two was discovered after photosystem one had already been named why didn't they change in the name I don't know I wasn't wives I what my parents like probably weren't even alive okay so photosystem two actually comes first just remember that it's not that complicated okay two comes one okay photosystem two comes first and it's best if absorbing a wavelength of 680 nanometers as promised that's where that p680 comes in p680 is the reaction center of photosystem two because it's absorbing that wavelength of light okay alternatively photosystem one which actually comes second - and then one is called P 700 because why it absorbs wavelength 700 nanometer light okay beautiful that's the reaction center there okay so you have this linear flow of electrons and we're going to be following this in order to create our ATP and nadph because those are very important we're gonna pass them off into the Calvin cycle okay linear electron flow involves the flow of electrons through both photosystems two and then one because reasons to produce ATP and NADPH using light energy or solar energy okay so here's the steps linear electron flow can be broken down into a series of steps there's something like eight of them so here we go okay photon hits a pigment light hits chlorophyll a and it's energy is passed among pigment molecules other chlorophylls until it excites p680 which is the reaction center in photosystem two which comes first okay and excite an electron from p680 within photosystem two is transferred to the primary electron acceptor the first thing that actually holds on to those electrons and we now call it P six eighty plus don't get too bogged down by that I'm not too worried about that last part okay step three water is split by enzymes and the electrons are transferred from the hydrogen atoms to the p680 plus thus reducing it to just key 680 as a result we have oxygen that is released as a by-product so again where did that water or where did that oxygen come from I just told you because I'm done it came from water okay so oxygen is released as a byproduct why because we split oxygen nope words are difficult because we split water we use the hydrogen to make this plus sign go away by reducing it and adding in electrons because electrons are minus or plus plus and a minus minus get back to zero p680 and then after we remove these hydrogen's we have these leftover in oxygen okay oxygen is released as a byproduct and it's in the first step because the plant does not want oxygen okay so this is where we're at right we got the light coming in it hits photosystem two the chlorophyll is going to have the excited electrons are gonna start passing down the electrons we have the splitting of water as it's coming in and we're releasing oxygen beautiful okay here's another example of that because this is what you're used to but this is what we just said okay you got light it's coming in all right you got all of the chlorophyll molecules that are bouncing around all the electrons are getting all excited and they're passing them down and then we have the reaction center p680 is going to accept those electrons okay and then we're going to have the splitting of water and the release of oxygen and then look at what we have to go through next Wow it's a lot okay so each electron falls down an electron transport chain from the primary electron acceptor of photosystem 2 all the way down to photosystem 1 so essentially it's just like passing a ball between a whole bunch of different people and the ball is an electron okay the electrons are very excited it's like passing this energy down of these excited electrons down a huge conveyor belts of different enzymes and protein complexes in order to eventually reach photosystem one okay energy released by the fall drive the creation of a proton gradient across the thylakoid membrane diffusion of these H+ hydrogen protons across the membrane drives ATP synthase okay this is what we're talking about electrochemical gradients back when we talked about tour of a cell in chapter 4 when we hit cellular transport okay if we gonna we're going to pump a whole heck of a lot of these protons into the thylakoid membrane and as they come back because they were going to want to drift back from high to low concentration because now we've created a very high concentration diffusion will drive them back down the concentration gradient they're going to spin this rotating complex called ATP synthase that's going to create ATP we'll look at that later step six in photosystem one which is the second photosystem because reasons in photosystem one okay like photosystem two the transferred light energy excites the reaction center called p700 again the number is the wavelength of light that it absorbs causing it to lose an electron to an electron acceptor so now it's the same thing P 700 plus KP 700 plus accepts an electron passed down from photosystem two which actually comes first viola the electron transport chain which will return it to just regular P 700 okay so the excited electrons fall down an electron transport chain because it's transporting electrons in a chain of events from the primary electron acceptor of photosystem 1 