Photosynthesis Notes PDF

That as exothermic if you are by chemist okay or we're starting with energy and then we're doing a bunch of steps to release the energy out of that molecule and that's the energy that we use to make ATP Okay so total synthesis in many ways is just the reverse of that where we're taking little molecu...

That as exothermic if you are by chemist okay or we're starting with energy and then we're doing a bunch of steps to release the energy out of that molecule and that's the energy that we use to make ATP Okay so total synthesis in many ways is just the reverse of that where we're taking little molecules and building them back up into a bigger molecule so because it's the reverse of respiration where we take energy out we now have to put energy in to take those little molecules and make a bigger volume that energy comes from sunlight okay so essentially photosynthesis is an energy transformation process where we're taking energy from sunlight and we're turning it into chemical potential energy in the form of glucose okay so the energy to break the bonds here and form these bonds comes from sunlight so we're taking light energy and turning it into chemical energy that's essentially what photosynthesis is all about make sense so the goal or the purpose of photosynthesis why photosynthesis happens is first and foremost to make glucose or to synthesize Google that's the whole point why are we doing that well because plants also need a source of ATP and energy to do their functions so they also will perform cell respiration okay common misconception is that plants do photosynthesis but animals do respiration that's not entirely true plants also do respiration right they just don't do photosynthesis so anything other than a plant and some bacteria and fungi does not do photosynthesis but everything does respiration there's not a single living thing that does not do so respiration how are we making that glucose well we're making it by sticking a bunch of stuff onto carbon dioxide molecules so the carbon dioxide that the plant is absorbing out of the atmosphere is what ultimately becomes the sugar which kind of makes sense cuz if you remember from respiration the carbon in the sugar that we are breaking apart ends up as carbon dioxide so this is just a reverse of that and photosynthesis is another example of a redox reaction okay except here instead of oxidizing things we are reducing things nice so carbon dioxide is going to be reduced reduction remember is a gain of electrons where do those electrons come from they come from water and after you oxidize the water you are left with oxygen the oxygen that the plant releases as a waste product was initially part of the water law not part of the carbon dioxide hydrogens create a proton gradient we've got to that and then the leftover part is the oxygen that is released as and all of this is happening inside the chloroplast in a particular part called the thylakoid Lumen I'll get to that and then the energy to drive that process comes from light and then light is converted into ATP and another electron carrier called nadph no that is not a typo there are two there is nadh and nadph which one's which and one with the key is the one in photosynthesis weight okay I want you to think of photosynthesis the word photosynthesis as being a conjunction of two words photo and synthesis okay photo means light photography or taking a photograph and synthesis means to make so what are we doing we're making things using light okay but those two words in photosynthesis are actually happening separately independently so there's a section of photosynthesis related to light and a section of photosynthesis related to making things and they actually happen independently of each other okay so we have what are called the light dependent reactions the ones that depend on light being there that's the photo part and then the synthesis part is where we're making stuff but we don't actually need light for that stage so it's light independent okay so we're going to split photosynthesis into two parts very much like we split respiration into glycolysis transition crabs Etc okay photosynthesis is going to have light reactions and like independent reactions are commonly called the dark reactions even though they don't have to happen yeah that's an error it should be aqueous What's happening in those stages is we're using the energy from the sunlight the solar energy to make ATP and to make nadph okay don't have to worry too much about the structure of nadp Plus or nadph it has the same job as nadh it's an electron carrier so this is really just an energy transformation process this is the part where we're changing sunlight or light energy into chemical energy or chemical potential energy in the form of ATP and nadph Long as there is sunlight available this process is happening okay then now that we have this chemical potential energy as ATP and nadph in the light independent reactions or what are sometimes called the dark reaction we're going to use those molecules to reduce the carbon dioxide and turn it into glucose Just take place everybody all together I Answer to a grade 12 levels just like you're never going to say the PowerHouse of the cell to me ever again okay we're not going to save photosynthesis happens in the chloroplast anymore okay we're going to be more specific than that okay so in plants which are autotrophs which means they make their own food okay they all have food producing structures okay and those are in the leaf not surprisingly but not all of the structure of the leaf is involved in photosynthesis there are only certain parts okay so not all of the cells in a leaf actually have chloroplasts okay in fact many of them don't okay so in the leaves there's two major areas that photosynthesis is happening where there's the greatest concentration of chloroplasts okay and that is the mesophyll cell so there's two layers of that okay and then there was another important part for photosynthesis which is in the stoma I'll talk about those in a second okay we'll do that one after okay so the mesophyll cells in the leaf there's two types where the stars are okay there's what's called Palisade mesophil and then there is spongy mesophil okay those two plant tissues are where the photosynthesis is actually taking place okay and these cells are packed with chloroplasts because that's their job it's just to capture that sunlight in the light dependent reactions make ATP and nadph okay so this first Palisade mesophyll you can see his very dense they're packed really close together okay and they're very green they've got lots of chloroplasts in them okay they're also on the top surface on the leaf directly underneath the epidermis okay leaves have skin just like we do okay so there's a layer of skin the upper epidermis and right underneath that is the Palisade mesophil and that's where most of the photosynthesis is taking place okay why is it on the top because that's what's exposed to the most sunlight okay so they have a layer of protection from the outer environment and then lots of lots and lots of cells all performing photosynthesis okay underneath that is the spongy mesophil which is also cells that have lots of chloroplasts for photosynthesis okay but it's not as densely packed it's spongy there are air holes mixed throughout you can see it's not as packed closely together okay that's really important because we need to be able to have gases diffusing in and out oxygen carbon dioxide moving around okay and then we also have the transport system of the leak just like we have a circulatory system with veins and arteries and blood okay leaves have veins as well okay with types of tissues that are moving various things in and out of the leaf and exactly the same way as your circulatory system works and those Transport Systems are mixed in with the bungee medals so it's all kind of in the same area in fact the spongy mesophil is going to capture any sunlight that either goes through these cells and comes out the other side or misses them entirely okay so that we're getting as much of that sunlight captured as possible so that's where the photosynthesis is happening specifically the light reactions where we're using the sunlight to make ATP and nadph okay the other very important part of the photosynthesis process is we need to have the raw materials for the light independent reactions available too okay and one of those is carbon dioxide right we need to have the carbon dioxide there to react to stick things on to get the glucose production that we're looking for so we need to have carbon dioxide in these cells too okay and that Also linked to the environment outside the leaf through these tiny little ports is basically what they are they're little holes in the bottom of the leaf you can see them under a microscope okay and they can open and close to allow air to flow in and out of the leaf okay and those holes so the holes are called stoma is plural so Massa is singular okay and surrounding that hole in the leaf are two cells that are called guard cells and they kind of guard that opening in the bottom of the leaf and they are what allow the opening and closing of that core in