Hello, in this video we will talk about biogeochemical cycles that relate to life, Earth, and chemical cycles. Then they tell us about how chemicals move from living things to non- living things and back again. And look, up here I've put this mnemonic to remind you of the atoms that life needs to survive. Chumps, carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. But before we talk about cycles, let's see why we need these elements. But try to go ahead of me, that is, think about why we need all this. Let's start with carbon. Why do we need carbon? Well, remember that carbon has four valence electrons. It is very good at forming bonds and can form complex organic materials. So, if we think about proteins or lipids or carbohydrates or nucleic acids like DNA, all of these are built with carbon, and that's because carbon is very good at forming something with itself. Okay? Now let's see why hydrogen is important. Well, hydrogen is important because it can form water, and water is very important for many things, but above all because life can exist with water due to its capacity as a solvent and for providing a medium in which life can exist, but it can also provide energy. For example, this is a reaction of the light phase of photosynthesis. And observe these protons moving through the ATP without rate, generating energy in the form of ATP. So, hydrogen is important not only for water, but also for energy transfer. And now let's look at oxygen. Why is it so important? Well, we need oxygen to form water, but it's also very important in cellular respiration because, look, in the end, oxygen receives the electrons and we can generate a large amount of energy as those electrons leave with the oxygen. And likewise, when we remove them from photosynthesis, a lot of energy can be stored. And well, now you might be thinking, what do we need nitrogen for? Look, we need nitrogen for a couple of things. Here we have an amino acid. And remember that DNA contains the information to create life, but thanks to proteins we are the way we are . So, this is an amino acid and all amino acids have a carbon in the center attached to a hydrogen, but then we have an amino group on one side and a carboxyl group on the other side. And then we have an R group, which is what makes each amino acid different. But look, this nitrogen is very important for forming amino acids or proteins. That's why we need nitrogen to survive. Hm. And on this side we have guanine. And where do we find guanine? Well, if we're talking about DNA, the nitrogenous bases are responsible for storing the information. Guanine is one, but we also have cytosine, thymine, and adenine. So, in guanine here there is a lot of nitrogen, so we need nitrogen from the atmosphere to form the genetic material. And now let's look at phosphorus. What will we need phosphorus for? Well, we need phosphorus for several things. Here we have a phospholipid that forms lipid bilayers and here we have a phosphate group. And if we analyze DNA, remember that in DNA we have sugar phosphate, sugar phosphate, sugar phosphate. So phosphorus is very important in the formation of our genetic material. And something I didn't include, but which is also important, is the ATP. Remember that ATP is adenosine triphosphate. So, with phosphate, when we attach the third phosphate, we can store energy or we can release energy when we let it go. And finally, let's look at the most difficult one. Sulfur. Why do we need sulfur? Well, here I've put two amino acids, cysteine ​​and methine. And we already learned that an amino acid consists of a carboxyl group, an amino group, a carbon and a hydrogen, but we can see that in both amino acids we have sulfur. And sulfur is very important because, well, remember that proteins are what make us who we are and they have a very complex three-dimensional shape . So, if we have a sulfur and a sulfur with two R groups, a bond like the one we have here is formed. This is known as a sulfide bridge or sulfide bond. So, sulfur is important because it gives structure to large proteins. That's why choms is a good way to remember all the elements we need, and we've already seen that we need them for different things. That's why we need to obtain them from our environment. And look, if we think about how energy travels from the Sun to Earth, we know that it travels in the form of light, but once it reaches Earth it also turns into heat. So, in order for energy to reach our planet, it moves in one direction and is converted into heat. But with the nutrients on our planet it's different because nutrients are recycled. For example, the amount of water we have on our planet is static, the amount of carbon is static and they are recycled over and over again in the biosphere, on Earth. In fact, they tried to do that in the Arizona desert. They built this and called it Biosphere Two. They tried to keep all the nutrients needed to survive inside this biosphere that allows light in, but they tried to recycle nutrients and it worked well, but they did n't really achieve a good balance, so from time to time they have to open it. And well, remember that we are talking about biogeochemical cycles. Hm. How will nutrients pass from living things to non-living things? Okay, I'll show you four images of each cycle: the water cycle, the carbon cycle, the nitrogen cycle, and the phosphorus cycle. But I would like you to think about where those nutrients are mostly stored on our planet and how they reach plants and animals and how they return to the environment. Let's start with a cycle we all know, the water cycle. Now, where is the largest amount of water stored on our planet? Of course, it's in the ocean. That's our deposit. And how does it reach the plants? Well, through evaporation, condensation and precipitation, at some point it reaches the plants through their roots that absorb the water. This is how it reaches the plants. And how does it reach the animals? Well, we get water by drinking it or eating plants that contain water, and how do we lose it, that is, how does it return to its source? Well, as you know, plants transpire, they lose water through their leaves, and we lose it through sweat or urination. This way the water returns to the environment to be recycled again. So the water we store in a bottle was once in the ocean, in a plant, in a lake, and so it is recycled over and over again. That's the water cycle. Now let's look at the carbon cycle. Let's see. Most of the carbon that exists on our planet is stored in the atmosphere. But how does it get to the plants? Well, it reaches the plants through photosynthesis, because remember that plants absorb carbon through their stomata and use it to produce sugars. Okay? And how does it return to the environment or how does it reach us? Well, we eat plants or animals that eat plants, and that's how carbon gets into our bodies. But how do we return it to the atmosphere? Well, through breathing. If we breathe, we return carbon to the environment, just like plants do, because remember that they also breathe, and that's how they return it. But one thing that changes the amount of carbon is the burning of fossil fuels. That releases more carbon than is naturally in the atmosphere, but fortunately we have this wonderful carbon recycling. And what do we need carbon for? To build ourselves up. Okay. And now let's look at the nitrogen cycle. Why do we need nitrogen? Okay, remember this for amino acids and nitrogenous bases. Now, in the nitrogen cycle on both sides we need bacteria. So, for nitrogen to reach plants, it all starts with gaseous nitrogen in the atmosphere. Remember that 70% of what we breathe is nitrogen, and for it to reach the plants, bacteria are needed that fix the nitrogen. So before the plant can absorb nitrogen, it has to be fixed, it has to be converted to nitrate, and that's what bacteria do. Some plants even form a symbiotic relationship with bacteria, allowing them to live in their roots, as in this image. But once nitrogen is in plants, how does it get to animals? Well, animals eat plants and we eat the animals that eat plants, but at some point we'll have to return it to the atmosphere. And how does that happen? Well, once again we have bacteria that, through the decomposition of matter, help to return nitrogen to the atmosphere. So bacteria are needed on both sides of the nitrogen cycle to be able to recycle nitrogen. And finally, let's look at the phosphorus cycle. Hm. In this case, phosphorus is not stored in the atmosphere, as is the case with nitrogen and carbon. Rather, phosphorus is stored in rocks. And how will it reach the plants? Well, when it rains, the water wears down the rock and carries it to the ground where it is assimilated. In other words, phosphorus is absorbed through the roots of plants, and that's how they can produce things like their genetic material or ATP. And how do animals get it? Well, when they feed on plants, they carry phosphorus back to themselves. And how will they return it to the ground? Well, when a living thing dies and decomposes, it returns phosphorus, and over time the soil transforms and the phosphorus returns to the rock. This is how phosphorus is recycled over and over again. So these are the biogeochemical cycles through which we can obtain nutrients, take them from the environment, and also return them. I hope it's helpful.