to the protein ferredoxin which is abbreviated as FD ferredoxin okay so that is at the very end that is the primary electron acceptor at the very end okay so we have our electrons that are transferred to nadp+ reducing it our IG reduction is gain we're adding a hydrogen which is really electron okay reducing it to NADPH and it's available for the reactions of the Calvin cycle because we're going to send NADPH and ATP into the Calvin cycle to help us turn that carbon dioxide into glucose from g3p first but then glucose okay this process also removes an H+ from the stroma which again is like the cytoplasm okay the energy changes of electrons during the linear flow can be represented in a mechanical analogy I took that picture out you just need to know that these excited electrons are current or consistently passed from one acceptor to the next until it reaches the end of the electron transport chain because it's back into its like ground state that's it we're slowly decreasing in energy as it's quote falling along the whole way okay so we're gonna take a time out for just a second to compare the chemiosmosis and chloroplasts and mitochondria okay what the heck is chemiosmosis okay remember I was Moses it's a thing like water moves from high to low concentration chemiosmosis is basically when we have chemicals moving from high low concentration and it's used to generate energy for something else so in chloroplasts and mitochondria we're going to generate ATP by chemiosmosis but they use different sources for this energy so in the mitochondria which is not what we're talking about right now but we're gonna talk about it when we talk about cellular respiration cuz that's where PGP is created powerhouse the cell okay the mitochondria is going to transfer chemical energy from food to ATP because we eat things and then make ATP actually this also occurs after we already generate that glucose that is a food source that we're gonna turn into ATP okay chloroplast transform light energy into the chemical energy of ATP so we go from food to ATP and then chloroplasts light to ATP so like yeah there's pretty big difference okay but the spatial organization of chemiosmosis differs between the chloroplasts and mitochondria but they're also show some similarities so while the overall mechanism is a little bit different there are a lot of similarities and when we actually learn that process you'll see that they are kind of similar and you'll be like what the heck these are too close I'm going to get them confused you're right so make a really good study guide card for the test okay pictures are very helpful if pictures worth a thousand words you're right they sure are okay okay so in the mitochondria we have protons that are pumped the inner membrane space and drive ATP synthesis as they diffuse back down into the mitochondrial matrix and in the chloroplast so we have proteins that are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma guess what that sounds real similar hmm that's cuz they are okay so the process is different because we're going from food energy to ATP and then light energy to ATP in the chloroplast so the mechanism is a little bit different but like how we actually go about creating this ATP is pretty similar basically and unless it's an electrochemical gradient that's going to diffuse back down through the concentration gradient in order to generate ATP at the end of the day that's the moral of the story again if this sounds like I'm just spitting chemistry I am but also pictures are helpful so go back and look at the pictures so put your textbook read it it's really helpful it's a whole bunch of words that like really make it clear okay okay so we have ATP and NADPH that we produced in our light reactions okay the produce on the side facing the stroma okay and then that's where the calvin cycle takes place so they're produced on the correct side of the membrane so that we can go ahead and just like feed and straight on into the calvin cycle which is really nice okay so in summary the light reactions generate ATP and increase the potential energy of electrons by moving them from water to NADPH okay remember that we split that water we took those hydrogen's in the form of you know like electrons like okay and then we slap them on to nadp+ to create NADPH and what do we do with that oxygen we released it through the stomata for us to breathe okay so again overall process we just talked about this and that was a lot of words and a lot of carbon dioxide that I just created in order to say those words to just talk about this well why is this important because of this this ATP and this NADPH we just had to create that from here in order to drive this next reaction okay so we're going to use these products to go into the Calvin cycle because the Calvin cycle is even worse than like reactions ok that's what we're actually going to create the sugar for the plant and that is what the plan is after and it is very important here's the picture straight out of your textbook ok this is actually a really great image of everything that's going on here there's even more words associated with this than what I said okay we got the photosystem 