the bottom of the week okay so this stoma or stomata are the gas exchange system that get the carbon dioxide into the leaf so that we can actually do the photosynthesis okay so this diagram here you can kind of see we're looking at it from the side so they kind of chopped the guard cells in half and you can see half of the poor okay another one here this diagram here is looking at it sort of head-on as if you were looking at the underside of the leaf okay so here's one guard cell they look kind of like kidney beans and one on the other side and then the stoma or the stomata is the hole that's in the middle and that would lead into the area of the leaf okay and they function just like pores do in that they are allowing gases to be exchanged between the plant and the atmosphere important for the plant are the carbon dioxide in water so we're trying to get carbon dioxide into the leaf and we're trying to get rid of the extra oxygen that's being produced because for a plant oxygen is a waste product we don't want that oxygen there we have to get rid of it okay unfortunately along with carbon dioxide and water we also can't control what's coming in and out it's literally just a hole in the leaf so water vapor will also move in and out of the leaf through those still not okay so the main purpose here is we're trying to get carbon dioxide in and water for storage and oxygen out but depending on the atmosphere conditions we can also have water vapor moving either in or out of the leaf as well right so on days like today where it's really humid okay perhaps water vapor is coming into the leaf that way but most of the time water is going to be leaving the plant tissues out of those pores in the leaf so don't plants also need oxygen for respiration they do but they produce excessively happening in the same place so photosynthesize in their stems okay but any of the Interior structures or the stuff Underground is respiration only so if we have a circulatory system that works effectively but we we have extra oxygen that we have to get rid of for sure does oxen do any harm or if it builds up it can be toxic not only to a plant but also to a human can have too much of a good thing thanks everyone we good okay okay so where specifically is this happening so we're not just going to say in the car flat but now we're going to zoom in on a chloroplast and look at what's happening where inside the chloroplasts okay so the first thing you may notice from the diagram is that there is a double membrane for the chloroplast where have we seen that before mitochondria right there are a lot of similarities between chloroplasts and mitochondria not surprisingly because they're involved in very similar processes okay so a chloroplast also has two membranes Folded up okay it's just a regular membrane the very inside of a chloroplast is filled with couple things but mostly were filled with lots and lots of stacks of these little love evil things that are called thylakoids okay so in the analogy here is talking about poker chips okay cuz it's the morning let's talk about pancakes instead okay so each pancake is a thylakoid okay and it also has a membrane so it looks like a flattened sack okay when you make a stack of pancakes that's called a granum or if you have lots of stacks it's called Grana g r a n a here and those stacks of pancakes are in a fluid kind of like cytoplasm okay but we're talking about the inside of the chloroplast here so that fluid is called stroma not stoma okay stoma or the holes in the leaf stroma is the fluid inside the corner and each one of those thylakoids each one of the pancakes or the poker chips has a space inside they're kind of a little bit Hollow and the inside Space is called the thylakoid space The light reactions capturing the sunlight and turning into nadph and ATP happens inside the thylakids I'm so where does photosynthesis happen inside the thylakoid membrane not inside the core of us better answer Dwight wants to know why are plants green Ria we can only see the color green because why you do you just you're trying to get the wording right yeah yeah okay you do but yeah that type of light and you only live like it doesn't absorbers of green so right plants are green because that's the only color of light that they don't use okay so when you see a color with your eyes what is happening is white light from the lights is hitting that thing right and then that color of light is being reflected off of it so that color of light hits your eyeballs and then your brain says that thing is red okay it's because only the red light is being reflected off okay so we have lots of different colors of light okay as part of the electromagnetic spectrum okay so when we're dealing with visible light it's a really small section you might remember from like grade 10 Optics okay and it all has to do with wavelength okay or how close together the peaks of the wave of light are so when they're really really far apart they're radio waves okay so if you're listening to the radio okay your radio is picking up very large wavelength like meters to kilometers per wavelength okay and that's what is transmitting the sound from the radio station okay you shorten that up then we have microwaves which you can use to heat up your lunch okay then we get even smaller wavelengths as infrared what we commonly describe as heat okay so heat is infrared radiation okay so if something is hot it is releasing this type of energy okay and you can feel that okay then we get into the parks that we can see so the red wavelengths have the largest wavelength they're also the lowest energy and then we go red orange yellow green blue indigo violet that much smaller wavelength much higher energy okay closer together and then after Violet we have ultraviolet which is just beyond Violet okay UV is the stuff that is coming through the atmosphere from the Sun and burns you okay and then if you add more energy and make it even smaller we get into x-rays you can see if you have broken bones okay and then we get even into really really small waves okay 10 to the minus six data meters and then we have gamma rays which hopefully you're never exposed to cuz they're nasty okay so when we're talking about sunlight but we're really talking about is different colors of visible light that carry different amounts of energy okay the more to the left it is the more energy it has and the more purple the color okay the less energy the more red okay so plants in particular carry not just one pigment they carry several pigments and a pigment is going to be something that is going to actually absorb those particular colors of light okay so when light hits something there's three things that can happen okay it can be absorbed it can be transmitted which means it just goes right through it and Carries On Through The Other Side think of like a window or it can be reflected that which means it bounces off and when we're looking at plants and leaves and things like that all three of those things happen okay so dealing with sunlight or colored light something like that some of it gets reflected some of it is absorbed as some of it is transmitted through just depends on the amount of each type Of the thylakoids in the chloroplast okay we'll talk about why that is in a second but essentially that's why plants are green because the green light is bouncing off the surface and it's coming back at you so when you're looking at it your eye is picking up that reflected light and your brain says that thing is green interestingly some of the green light is also transmitted through to the other side so if you're underneath the tree and you look up it also looks green okay and that's because some of the green light goes all the way through the leaf and comes out the other side okay the other colors the red orange yellow blue and violet they're the colors that get absorbed so that's why the color changes so that the leaf isn't white or black it's green because only certain colors are being absorbed and others are not yes just scream that's not correct oh what about sorry yeah Have you looked outside recently what color are the leaves red orange yellow brown right you got all kinds of colors going on right now so what's happening there okay we have lots of different pigments in leaves okay and in the fall okay the pigments are broken down by the plant to essentially recycle and save them for the next year okay the one that gets broken down the most and the earliest is the chlorophyll which is the green okay but there are other colors in the leaf all the time from other pigments carotenoids and sealantis and things like that and that's what makes it red and yellow and whatever so when you're looking at trees now that have colors what's happened is the chlorophyll has been broken down so it's not green anymore but the other colors haven't been broken down yet and that's why it looks yellow and red because those other pigments that were always there are now able to show through because the green is being broken down I'll show you inside okay so in leaves and plants in general we have lots of different pigments what is a pigment a pigment is a compound or a chemical that absorbs certain wavelengths of light