[Music] good day Learners Welcome to our new lesson in our previous lesson we talk about photosynthesis specifically the life dependent reaction it happens inside the leaves where plants make their own food through the process of photosynthesis photosynthesis means to put together by light so in the process of photosynthesis they will need raw materials such as carbon dioxide and water now here are the chemical equation for photosynthesis carbon dioxide plus water putting together through light energy inside the chlorophyll to form glucose and oxygen now the overall product of light dependent reaction ATP nadph and oxygen again there are two stages of photosynthesis the light dependent reaction and the light independent reaction we already discussed the light dependent reaction in our previous video and for this video we're going to talk about the light independent reaction or what we called the Calvin cycle Calin cycled is named after Melvin Calvin who won a 1961 Nobel Prize for working out this complex set of chemical reaction Calin cycle occurs in the chloroplast troma just after completing the light reaction of photosynthesis the light reaction helps Calin cycle by providing ATP which is its source of energy and nadph for reducing ability now there are three stages of Calin cycle stage one is the carbon fixation stage two the reduction and stage three is the Regeneration now let's start with stage one which is carbon dioxide fixation carbon dioxide enters through the stomata then diffuse into the stroma of the chloroplast carbon dioxide combined with rudp 5 or ribulose diphosphate to form an unstable six carbon or what we call the rp6 in other books or reference rudp 5 is also called as five carbon molecule ribulose biphosphate carbon dioxide combined with rudp 5 to for form an unstable six carbon dioxide or R udp6 rudp 5 is also known as carbon dioxide acceptor now rp6 splits into two molecules or phosphoglycerate or three phosphoglyceric acid or three PGA now this stage of Calvin cycle is catalyzed by the enzymes rubisco now for stage two the reduction phase using the energy from ATP three PGA molecules are converted into three carbon sugar or glycer alide three phosphate or g3p or phosphoglyceride or pigal this stage involves the enzyme of glycer alide three phosphate dehydrogenase in which nadph from light reaction acts as a donor or acts as electron donor now here are the summary of the change of PGA to pigal PGA plus ATP Plus nadph become pigal plus nadp plus ADP nadp and ADP are available again for conversion during cyclic and noncyclic reaction now for stage three which is the final stage it starts with g3p some g3p or pigal is utilized in making glucose well others are recycled to continue the cycle by combining with a carbon acceptor or rp5 assuming that there are six carbon dioxide enters the reaction 12 pigal will be form 10 of this will be enzymatically rearranged to replace the loss of rudp 5 and only two will become glucose now for us to better understand the Calvin cycle let us use the interactive simulation that I presented to you last video so here we're going to choose Calvin cycle as you can see there are three phases for Calvin cycle for phase one we have the carbon fixation phase two the reduction phase and phase three we have the Regeneration of rubp or rp5 now let's proceed with phase one which is the carbon fixation so this is the Risco or the enzyme used in this phase the rubp or rp5 as you can see there are five carbons rubp or rp5 is also known as carbon dioxide acceptor during this phase carbon dioxide is attached to rubp through the use of the enzymes rubisco then it will become rudp 6 R udp6 will split into two molecules of phosphoglycerate or three phosphoglyceric acid again during carbon fixation carbon dioxide is attached to RPI by the enzymes Risco this forms two molecules of three phosphor lerate for each carbon dioxide added next we have phase two the reduction phase here we're going to use the phosphoglycerate the nadph and ATP from the light dependent reaction using the energy from ATP phosphoglycerate are converted into three carbon sugar while nadph will act as an electron donor so from phosphoglycerate it will become glycer alhy 3 phosphate or G3 3p so we already have one molecule of g3p so let's repeat the process as you can see after the conversion of ATP it will reduce to ADP and nadph will become NP plus and Pi now ADP nadp plus and Pi will be available again for the light reaction again during the reduction phase each molecule of three phosphoglycerate is reduced to form g3p and this requires energy from ATP and electrons from nadph g3p is the final product of the Calvin cycle one molecule of g3p will leave the Calvin cycle and be used to form organic compounds like glucose or sugar now for the last phase which is the Regeneration of rubp or rp5 the other five g3p molecules are used to regenerate rubp so that Calvin cycle can continue the reactions that regenerate rubp require energy to occur this energy comes from ATP so here we're going to drag the three ATP molecules to the reaction site as you can see the rubp or rudp 5 is readily available again to continue the cycle the Calvin cycle can now start over again with the carbon fixation now to summarize photosynthesis let us explain this diagram for light reaction this stage uses water and changes light energy from the Sun into chemical energy stored in ATP and nadph this stage also releases oxygen as a waste product for Calvin cycle this stage combines carbon from carbon dioxide in the air and uses the chemical energy in ATP and nadph to make glucose so that's it see you in our next lesson and if you are new to my Channel please don't forget to hit the Subscribe button and hit the Bell notification so that you will be notified for more videos like this