2 happening here you got your photon of light going in it's exciting the electrons in the chlorophyll get your reaction center you got your splitting up the water to release the oxygen ok you have it talked about bringing more of our words or difficult protons into the thylakoid space you have these other like handoffs that are happening here like plastoquinone and cytochrome c complex and then plastocyanin I believe is what that one's called and that's going to hand it off then to photosystem one which the terminal electron acceptor is going to be our ferredoxin which we did talk about which is abbreviated FD okay and then we have our nadp+ reductase reduction is gain okay we're gonna add on we're gaining an electron essentially here okay so we're creating NADPH and then again we're creating this like increase of our hydrogen here which is going to flow back out because it's a high concentration to a low concentration as it goes back out through this transport protein it's going to create ATP hey ATP synthase means to create it's the enzyme that creates ATP by photophosphorylation and that's where we create our ATP guess what these two products are now going to move into the Calvin cycle again pictures are worth a thousand words please make sure that you pause and look at the pictures they're really important okay this is an overall picture of the Calvin cycle and I really like this one because it includes a little one here's what's happening - this is what's happening here okay all of this is really important and I like that the pictures are all color-coded I like that there's steps for you to read a long way which are like just a little bit different than what it says in your textbook just make sure that you go back and look at these because we just talked about the light reactions now the Calvin cycle is something completely different and you're looking at that and you're like okay cool it's a circle you need to come back to this after then spitting some game about all of the Calvin cycle steps okay here's another picture for you a little bit simpler you can see oh great one two three four four steps I got this okay but like it's a lot still you know what I mean okay so you make sure that you come back and that you understand what's happening yes you have your you know overall phases that are happening here but like this and it does it in six steps like do I care about the number of steps not exactly but I want you to know what's happening along the way for the entire process okay this is also a little bit janky but I really like this picture because it's basically broken down into three steps so you have carbon fixation reduction in sugar production and you have regeneration those are the three main steps of this overall process I'm like here it's written out very well for you I would pause this zoom in on it flip it if you're on a smartphone or a tablet or something and you can like you know zoom in on it I recommend that add anything to your notes that you don't already have there and then you know come back to this one I'm done creating some carbon dioxide about it this whole process okay alright so we previously talked about the light reactions we can do it this is the second half we're gonna make it okay this is the Calvin cycle also called the dark reactions okay the Calvin cycle uses the chemical energy of ATP and nadph that we just created to reduce carbon dioxide now what is reduction reduction is gain what are we gaining electrons what are we gonna become c6h12o6 called glucose okay so the Calvin cycle like the citric acid cycle don't worry about that just ignore that we'll come back to that later another time the Calvin cycle regenerates its starting material after molecules enter and leave the cycle this is important but we're gonna look at some pictures and you'll see why it's important okay so um bla bla bla it's your cat who care the Calvin cycle is anabolic what is anabolic think about anabolic steroids I like to pick things up and put things down how you grow muscles ain't about steroids like you know like illegal ankle okay so anabolic means building reactions why are we building because we have co2 we're gonna turn it into c6 h-12 o-6 that's definitely a larger molecule we are building that up okay it builds anabolic builds builds anabolic oh my gosh it's like naming the same thing because they do okay it builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH okay so carbon enters the cycle as carbon dioxide where did this come from it came from the atmosphere from like our little hot breath when we're breathing and I'm speaking right now and generating a lot of it for the plants save the plants okay so carbon dioxide enters the leaves through the stomata okay so carbon enters the cycle as carbon dioxide and leaves as a sugar named glyceraldehyde 3-phosphate okay for net synthesis of one g3p which you need two of those to make a glucose okay so from the net synthesis of one g3p okay the cycle must take place three times fixing three molecules of co2 now if you're intelligent here and you can say well if we need to g3ps and you have to use three molecules of co2 to make one then I need six molecules of