while reflecting others it's the things that we use to make colors think of like paint as pigments in it okay so plants absorb light except for green and that's why plants look green because the green light is bounced off the plant or it goes right through it and comes out the other side and ultimately hits our eyeballs and then that's why we see it as green That's funny. down the teacher's wrong thing no they just simplified it I also told you that chlorophy was one thing the green For this course is made of two different chemicals we call them chlorophyll a and Chlorophyll B and the structure of the chlorophyll molecule itself allows it to trap sunlight or any light except green light okay so it does not absorb green light but it absorbs everything else and the reason there's two different ones is that there's better at different colors of life so chlorophyll a is better at certain wavelengths Chlorophyll B is better at other wavelengths so when you have them both kind of get the the vets of Both Worlds and you're able to trap more of that light energy so looking at all of these different pigments but we can do is we can shine a specific wavelength of light at this stuff and see how much of it is absorbed and how much of it is reflected back and then we can collect that data and then we can graph it to make what's called an absorption spectra so it's a graph and it shows the wavelength of light and how much gets absorbed okay and it looks like this okay so this is a graph we've got different wavelengths of light across the bottom to Red Light very large wavelength Violet very short wavelength and then on the y-axis is how much of that light is being trapped okay and they've done that for a couple different pigments so here's chlorophyll a and Chlorophyll B they've also done the carotenoids which are a separate group of pigment that are kind of orangey yellow in color okay and then there are other ones too that just aren't on this graph okay but you can see that different chlorophylls absorb different wavelengths of life so chlorophyll a is really good at getting the violets and the Blues okay and then also again at getting the really dark Reds okay and in the middle we got a lot of nothing okay Chlorophyll B okay is better at more of the lighter greens okay or sorry the lighter blues and into the very edge of the greens okay and then again in the orange area so when you put those together we're absorbing this light we're absorbing this light okay with the carotenoids we can get some of the darker greens a little bit okay and then we have this big block here where we're not absorbing any of it okay so what color is there the yellows and the greens and those are the colors that we see because those are the colors that are not being absorbed okay and then again we get more absorbance again in the red areas all right so if you take those colors out of the full spectrum what are you left with your left with green and that's why plants are free okay this isn't complete there are other pigments as well that especially deal with this area over here but in general very little absorbance around the 585-90 area and that is the color that just happens to be green make sense okay so essentially when you look at this graph the higher the line the more of that light is being absorbed and the left of it you would see okay how does that work well this is what the chlorophyll molecule actually looks like okay it resembles quite a bit of hemoglobin or the heating group in hemoglobin except instead of iron in your blood okay plants have magnesium in their chlorophyll okay so magnesium is a really important vitamin or mineral to plants so they have to have enough magnesium so when you are gardening or your adding stuff to your soil Hydrocarbons yeah there's a big long chain of hydrocarbons isn't there okay and when you have a big long chain of hard carbons like that what properties does it tend to have right it's going to be nonpolar right it's it's kind of like an oil right it likes being in hydrophobic environments such as the inside of a membrane okay so this part of the molecule is kind of like the anchor that hold the molecule in the membrane and then this part sticks out above the membrane because it's not in the memory cuz it's polar right look we've got we've got some oxygen if it's chlorophy it's got double bonds we've got some nitrogens in there so we're going to have some polar functional groups here means it does not want to be in a membrane okay and it kind of has this sort of large surface area it looks a little bit like a satellite dish okay and that's precisely what it's supposed to do this is the area of the molecule that is collecting the sunlight so it has this big wide open structure to catch as much sunlight as it can and this is the anchor that's holding it in place make sense okay the difference between chlorophyll a and Chlorophyll B by the way is one small change here okay it's either going to be a double bonded oxygen or it's a methyl group that's the only difference between the two and that small little change impacts the color of light that it can afford okay you don't need to know that structure just know that it has magnesium in it and it has this big light capturing section and a tail that anchors it in the membrane okay so as I mentioned there are lots of other pigments these are the ones that we can see in the fall like now okay so red and yellow and orange those kind of leaves what's happening there is the chlorophyll has been broken down by the plant okay to save until the spring and then when the green is gone because we broke it down the other colors start showing up from underneath they were there the whole time we just couldn't see them okay so we have carotenoids which are like yellow orange think of carrots okay there's xanthophils which are also kind of a yellow color and then there are anthocyanins which are red okay you don't really need to know this it's more for interest sake it's usually what happens as well the leaves aren't always green what's happening there so these other pigments are there all the time okay and if you look in general we're dealing with the Reds and the oranges in the yellows which going back to this they're not shown on this graph but what are they absorbing all this stuff okay so we capture as much of this light as we do as this light we just need a different pigment to do that okay makes sense you don't need to know most of this Go back to the late 1800s when the scientist named Engelman and what he did was he first of all shined life through a prism to break it apart into its wavelengths and then he put a tank that was filled with fluid and then also a type of bacteria that is able to photosynthesize okay so plants are the only things that can do photosynthesis so I'm bacteria can there's some fun guy and algae and other things like that I can as well okay well the important thing about these ones is that he's bacteria can move inside this liquid they can swim around and what he found was when he left that tank with the bacteria in it exposed to the different colors of light what happened was they started producing oxygen but only in this area and this area okay and none in the middle okay so that is telling him that okay well where is the photosynthesis happening well with the blue and the purple light and the red and the orange light but we're not getting any Oxygen production in the middle cuz we're not able to use the green light so then what happened is those bacteria they actually moved away from the green so that they were able to survive as a result of that so what was the result of this experiment we know that photosynthesis produces oxygen and that it's only being produced from those particular wavelengths of light so we get the highest amount of photosynthesis from blue light and red light and a lot less from Green Light cool that's it for today With one of the hydrogens bank and System rate this molecule apart requires energy and not energy comes from right okay so that's kind of a general summary and then we'll dive into it a little bit more Dividing into two steps as we talked about so in the first light reaction what we're looking at today we're capturing the light energy and then we're using that energy to break apart water and ultimately transfer that energy into chemical energy chemical energy isn't going to be in the form of ATP and nadph which are carrying those high energy electrons to The Next Step where we start making molecules First thing we have to do in the light reactions is we have to capture the sunlight and for that we are using the chlorophyll that we talked about yesterday okay so chlorophyll is the main pigment pigments or two of them that are absorbing the incoming light but as we talked about yesterday there are other what we call accessory pigments that help okay but the main character is chlorophyll and the chlorophyll has that nonpolar tail that is anchored into the thylakoid membrane the membrane of the thylakoid which is that pancake or poker chip that big antenna structure that I showed you yesterday is called the porphyrin ring you don't need to know that I'm not going to ask you that okay but in case you're curious that big