in living systems structure is always related to function. There's no room to waste energy on things for frivolous reasons, and you can see this relationship between structure and function all the way down. At the molecular level, consider a membrane protein that needs to span the hydrophobic plasma membrane, yet interact with the Hydra Filic environments inside and outside the cell. Also. Ah, lot of these membrane proteins, for example, transport ions, which are charged molecules, right, are charged particles. I mean now with the membrane protein, it's going toe have hydrophobic regions, right. Those hydrophobic regions, they're gonna interact with the membrane and in part anchor it into the membrane. And it's going to have Hydra Felix regions which will interact with the intracellular and extra cellular environment. And assuming, for example, it's transporting an eye on it will have a hydra filic internal environment to get that charge particle through. We also see this relationship between structure and function. At the cellular level. Consider cells that perform secretion right. They need thio export lots of molecules. What is the organ l involved with exporting stuff? Golgi. Apparatus. Well, here you can see a nice electron microscope view of a cell that is chock full of Golgi apparatus. All this fold e stuff here is Golgi apparatus. And that's because this is a secretary cell, a cell that plays a role in secrete ing substances in the body. So it's gonna be chock full of Golgi apparatus to carry out that function efficiently. And of course, we see this on the organ, the whole organism level as well. Uh, the famous example, of course, being the flower that Darwin saw, which you can see right here. And this flower has a really long tube. It's kind of hard to see in this image, but just take my word for it. This tube that leads to the nectarine, the nectar producing portion of the flower, can be almost a foot long. And when Darwin first saw it, he said, You know what? I bet there's an animal out there that has a proboscis cas that can reach all the way down there and get that nectar. And there it is, this moth right here with this huge proboscis Cus, you can see it uses to feed feed on nectar from this flower, so structure is going to fit function Now, when we talk about on organisms, anatomy and physiology, we're gonna be talking a lot about tissues and organs. A tissue is going to be a group of cells that carries out a specific function, and here you can see a sample of some tissue from a lung. Thes cells that are stained in this color are, um, are part of a tissue. They're going to carry out a specific function, and they're gonna work in concert with other tissues in lung to, you know, carry out the function of the lungs to you perform gas exchange. Ah, the lungs themselves are in Oregon, which is basically composed of multiple tissues and will carry out some specialized functions. So, for example, in the lungs you need tissues where gas exchange can occur. There's also tissues that produced, uh, mucus substance to help prevent the lungs from collapsing. There's a lot of stuff that goes on to just carrying out that one specialized function of the organ. It takes multiple tissues working together, and then those organs will actually work in concert with each other in what we call organ systems. This is a group of organs that works together to carry out some function, right? So while the lungs might perform gas exchange, they need other structures to carry out the function of breathing. So let me jump out of the way here and here. You can see the respiratory system. This is the organ system responsible for breath. And you can see it has multiple components of which the lungs, these guys, which you can see in pink over here, the lungs are only one Oregon in this system, right? It requires many other things working in concert to accomplish the job. So with that, let's turn the page and talk about tissues.