co2 to make two g3p also six co2 6c okay c6 h-12 o-6 okay because we need six carbons I hope you got that so the Calvin cycle has three main phases it has the carbon fixation stage the reduction stage and the regeneration of the co2 acceptor stage three stages okay each textbook calls them something like a little bit different which is why that weird janky sideways picture calls what calls from different steps but what's happening is still the same cool okay phase one carbon fixation you know this again from a rap song again you're welcome okay so carbon fixation involving corporation of carbon dioxide molecules into rib you loose this phosphate this is why we use acronyms cuz no one wants to say that okay Ruby loose 6 bisphosphate this means like two two phosphates okay so this is our you b.p are you b.p rubp using the enzyme rubisco which we learned in our rap song okay it's like the most common enzyme like in the world because plants okay so are you BP is reveals bisphosphate so I'm going corporation carbon dioxide molecules into reveals this phosphate using Rubisco so we're gonna turn co2 into this using this great this picture is not really helpful here thanks textbook alright here's the overall thing we're going to have two turns of this overall essentially so we're inputting three carbons this is a this little circle and spoiler alert at the carbon we're gonna input three carbons as three co2 three carbon dioxide's now remember that's gonna make one g3p which I said earlier we need to g3p so this process it gonna happen twice okay so input three carbons as three carbon dioxide's you see Rubisco it's an enzyme so we have rubp that's going to meet up with our co2 in order to create see we have one two three four five carbons and rubp rib you loose bisphosphate okay that's what this is this phosphate means two phosphates oh my god look at that it's like the name matches okay co2 has one carbon so we have our 1 2 3 4 5 oh my gosh 6 because it came from right here ok we're just showing it 4-1 but this is really happening three times at each of these steps ok and then we're going to have 3 phosphoglycerate ok this is a three carbon basically you're like cleaving this okay and then you're going to add an ATP in here and you're going to slap one of the the third phosphate onto a 1 3 bisphosphoglycerate because here phosphoglycerate means that there is one phosphate at the end of a glycerate molecule here so essentially we just like in half essentially okay so then here 1 3 bisphosphoglycerate position 1 position 3 oh my god it's like it matches ok we're gonna go through we're going to utilize that NADPH that we brought in from the light reactions we're going to oxidize this in order to oxidation is loss we're gonna be removing this terminal group here in order to donate some electrons okay we're going to generate some g3p the reduction step here okay because we're reducing this molecule ok glucose and other organic compounds g3p is our output here because g2 g3ps are going to make glucose for us but then we also have g3p notice that there's six of them here one of them goes on to make glucose that's why we need to do two times this whole reaction okay five of them are gonna go on because remember there's three here and if we're doing 3 times 2 is 6 so 1 plus 5 is 6 this will make more sense if you read the textbook I promise I promise ok we have five of these g3 peas that are actually gonna go into the regeneration step two go make more ruv piece because if we don't have any rubp then there's nothing for our carbon dioxide to come in and attach to with the help of Rubisco right so if we don't have this molecule then this whole thing's not gonna happen so only one of the you know overall carbons that we put in the six carbons that we put in one of the things that we get out out of the six total products actually gets to go on and become glucose that's why we got to do two terms of it okay again this is exactly word for word in your textbook written out very well with little blue numbers that indicate all the steps there's well paragraphs to tell you about it all please go back and read this please it's complicated you just heard me explain just like a once over of this there's even more detail than that please please please read it okay okay these two is gonna be reduction so we talked about phase 1 carbon fixation so we're putting our carbon dioxide with help of Rubisco onto rubp okay carbon fixation beautiful okay so cool phase two reduction involves the reduction of an phosphorylation of 3 phosphoglycerate again so this is a phosphate in position 3 on a glycerin molecule oops 3 phosphoglycerate position 3 3 carbons k cool ok to create g3p g3p g3p notice that there's a things that happen in between okay next we have the phase three which is regeneration so like I said it involves the rearrangement of g3p to regenerate the initial carbon dioxide acceptor or acceptor which is the rubp because remember the very first thing that happens is that carbon dioxide comes in and it pairs up with rubp because Rubisco helps to attach them together okay that's creating our first products here which is through carbon fixation so we need to