thing that collects the light that's what it's called and it has magnesium in the middle that is important you the middle is non hydrophobic right like like Globs forof oil in waterneed to know that so the membrane is hydrophoib inside of thec ismiddle hyd so this part is also nonpolar so it sticks togetherRemember so just to show you that structure again it looks like this thanks thanks kind of a very wide sort of satellite dish structure that's where the light is being absorbed okay and then this is the hydrocarbon tail that is anchoring it into that memory okay when there are men Anchored In The Membrane they kind of cluster together so you get a lot of chlorophylls all in one kind of unit and then there'll be another unit of a whole bunch over here and things like that and that's important and I'll talk about why that is in this so to answer your question cut I hear that double memory with the hydrophobic tails in the middle so this part literally anchors into this area what's holding it there is it doesn't want to be in water these don't want to be in water so they hang up together and then any of the water or pull their stuff would be under a bumper below everything in the upper part I'll pull it like this I mean not each individual thing but when you look at it as a collective it's Fuller so you answer to the middle right next to the surface with that wide open structure to capture the light what is it can I go page back I sure can hold that thought How does it actually absorb the light well let's look at how Okay so the pigment or any of the other ones it doesn't absorb the light on its own so I showed you how they're kind of clustered together right they work as a unit to collect the light so each one of these little discs is one of the the top parts of a chlorophyll molecules so there's one there's one there's one so we've got three seven 13 chlorophyll molecules embedded in the membrane in this diagram and then there's other accessory pigments the yellows and the red what we talked about okay and they're arranged in this structure so that they can actually pass the photons of energy from one chlorophyll to the next to the next to the next okay and one of them is going to be much more important than the other one is it's called the reaction Center in this one it's a little bit darker green and then all of the other ones okay form What's called the antenna complex so if you think of like a satellite dish okay the reaction Center is the one that's right in the middle okay so all the ones around the outside they kind of funnel the energy towards the one in the middle and that's the same thing that's happening here so in this diagram when you can see is all of these chlorophylls are able to absorb light and when the light comes in what it does is it excites electrons to a much higher energy state so the electrons jump up energy levels think of like remember like orbits around an atom from like grade 10 okay so instead of being in the the closest circles to the nucleus the electrons jump up many levels to be a much higher energy level because they just got hit with this light energy those high energy electrons they kind of Bounce Around the antenna system and eventually they will hit the reaction Center chlorophyll and the reaction Center is going to grab those high energy electrons and pass them on to the first electron acceptor which I will talk about that's about energy excites the electrons not electrons jump from different chlorophylls to the reaction Center which is also a chlorophyll yes and then the reactions happen The antenna complex is going to absorb the photons of light and it transfers the energy from the photon to the reaction Center that darker green chlorophyll okay that darker green one has to make chlorophyll a not Chlorophyll B and then they pass that energy on to the first electron acceptor It looks a bit like this okay so I hear you have the collection of chlorophyll molecules embedded in the thylakoid membrane correct so the photon of light or the particle of light comes in it gets bounced around inside those different chlorophyll molecules and eventually it gets to the reaction Center where it excites electrons so they jump up to a much higher energy level so these are like low energy electrons much higher energy electrons and when they're in that excited state they get past to an electron acceptor talking about that part later on so the electrons in the other chlorophyll like don't get excited right it's only the one in the reaction Center they do but they get temporarily passed on to like electrons here can get excited but then they're going to bump into some of those ones in the past that energy along so we're passing the energy until we get to these ones because these electrons jump up and then they go somewhere else they don't come back to this photo system as you'll see so once that happens this reaction Center chlorophyll is now missing electrons because they've disappeared somewhere else so as you'll see the second part of this light reaction is we have to replace those electrons that have now left hold that thought so essentially the electrons and antenna complex they just kind of bump into each other and get thrown back to their original where they were basically and the energy gets somehow transferred to the center or the reaction Center think of it like it's just collecting all of that sunlight so like each other is going to be doing that but there's tons and tons of photons that are hitting this thing all at the same time so one from here one over here one here when you were here and they're all kind of bouncing around but they all get to hear and then they go up so it kind of just funnels everything into that one chlorophyte molecule that is now missing electron okay we'll get to that so this is how that happens okay so electrons are normally in their regular States called their ground state they're just chilling okay and when the photon hits the chlorophyll they get zapped with energy okay and when they get Zach with energy they jump up to higher energy levels right they're moving around a lot more they're excited okay this happens to all substances Okay so the pavement outside also gets hit with photons and the electrons in the pavement also get excited the difference is they will eventually drop back down to their lower energy level and that energy is then released usually as heat that's what makes pavement hot in the summer at least okay but in this system it isn't released as heat because those electrons get passed on to this special electron acceptor and since the electrons are not going back to where they started it's called noncyclic electron flow right so we could have electrons going back to where they started in a circle that's cyclic electron flow in this case they're being excited and then they're going somewhere else so it's noncyclic electron tool that is an important term So you went like not with these like cuz these are LEDs but fluorescent lights essentially how they work is when the electrons drop back down to their initial state they release light to get rid of that energy instead of heat and that's what fluorescent means think of like one of those two lights with electrical connection at each end when the electricity goes through that too that's what's providing the energy to excite the electrons so you get all kinds of electrons in all the different atoms inside here which could be made of a variety of different things let's say Neon it's kind of the one that sticks the most okay and when the electricity edges those those electrons jump up to higher energy levels okay so they're very excited okay but there's nowhere for them to go right they can't be passed on to something else So eventually they drop back down and when they drop back down to that lower energy level they have to release that extra energy and they do that in the form of light and that's how fluorescent lights create lights I mean electrons are always moving so yes they do move but like they're not moving from one place to another they're just getting more energy and then when they drop back down is when they release the light interestingly the light that they released is actually UV and then the edge of this the last two is coated with a substance that absorb some of that energy and it changes the UV light into white light so that's why those tubes are always white if they were clear it would be UV light coming out so they coat it in what's called phosphora to release that the light as white light instead of UV light again okay so does this make sense okay so the light is coming in it's citing the electrons those electrons they fire around inside that photo system eventually they get to the reClick electron flow when the electronsaction Center those electrons get excited and then instead of dropping back down they get past on to the primary electron acceptor which we'll talk about in a second and then they keep going we never see those electrons again so that's called non-cyclic electron flow because they're not going back to where they started they go somewhere else yes can you go back to that no this one just Those collections of the chlorophylls right that is called a photosystem and