in this video we're going to take a look at photosynthesis and cellular respiration so by the end of this video you are going to be able to compare and contrast the processes of photosynthesis and cellular respiration as well as explain their complementary rules in ecosystems so to get started we first need a little bit of background knowledge about chemical reactions so a chemical reaction is a process that transforms one or more substances into one or more new and different substances and so what happens in a chemical reaction is that atoms are rearranged in a chemical reaction the starting materials are called reactants and the substances that are created are called products and generally we write that reactants with an arrow form products so now that we know that let's take a look at photosynthesis and cellular respiration so in nature these are two very important reactions that occur in living organisms and they are essential to most life on Earth starting with photosynthesis if we break the word down photo means light and synthesis means to put together or compose and so photosynthesis is a process used to convert the sun's energy or sunlight into chemical energy now in Plants the substances in leaves that absorb the light is called chlorophyll and the chemical energy is stored in glucose or sugar and so the reaction here that occurs is that water or six Waters react with six carbon dioxides and they take the light energy and then convert that into glucose which is C6H12O6 as well as oxygen cellular respiration is a process that releases usable energy in the form of what we call ATP from the chemical energy that's stored in glucose molecules so all animals all living things all cells need a continuous supply of energy in order to function because they need it to grow to repair and to reproduce cellular respiration happens in both plants and animals and since animals do not do photosynthesis they have to eat glucose and get their glucose by eating food which they're eating plants or eating other animals that have already consumed the plants if we take a look at the reaction here glucose then C6H12O6 reacts with oxygen and is broken down into water H2O carbon dioxide CO2 and it also then releases energy photosynthesis and cellular respiration are reactions that complement each other in the environment they are in reality the same reactions but occurring in Reverse of each other so as you can see photosynthesis requires the products of respiration while respiration requires the products of photosynthesis so they work together so that what is made from one process is used in the other which allows the carbon dioxide and the oxygen or the carbon in the oxygen that organs organisms consume and produce to be cycled through the ecosystem this helps to regulate atmospheric concentrations of carbon dioxide and oxygen another thing these reactions have in common is that they both deal with the conversion of energy in photosynthesis light energy is captured from the Sun and stored in glucose in cellular respiration however the energy in glucose is converted into chemical energy by living organisms so this energy allows their bodies to perform life-sustaining activities now that we've explored some of the similarities between photosynthesis and cellular respiration let's compare and contrast the two processes together so in photosynthesis food is made whereas in respiration food is broken down in photosynthesis energy from the sunlight is stored in glucose whereas in respiration the stored energy in glucose is released in photosynthesis carbon dioxide is taken in whereas in respiration CO2 is released in photosynthesis oxygen is given off whereas oxygen is taken in in respiration in photosynthesis this occurs in Plants algae as well as certain types of bacteria whereas respiration happens in all living organisms light is needed for photosynthesis where whereas no light is needed for respiration and finally photosynthesis occurs in organelles called chloroplasts whereas respiration happens in the mitochondria and the cytoplasm now photosynthesis and cellular respiration are interconnected and essential to life on Earth these systems allow the carbon and the oxygen that organisms consume and produce to be cycled through the ecosystem they work together so that what is made from one process is used in the other without them the ecosystem would run out of carbon dioxide and oxygen which means all the plants would die and oxygen requiring life would not survive finally let's just take a quick look at the impact on ecosystems so photosynthesis and cellular respiration are essential in maintaining the interconnected relationship between plants humans and animals and directly or indirectly affect all life on Earth photosynthesis serves as the primary energy process for most trees and plants their energy continues on to fuel nearly all other organisms in the ecosystem from bacteria to animals the vast majority of Earth's ecosystems are ultimately supported by sunlight so some organisms use the energy produced by plants directly some eat organisms that ate plants some eat organisms that ate organisms that a plants and so on ultimately food webs lead back to the energy produced by plants through photosynthesis organisms consume this energy which is stored within sugars and unlock through cellular respiration to power their activities so as a result photosynthesis and cellular respiration are incredibly important in ecosystem ecology that sums up then the processes of photosynthesis and cellular respiration and their importance to ecosystems so let's move on to our next task