regenerate that rubp so we're going to use a lot of the g3p we just created to go on and create more rubp for the next carbon dioxide that are coming in okay this is talking about like the evolution of the overall like why this process is happening the way that it does so evolution of alternative mechanisms of carbon fixation hot and arid climates so other types of plants you know like cacti and like hot arid climates are gonna do this whole process like pretty similarly but like with minor differences so adaptation to dehydration is a problem for land plants sometimes requiring trade-offs while other with other metabolic processes especially photosynthesis on hot dry days plants close their stomata remember that stomata are their little pores in the under part of the leaves that are used for gas exchange to allow the carbon dioxide in the oxygen out that's what the stomata are which is going to conserve water because it also but it also limits photosynthesis right if you close up those pores during a hot day then those plants are gonna hang on to more water it's not going to be transpiring off the top of the plants but if you are closing those stomata then there's no carbon dioxide that's going into the stomata either which means no carbon dioxide means you're not gonna make any glucose so there's no photosynthesis happen so the closing of the stomata reduces access to carbon dioxide and just said that and causes a buildup of oxygen which can be very bad for the plant actually these conditions favor and apparently wasteful process called photo respiration okay so most plants c3 plants or our normal plants that don't have any special mechanism it's just straight photosynthesis okay initial fixation of carbon dioxide via Rubisco forms a 3-carbon compound called 3-phosphoglycerate we just looked up that a few times again pictures are going to be very helpful in photorespiration Rubisco adds oxygen instead of carbon dioxide in the calvin cycle reducing oh sorry producing a two carbon compound so photorespiration decreases photosynthetic output by consuming a lot more ATP oxygen and organic fuel and releasing carbon dioxide without producing any ATP or any sugar but it's releasing carbon dioxide which it's not able to get any other way because the stomata are closed in these plans that are doing photo respiration so photorespiration may be an evolutionary relic because Rubisco first evolved at a time when the atmosphere had far less oxygen and more carbon dioxide so photorespiration limits damaging products of light reactions that build up in the absence of the carbon cycle so again photo respiration is when you are going to add oxygen instead of carbon dioxide in the calvin cycle in order to produce a 2 carbon compound ok it's also going to be releasing carbon dioxide here without the production of any ATP or sugar because you've used a lot of ATP and other organic fuels ok but if you create any carbon dioxide then you're still able to do a little bit of the carbon cycle in order to try to put enough carbons together to create some sugar so this is just a mechanism to make sure that there's still something happening in order to get more energy kind of like in your body when you have like lactic acid when you're like working out that lactic acid burn is an aerobic cellular respiration but if you didn't do that you wouldn't have enough ATP to continue doing what you're doing and you probably died so it's just kind of like a crappy way to get the job done like worst comes to worst this is what we got to do sorry about it but at least we're gonna get the job done it's just it's gonna be quick and sloppy and it's not gonna feel nice that's essentially with happening here ok we talked about that so c4 plants minimize the cost of photorespiration by incorporating carbon dioxide into a 4 carbon compound so this is different because photorespiration usually does a two-carbon compound this is incorporating carbon dioxide into a four carbon compound okay so an enzyme and the mesophyll cells remember the mesophyll is the tissue that's in the middle of the leaves um has a high affinity for carbon dioxide and can fix carbon even when carbon dioxide concentrations are very very low so even if there's only a little bit of like residual carbon dioxide because the Semana are closed it can still be fixed okay these four carbon compounds are exported to bundle sheath cells where they release carbon dioxide that is then used in the calvin cycle okay so this is showing you the overall like representation of the process so you've a c4 plant and you have a cam plant so you have the mesophyll cells and you have our bundle sheath cells so like I said you're gonna be actually like sending it a little bit of carbon out carbon dioxide with organic acids here you're gonna be releasing carbon dioxide in order to go through the calvin cycle it's your produce sugar okay it's spatial separation in the steps because you have two different types of cells here you have like it's all happening in the same area its temporal separations of the steps temporal is talking about like times of the day we have night and date so we have carbon dioxide that's gonna be entering