there are two different types of them photosystem 1 and photosystem 2 they do work together but one of them is also able to work by itself okay and their name photosystem one and two in order of their discovery not in order of use so we actually use photosystem too before we use photosystem one in we don't do anything but yeah I don't know just test okay so nothing tomorrow Monday we're doing the dark reactions by time to write we should have done that today cuz Diwali so light reactions and then we have a lab to do so that will be Tuesday Wednesday so Happy next week do you have to move on Photosystem one and photosystem 2 you'll see them in a moment okay why are they different they actually absorbed like different wavelengths of light okay so there's sometimes called P 680 for the total system that absorbs 680 nanometers of lights or p700 we're going to call them one and two that's photosystem 2 or p680 okay so one way flow of electrons and energy we excite the electrons we pass them on and then we never see them again and as I mentioned if we never see them again that reaction Center is now missing electrons that it just gave away so it has to replace the ones that it just lost so where do those electrons come from they come from water okay so when we Will be waste and the hydrogen part of the water although we've already used the electron so it's just protons left at this point they get attached to nadp to make nadph so the energy is actually being used to split water that's ultimately What's Happening Here Okay so let me just kind of explain this diagram this gray and yellow thing okay that's the membrane of the thylakoid okay so we're inside the chloroplast this is one of those pancakes or poker chips or discs right and we'd have a whole stack of these like this okay so the photo system with all of the chloroplasts part of me chlorophyll is embedded in this membrane okay so at the top of this that's where all those light collecting antenna are and in this case we're dealing with photo system too which is this one okay there are lots of these embedded throughout it's not like it's set up in one big long chain crack so they'll be lots and lots and lots of bees inside the membrane okay so the light hits that okay that funnels around the beginning and then we excite the electrons from the reaction Center okay those electrons follow this arrow to the first electron acceptor okay and then eventually they move further we'll get to that okay water that's inside the middle of the thylakoid okay it gets split apart okay the oxygen will stay there the electrons are going to replace the electrons that were locked from here so that's what this little arrow is these electrons are replacing the ones that were there okay and then the H's are going to end up being attached to nadph overall so they're just going to float around in here for a while first that's why we have a high H+ concentration okay and then eventually they're going to end up here but we'll get for that part or just looking at this right now okay so photosystem 2 light comes in it excites the electrons they leave back water gets broken apart to replace the electrons that were lost oxygen and H+ are left over good is what are you using the same energy as like the one you stay inside the electrons is what are using the same energy as the one being used to excite the electrons to split yes Where do they go they go through another electron transport chain and difference but it works the same way okay and they travel from photosystem to two photosystem 1 okay so there's a bunch of proteins embedded in the membrane in order they are also in order through electronegativity so that one pulls the electrons from the next one it works exactly the same as the Etc in respiration it's just different protein you don't need to know the names and just like in respiration when those electrons pass from one to the next we pump protons across the membrane it's the exact same process just with different proteins that creates the concentration gradient So now we're in this park that's why it's a liger color right now we're here so the electrons are being passed from one protein to the next to the next eventually they go to photosystem one every time they get past we get some protons coming from outside the thylakoid okay in the stroma into the middle of the thylakoid so we get a very very low PH inside lots of H+ around okay why do we want that for the same reason we wanted in respiration we're going to use it to make ATP eventually okay so every time we pass these electrons more protons come in on top of the ones that we already got from the water okay and then eventually those electrons get past the photo system okay yep the proteins are in the membrane just like the Etc in the mitochondria yeah cuz more being pumped in so it's not higher age plus means lower pH right acids? Those electrons all the way to photosystem 1 when they get to photosystem 1 they don't have any energy anymore because we use the energy to pump those protons across so now they're just regular old electrons but photosystem 1 also absorbs light so we can excite them again Total system 2 the electrons in the reaction Center are the ones that get excited and then we have to replace them okay these ones were not replacing with water we're replacing with the electrons that came from photosystem too Which is a protein that takes the high energy electrons off of the photosystem it's a different one than photo system 2 but it's doing the same thing Both parts are important and you'll see why okay so now we're looking at this section okay so those electrons got passed down passed down okay you get to photosystem one the reaction Center also gets hit with light those electrons jump up and they get passed to a different primary electron acceptor okay so we have to replace those electrons but we use the ones that we already got from the other photosystem so we're not using more water right the electrons are coming from photosystem 2 into photosystem one to replace the ones that are going this way okay that requires more light to excite them again but it doesn't require new electron we already have the electrons we need you just have to give them more energy okay once they have more energy they get passed down more of the electron transport chain as you'll see except now we're not using them for H+ we're going to use them to make nadph We end up at the very last one is called nadp reductase what do you think reductase does it reduces what does it reduce nabp and ADP and it ends in ASE so we know it's an enzyme so this is an enzyme that reduces nadp okay names of enzymes are generally logical okay so those excited electrons get past on to this protein and ultimately they reduce the nadp molecule to make nadph why do we need nadph well it's going to carry those high energy electrons to the dark reactions that will talk about next week That's all we really excited the same electrons that we had before we passed them on to a protein called paradoxum you don't need to know that and it passes them on to nadp plus reductase so we have nadp floating around inside the car blast it's going to get reduced okay with the electrons and some H+ to form nadph and then this molecule is going to end up being used in the other part of the chloroplast the stroma for the light independent reactions or the dark reactions which is called the Calvin cycle that's next week okay and then the other leftover bit that we have is remember we have this H+ concentration inside so we're going to use literally the exact same protein that we did in respiration okay we're going to let those protons back out and we're going to make ATP with it okay so photosynthesis in the light reactions is making both ATP and nadph okay they serve different purposes this is providing the electrons to be able to reduce the carbon dioxide molecule and this is providing the energy for that reaction so we need both yes so it's the same thing no difference right and then we can just recycle the same protons over and over again so if you remember how ATP synthase works from respiration you also know how it worked for full since this cuz it's literally the same okay now we talked about substrate level phosphorylation and oxidative in photosynthesis it's called photo phosphorylation because we're using the light to phosphorylate the ADP to make ATP okay other than that it's literally exactly the same You should know the ratio four protons per ATP everything else you already learned last week So photosystem 2 is where we start light comes in it excites some electrons those electrons get passed down the Etc okay we replace those electrons using electrons from water okay so that photosystem 2 doesn't run out of electrons okay the oxygen and the H+ stays in the middle the electrons move down as they're moving down we get more H+ into the middle and eventually we get to photosystem one okay same electrons now we're going to zap them with light again give them more energy and then we get past them down again to be able to make nadph can't using those electrons and H+ that's just around okay that makes nadph and it gives us this proton gradient okay the nadph we're going to use on Monday