in the previous video we were actually talking about the structure of the tilid and I told you that in the Tyler covid itself they have these things called ATP synthes um electron transport chains photosystem 1 and photosystem 2 together with that enzyme um and most students have difficulties understanding these things called photo systems so this video is to just explain what these photos systems are all about so if I were to just take out one of the photos systems and TRW it out on the right side I don't care whether it's photosystem one or photosystem 2 they have a lot of similarities if you notice in the photos systems I'm drawing out these circles and these circles they have different sort of colors correct and at the bottom there there are two green circles two large green circles joined together each of those circles are referred to as something called photosynthetic pigments and in the first video about photosynthesis I told you that the function of this pigments were to actually absorb light so that the light energy can be harnessed to synthesize ATP but as you can see over here though there are many different colored pigments you can see like for example like a I guess that's maroon maroon orange purple and green pigments you don't have to memorize the Colors by the way don't worry about that but the point I'm trying to make here is there are many different types of pigments in the photo system the pigments at the top the first six pigments at the top there uh maroon orange and purple uh you don't have to know the number as well uh they are referred to as accessory pigments and the two pigments at the bottom which are the two green ones joined together are called the reaction Center the reaction Center is important too because you must know that the reaction Center is made up of two chlorophyll a pigments this is important that's why I put a that's why I put a star over there you need to know that each photo system whether it's photosystem one or photo system too it doesn't matter the photos systems are made out of many accessory pigments and it also has two chlorophyll a molecules joined together to form something known as the reaction Center why does the photosystem have different types of pigments the reason here is as follows each pigment can absorb absorb a specific wave length of light as an example you can see that there is a pigment which is the orange color pigment over there and also the purple pigment now the orange pigment they can only absorb light at a 400 nanom wavelength again don't memorize this and the purple pigment for example might only be able to absorb light with 700 nanom wavelength let's see this in action for example if I shine purple color light over here which is 400 nanom I'm shining it to the purple pigment look at what happens to the light the purple light gets reflected and this is not good because if the plant wants to carry out photosynthesis it needs to absorb as much light as possible so if it cannot absorb 400 nanom you know that's light that is not being absorbed and that is light that is wasted so that is why the orange pigments are present because when 400 nanom wavelength or purple light hits the orange pigment what happens it doesn't get reflected the orange pigment can then absorb the light in another case the purple pigment is not useless because the purple pigment can help to absorb different wavelengths of light if the question asks you why do photosystems have many different types of pigments the reason is because they allow the absorption of different wavelengths of light to maximize the absorption of Light which uh is in a range of 400 nanom to 700 nanom now once they absorb the light what do they do to the energy that they have absorbed the energy is then transferred to the reaction Center which is made up of two chlorophyll a molecules and when the reaction Center receives enough energy we will say that the reaction Center becomes photoactivated which means to say the reaction Center has been activated due to the presence of light and when there's enough energy in the reaction Center they will release out a high energy electron so you might be thinking okay why why does it have to release out an electron again we will talk about that as we go along we are going to explain this bit by bit I just need you to understand what the photo systems supposed to do so in a nutshell what the photosystems do is they will first absorb different wavelengths of light they will transfer the energy to the reaction Center which will cause something called the photo activation of the reaction Center and an electron is released from the reaction Center so again why does it have to release the electron we will talk about that when we are looking at the light dependent reaction in detail so again just just be aware of this now when you're comparing photosystem 2 remember there are two types of photosystem by the way photosystem 2 and photosystem 1 the good news is both of them have the same almost the same type of pigments they function the same way where they absorb the light transfer the energy to the reaction Center and the reaction Center releases out an electron the only thing I need you to be aware of is that photosystem 2 it has an enzyme over there uh which I've represented in the blue pacman and the enzyme in the photosystem too is called called an oxygen evolving complex what is the function of the oxygen evolving complex again I am going to talk about this later I know I know I know if you're listening to me in my videos you're going to be like H he's always saying later later later later later I swear I'm doing this for a reason because if I were to explain everything immediately it's not going to make any sense at all so do not worry about this so what I just need you to know is photosystem 2 has an enzyme embedded within it called the oxygen evolving complex enzyme that's it now this part over here is a very interesting part I don't need you to memorize this part this is not needed for the exam but I need you to be aware of it because it makes photosynthesis so much easier to explain you see when the light energy is absorbed by the pigments and they transfer the energy to the reaction Center the reaction Center has to release an electron correct we know that that that's how the photosystem works but when the reaction Center releases out an electron that electron that is lost must be replaced by another electron okay you don't need to memorize that I just need you to understand this the reason is because again the reason is not important but if the reaction Center continues losing electrons it will destabilize its structure and it might bring break down so to prevent the reaction center from from being broken down or oxidized Beyond repair whatever electron that is lost must be replaced which means to say if it loses two electrons two new electrons need to come in and replace it so that it stabilizes its structure you don't need to memorize this but I just need you to be aware of this particular feature