mixing with organic acids and in in order to put more carbon dioxide into the calvin cycle to create sugar this happens during the day here and then here this is happening at night so you'd have those stomata open that night when temperatures are typically a little bit cooler and then you'd close them during the daytime so you're just getting this carbon dioxide from other chemical reactions that are happening without further input of carbon dioxide from the atmosphere okay so cam plants which is these are just talked about okay so some plants including succulents or our camp plants they fix carbon a little bit differently so camp plants open up their stomata at night like I said when it's a little bit cooler incorporating carbon dioxide into organic acids the stomata closed during the daytime because it's very hot and they'll lose too much water and the plant will die that way and carbon dioxide is released from organic Syd's and then used in the calvin cycle so that's basically what I was just saying written out for you here and there's a visual representation of it again read it go back and look at the picture promise the pictures really do help you understand this overall process again spatial difference here because we have two different types of cells really the steps occurring in different cells and here we have it all occurring within the same cells but it's temporal separation because of the time of day okay so the importance of photosynthesis a review okay so the energy that's entering the chloroplast is sunlight it gets stored as chemical energy and organic compounds okay so we have the sunlight that's coming in at solar energy the point of photosynthesis is to turn that solar energy into chemical energy so sugar is made in the chloroplast it supplies chemical energy and carbon skeletons to synthesize the organic molecules of cells organic molecules are talking about the Kanak for molecules and things here you know carbohydrates we're making some carbohydrates right now in the process of photosynthesis so plants store excess sugar as starch remember that like humans store the extra sugar as glycogen okay that's like kind of like precursors like fat and stuff like that but glycogen is just a whole bunch of glucose repeating and that's what starches as well it's just a little bit different linkages so plants store excess sugar as starch in the chloroplast and in structures such as the roots tubers seeds and fruits in addition to food production photosynthesis releases oxygen in our atmosphere which is really important because that's what we need right it's not important for the plant but it's very important for us okay so this is the overall process that we just talked about so this they actually added in photosystem to the electron transport chain photosystem one electron transport chain here okay so we talked about the light reactions and how important it is to create these products I've been going to go into the Calvin cycle here to create that g3p which is going to be released to store energy or to be utilized as when two of them come together to make glucose okay that's gonna be one says sucrose exported it's it's glucose that's exported okay and then that rubp is the thing that we are going to attach the carbon dioxide to is it's coming into the Calvin cycle again right here in picture there's a little enzyme it's called Rubisco that is the most abundant enzyme probably on the planet because it's in every plant we need it right and there's a lot of plants cool deal so that's the overall process of photosynthesis oh my gosh should we do it we did it guys we finished it photosynthesis please I'm gonna smash this and like please don't have a seizure looking at all a billion and a half of these slides okay read this now read this make sure that those things make sense then go back through and look at all the pictures that I put in of the different steps okay that's like the same picture this make sure that you can explain this what is happening in each of these steps this one make sure that you go through and you read it what is happening in these steps why are these things important why where are these things going next why why is this happening okay then you need to make sure that you go through Calvin cycle is gonna be the next thing we just talked about the light okay beautiful cool cool cool okay here we go Calvin cycle read this look at the pictures make sure that this makes sense pause the video flip this make sure it all makes sense okay I promise I put all these pictures here for a reason just like your textbook company it prints all of these colored pictures for a lot of extra money for a reason okay thanks for bearing with me I know that this was a lot I promise you that the study guides and textbooks will help thank you have a great day

Channel: Science Edu-cate-tion

Views: 8,677

Rating: 4.9254661 out of 5

Keywords: photosynthesis, photosystem, photorespiration, chapter 8, biology in focus, campbell biology, dark reactions, calvin cycle, light reactions, electron transport chain, cam plants, c3 plants, c4 plants, autotrophs

Id: PJhVdgmz3SM

Length: 59min 18sec (3558 seconds)

Published: Sun Oct 27 2019