okay and we can make one ATP molecule for every set of electrons that go through the whole thing the problem is when we get to the dark reaction we don't need these in equal amounts we need more ATP than nadph so I need to have another strategy to make just ATP and not nadph okay so that I can make up the difference cuz I don't have enough ATP that what I just described for you is often called the Z scheme because the Zed is the shape of the electrons as they go through the system in terms of their energy so if you turn the Z sideways it looks like this okay so we start with photosystem too we jump up electrons with energy that's the top of the Zed then they slowly come down the back of his head as we move those protons across and then we jump them back up again okay so it makes us dead cracked that strategy gives us equal amounts of ATP and nadph hold on okay but we need more nadp or sorry more ATP than nadph so using just photo system one we can create a cyclic electron flow that will only make ATP to make up the difference so we have non-cyclic electron flows that scheme and we have cyclic electron flow noncyclic makes both ATP and nadph cyclic makes only ATP Difference is we already have all the parts that we need it's just where the electrons go after they've been excited in photosystem 1 okay so they're going to get past the Paradox in and then from there we can either go to nadp reductase or we can go backwards to the cytochrome complex and then let more protons through to make another ATP okay so just to back up a little bit so Zed scheme would be up going down the back of the Zed up and cyclic flow we start at photosystem one we passed the paradoxin and then instead of going this way now we're going to pass them to here and then we just go around and around and around around we can use the same electrons over and over again which is why it's cyclic and since we're doing this way we pump protons across and we keep getting more and more protons to make me pee only okay so in words cyclic photophosphorylation only uses photosystem 1 and we are only generating ATP we are not making nadph we are not using water we are not generating oxygen waste or just making ATP? Passed around eventually we get to p680 psyche electrons okay those electrons get replaced from water to get oxygen proton whatever those electrons get passed down this process which is making ATP because we're pumping profile Get passed to FD which is paradox and you don't need to know that and then now we have a choice okay if I have enough ATP then I'll just keep going this way to make nadph but if I need more ATP from here we're going to pass them back here and make more ATP and just go around this way okay and we can keep doing that literally forever as long as there's light right and then once we have a lot of ATP then we can send it this way again and make more nadph so does it just travel through the memory it's one of the proteins in the electron transportation but they don't cuz you know we use oxygen for the other one is more electronegative than the p700 but it's less electronegative than both nadp reductase and cytochromeo But that's what we need the light for we have to rip the electrons off the oxygen molecule using energy that energy is the light energy that we're done to make that process not sense right Photosynthesis The Details Part 2 To actually making it Google we haven't done that yet always done so far as we took water and he was supposed to apart we got rid of the oxygen he kept the electrons by sticking them onto nadp plus okay and we kept the hydrogens partially for that and parsley for our proton gradient so that we have lots of ATP present okay so at the end of the light reactions and these are the products that we have made that we're now going to work with for the next step which is called the light independent reactions or sometimes called the dark reaction okay light independent is a better term because they don't necessarily happen in the dark they can happen in the dark but I also happen during the day as well some plants will separate them by time as you'll see when we get there other plans don't but it just means that we don't need light for this part okay we have everything we need in the ATP the nadph and then the carbon dioxide that we're going to bring in through those pores in the league okay so that's kind of where we left off with before so now we're going to focus on this part how do I take carbon dioxide and turn it into sugar cool all right okay so the biggest part of this is called the Kelvin cycle it was also discovered by another dead white guy and he also won the Nobel Prize for it okay most important part of this is that it's happening in the stroma of the chloroplast okay so we're not in the pancakes anymore or now in the liquid that's kind of like cytoplasm but it's still inside the chloroplast it's just not inside the rear discs okay okay so we're in the stroma and what we're going to do is we're going to use that ATP and the nadph that we already created using light to basically make glucose from carbon dioxide okay which obviously is going to require a lot of energy it's not a spontaneous thing we're taking a small molecule and making it bigger so we have to fight against entropy if you remember that term and we also have to fight against enthalpy as well okay so this is an uphill battle which is why we need these supplies to get us there okay so this is not something that would happen on its own we have to sort of put in some effort to make it take place please I can figure it is all right now. you take a small CO2 right and then you have to make it into a like a sugar right cuz that's why we have to use because like it just overall you're going up the volume okay and is also going against entropy okay but we don't need Use the light at this point we could do this in the dark if we want it we have all the stuff that we need already okay so just like the Krebs cycle we're going to start with one thing and then we're going to go around the clock face and then we're going to end up right back where we started okay the difference is this one is split into three different stages or phases had the first one's called carbon fixation then we have a bunch of production reactions and then we're going to regenerate this thing called rubp I'm going to talk about that okay so phase one first thing that has to happen is we need to get the carbon dioxide into the plant so that's going to happen first through the holes in the leaf those pores called stoma Going to bring the carbon dioxide into that airspace inside the leaf itself and then we're going to grab that carbon dioxide and bring it physically into the cells and into the mitochondria and just like we phosphorylated glucose to make it stay inside the cell we need to do something with the carbon dioxide to make it stay there as well so we're going to attach it onto another molecule called rubp hey are you VP stands for ribulosis phosphate you do not need to remember that rubp is more than okay so we grab carbon dioxide and we stick it on to this other molecule and not makes it stay inside the chloroplast can't escape Carbon dioxide onto rubt we're going to make an unstable molecule okay it's not going to stick around very long because it is unstable so once we stick enough carbon dioxide what happens is it splits in half okay and the name of the molecule it splits into is called PGA or phosphoglycerate and we're going to get two of them right cuz we're starting with one six carbon unstable thing and it splits in half into three carbon mullings yeah okay It's a weirdly named enzyme it is also the most abundant enzyme in the world why a lot okay because every single plant uses that to get carbon dioxide out of the air and into the plant You're like how come we're getting six of them what's happening there okay so graphically we're starting with a five carbon molecule 5c we have three of them so that's 15 carbons in total okay we're going to add three carbon dioxide to that one to each one okay which would make three six carbon molecules but then they split apart so eat six carbon molecule forms two three carbon molecules so instead of having six or instead of having three we get six okay so 6 * 3 is 18 15 + 3 is 18 it's still the right number of carbons okay so we're starting with rubp has five carbons in it each one of them grabs one carbon dioxide to make a six carbon molecule but that almost instantly falls apart into two three carbon molecules okay and we started with three of those we get six of those all right so nope that were taking three of these in at once okay so when we talked about Krebs cycle we talked about one acetyl-coa coming in and then the cycle going around once and then again for the second one this one we're doing three at the same time okay so that's because we need three of them to go around to eventually make enough glucose as you'll see better yeah are six p That's step one okay so now we have carbon trapped inside the chloroplast that's called carbon fixation stage 2 is now we're going to go through those reduction reactions and this is where we're going to use up that ATP and the nadph through those reduction reactions Okay so those six molecules of PGA they're going to get phosphorylated how do they do that we're going to break apart the atps that we made before okay to make one three BPG or bisphosphoglycerate just means it has two phosphates on it okay and then we're going to reduce them using the nadph that we made before okay and ultimately we end up with this molecule called g3p and just to make it fun they sometimes call it pig out we're going to use G Street feet answer all the high three phosphate out of those six molecules that are made one of them exits as the product and then the other five go around the cycle again it's easier when we get to the pictures Helpful than the words back so what we're doing is we're taking those three pga's each one of them is going to get a phosphate or sorry six each one gets a phosphate attached to it that comes from ATP so we're going to burn up 6 atp's one for each molecule it always has one phosphate on it so we're adding a second one so now it's dye hospital or bisphosphoglycerate one on carbon 1 on carbon 3 okay that molecule then gets reduced using nadph the electron carrier we made before okay and that is going to change this molecule into lesser all the high three phosphate or cheap three teeth we're not changing the number of carbons we're not doing anything else all we're doing is we're adding a phosphate okay in order to reduce the molecule which changes the orientation of all of the bonds and things like that okay and then not phosphate is gone again so we add it and then it's gone in the next step because it's just being used to take this molecule to make them okay it doesn't stick around long this molecule still has one phosphate attached but the other one that we just added is now gone now out of these six molecules one of them is going to exit the cycle that we can use to make sure fatty acids whatever we want and the other five are going to stay there so that we can remake this so that we can keep going around recycle the other five okay so three carbons come in and three carbons come out okay but here they were coming in as three separate molecules here they're leaving as one thing all stuck together okay so what the Calvin cycle is really doing is it's taking three carbon dioxide in it's sticking them together and then spitting them out the other end okay it's not the same carbon atoms but that's generally what's happening okay so now we've got our products okay so the last the rest of this cycle is just the recycling part how do I get the remaining five of these to turn back into this okay so the product that we're getting out of the Calvin cycle is G3 people through high three phosphate can we get one remaining can you repeat the last thing out of the Calvin cycle we already have our product now yep product that we're getting is one molecule of G3 feet yeah right so now we're going to go into phase 3 which is recycling or regenerating that r u d e molecule okay so to do that we need more ATP It's what makes the requirements for this different levels of ATP and nadph so up till this point we use the same amount of both we use 6 ATP and we use six nadph okay which you remember is what we can generate from the Zeds team or the noncyclic electron flow from Thursday okay but since we need more ATP these are the ones this is why we have to do that cyclic flow sometimes because we need more ATP than we do nadph I'll review that in a minute okay so these three ATP are going to be used to rearrange those leftover 5G 3 piece to turn them back into rubp happens twice like happens two times like for each like acetyl if you want to make a glucose this would also have to have to happen twice right so far we've got a three carbon g3po right so do we need glucose or are we happy with you depends right just like what happens to pyruvate depends what happens to g3p depends it depends on the need of the plant in that particular moment so if it doesn't need that extra energy it would just stick with the g3p like a phone at 2G through piece whatever the process is to make glucose if it's just okay so here's that one g3p that we got out we can do that with whatever we want we can turn it into glucose we can make fatty acids with it we can make amino acids with it it really depends on what the plant needs okay so this molecule is being produced is versatile I can do a bunch of different things with it right very much like as we were just saying the products what we do with that pyruvate in metabolism depends on what we need in that particular moment right do I need lots of ATP okay we got to keep breaking it down if I have lots of ATP maybe I'm going to turn it into fat instead it's a versatile molecule this is also a versatile molecule that's an advantage right because we're not forced to turn this into glucose if we don't need it okay so the plant can side what it wants to do with that Molly so flexibility is a good thing Okay so we've removed one we have five left over okay from those five okay we're going to use ATP to stick them back together okay so we had five molecules of a three carbon thing we had 15 carbons in total we're going to use some ATP and rearrange them into three molecules of a five carbon tank so they're still 15 carbons 15 carbons 15 carbons we just shuffle them around yes is that are those two ones the same thing they're different right the addition they're different Okay so what we do the first thing we do here is we take five three carbon molecules and we turn them into three five carbon molecules right we don't need to know the mechanics of that just know that we take them and stick them together okay that creates something called rubulos five phosphate as a phosphate on carpet number five and since we have three of them now we're going to use one ATP for each one so that there's two phosphates on each one and that makes rubp which is then you can go around because okay so what do I have to put into this okay carbon dioxide okay 9 ATP and only six nadph so then the requirements of ATP and nadph are different and that's why Hello just to make ATP so that I have nine atps and only six nadph's as needed I don't want to make more nadphs if I'm not going to need them right so waste food. so take away from this what goes in three of those nine of those six of those what comes out one of those okay and then if you want to make one glucose this has to happen twice right easy way to think about that is glucose has six carbons in it if three carbons are going in I have to do it twice to get six cards okay so just like crabs happens twice Calvin cycle happens nor reduce reactions so this molecule is getting oxidized this molecule is getting reduced lots of numbers for a Monday morning okay you might find this diagram helpful it's more or less the same thing but the difference is you can see the carbon things okay so this is a five carbon molecule 1 2 3 4 5 with two phosphates one at each end that's our ubp okay I add three carbons to it they almost immediately split in half so I end up with six three carbon molecules each with a phosphate okay then I'm going to add a second phosphate so there's one on each end okay and if I do that to six molecules I must need six atps to do that one for each one okay then this molecule now I'm going to reduce it okay by oxidizing this that's going to remove that phosphate that we just stuck on but we stuck it on there so that we can use the energy for that redox reaction to take place why did that happen At six three carbon molecules which we already had but now they have less phosphate okay this is a bit of an oversimplification cuz it's only showing you the carbons we are rearranging the other atoms here okay specifically oxygen okay so one of them comes out that we can do whatever we want with the five of them stay in okay we're going to do recombine them so two and a half of them check and then we're going to remake this rubp molecule okay that requires more ATP so that's why we need the different amounts of each one okay so three steps bring it in stick it onto ruvp to make PGA redox reactions to actually get the product that we want and then the recycling phase to get us back to where we started As I mentioned different plants will separate the light dependent and light independent reactions differently okay don't worry if you don't have this thing it's like a couple slides and I'm going to tell you what's important okay so we call different plants you put them into three different groups based on how they do the light independent reactions okay so the way that I just taught you okay we're going to take in the Calvin cycle we add the three carbon monoxide and we end up with a three carbon molecule PGA has three carbons in it because of that they're called C3 plants three carbons okay that's using that enzyme rubisco that I talked about we're adding carbon dioxide onto rubp it pretty much falls apart right away okay and we end up with six of them but there's three carbon molecules that are produced okay lots of plants work this way just fine okay common agriculture ones rice wheat soybeans pretty successful crops worldwide okay however they all kind of live in similar not totally the same but similar environments importantly it's not too hot where these plants live yes yes so they undergo the same cycle but just the product exactly how we just talked about it but the products the product is PGA Great if you live in that kind of an environment where rights wheat soybeans and other similar plants live however not all plants live in that environment we also have plans that live in the desert we have plants that live in the rainforest and when you live in slightly different environmental conditions something bad happens to Risco and the problem is that when it's really hot and dry a plant has to close those pores in order to stop itself from dehydrating to death okay if I leave those stoma open yes carbon dioxide is coming in that's all great except I'm also losing water vapor rapidly through the leaves okay and dehydrated wilts and it dies okay so in order to maintain life and self-preservation I need to shut all those holes in the middle of the daytime so that I don't die but as soon as I close those holes I'm not getting enough carbon dioxide anymore so the Calvin cycle shut down because there isn't enough carbon dioxide around to keep it going other thing that happens is start getting lots of oxygen inside the leaf still doing the light reactions we're still breaking apart the water to make oxygen so now suddenly inside the leaf I have lots of oxygen and very little carbon dioxide this is not a great situation if you are a plant it's the equivalent of putting you in a room with lots of carbon dioxide and very little oxygen bad things will happen on top of that rubisco the enzyme is a little bit sneaky in that not only will it grab carbon dioxide sometimes it also grabs oxygen and it's going to start sticking oxygen onto rubp instead of carbon dioxide kind of like carbon monoxide poisoning that makes that rubp molecule wasted can't do anything with it now cuz it has oxygen attached to it instead of carbon dioxide this process is called photo respiration and it's bad news for a plant okay so this will happen only during the daytime because the light is being used to break apart the water so we get lots of oxygen and that's the problem is we have too much oxygen inside the plant if it was dark we wouldn't be making any more oxygen cuz we can't split the water molecules anymore so this wouldn't happen so photo respiration cuz light is needed for this place but bad news otherwise because instead of doing what it's supposed to do Nabisco is not doing its job and it's actually poisoning us instead and not problem stems back to the environment it's really hot and really dry this happens so as you can imagine this is not really a good thing if you're a plant so we need to try to find a way to prevent this from happening and there are two different strategies that plants use to avoid photo respiration okay the first one They're explosive plants the difference is that instead of making a three carbon molecule in the first carbon fixation step we're going to make a four carbon molecule instead and since we're making a different molecule with also use a different enzyme which means rubisco is not involved and if we're this goes not there then there's no photo respiration Does is it's going to keep its stomata open during the day but it's going to be much more efficient at getting that carbon dioxide in and it also keeps the oxygen away from the rubisco enzyme and it does that by having them separate cells entirely okay so the leaves of C4 plants look different God because and the strategy herethey have different Anatomy okay so C4 plants instead of just having the mesophyll cells that we talked about when I first showed you the structure of the leaf they also have these other cells called bundle sheet cells and why that matters as you'll see don't worry about the details of all that is the mesophyll cells the ones that are next to those air spaces they don't have rubisco in them the robisco is in the bundle she stealth instead so they're physically separated into different areas okay these cells don't have the rubp and they don't have rubisco right that happens all down here so instead what we're going to do is we're going to bring that carbon dioxide in we're going to turn it into a different molecule that has four carbons in it don't worry about this I'm never going to ask you that but essentially what we're going to do is part of the Krebs cycle remember oxaloacetate and malate maybe okay that doesn't really matter but essentially we're going to take that carbon dioxide and we're actually going to turn it into pyruvate first okay then the pyruvate is going to be broken down in the bundle sheath cell back into carbon dioxide and then ravisco and RDP is going to happen with the Calvin cycle in this cell that's totally separate from this cell why does that matter no oxygen here so I don't have to worry about photo respiration cuz there's no Oxygen that could possibly interfere with robisco because there's no Oxygen anywhere near this cell okay so I can avoid that photo respiration Problem by physically separating the two processes in space okay again the details don't matter I'm telling you what is important okay so C4 plants what they do differently is they have different Anatomy and the anatomy separates rubp and rubisco from the high concentration of oxygen when are hot dry environment is preventing carbon dioxide being brought in okay so unique Anatomy we have a whole new kind of cell in these plants that we don't in any other plant and that helps them avoid photo respiration that's the key okay we're physically separating those processes into different cells so are you repeat and rubisco and carbon dioxide are going to be in the bundle sheet cells only and in the Palisade cells where the light is hitting and we have lots of oxygen and all that kind of stuff there's no rubisco there so we can't have any photo respiration taken place okay examples of these plants sugar cane corn other very successful crops that tend to live in hotter environments right where does sugarcane grow the Caribbean okay so we're avoiding for respiration geographically by having two separate kinds of cell The second one is called cam or Cam plants and this is common inactive to the GE but to do it with time okay so in these plants the light reactions happen during the daytime when does Donata sorry no other way around yeah when the stomata are closed and then the amount of open at night time when it's cooler less water loss mixed with carbon dioxide at night break apart your water during the day okay so we're separating it by time so when can plants at night time when it's cooler it's a lot of open up carbon dioxide comes in oxygen leaves and I don't need to worry about water loss because it's night time it's not that hot so I don't have lots of evaporation and transpiration taking place okay the catch is now I need to store this carbon dioxide temporarily okay so I'm going to turn it into malate so grab it and kick it onto something else and then store it evacules until I'm ready to use it and then in the daytime I close the stomatics cuz it's too hot too dry I will need to maintain water inside the cell so I want to have the least amount of the evaporation and transpiration taking place so I close those pores during the daytime the light reactions happen cuz we have lots of water there cuz we've closed the stomata that gives us the ATP and the nadph that we need and then the malate that we created at night time we can now break apart back into carbon dioxide to make our carbohydrates as well so the reactions are happening in the daytime but all of the gas exchange happens at night because it's not as efficient so if you don't have to worry about water loss C3 is a better way of doing things so I guess that's why I plant like rice are grown and like what about it feels if you put a C3 plant and a C4 plant in a rice field or a wheat field the C3 plant will grow faster and out compete the seat floor pan C4 plant because it's more efficient and sugar game but It's better but C3 is the most efficient way of doing what you need to do as long as you can avoid photo respiration is a problem then you need to use one of the other strategy okay questions Play malic acid PP any of that nonsense all I'm going to ask you is why do we have different types of plants and what's the reason why okay so the reason why we don't use C3 all the time is because total respiration there's a problem what is the respiration you should be able to tell me and these are how these plants solve the problem okay so you need to know a photo respiration is so if you just like and rice fields if they just add plenty of water they just keep their stomach opening Water okay that's when none ideal conditions makes sense the rice will die No is a bit special in that if there's no Oxygen around what does yeast do? anaerobic respiration to make it makes yeah I'll go home tomorrow okay and that's because we're going to be measuring the rate of respiration in these yeast by looking at the volume of carbon dioxide production so we're going to be measuring that rate in very much the same way as the reaction so we're going to be using sugar Plus oxygen to make sure plus water plus h plus email address because you're going to production