by Jason Amores Sumpter
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blood is the fluid that moves through vasculature and is going to perform gas exchange with the tissues. It also plays a role in transporting nutrients, hormones and wastes. Now, blood is going to be made of three main components plasma white blood cells or Lucas sites and red blood cells or Aretha sites. Now, plasma is gonna make up the majority of blood. Let me just jump out of the way here so I can fill this in. So we have plasma. That's our main component. And it's like the liquidy portion of blood, which is why, in a test tube it's going thio be on the surface, right? It's gonna be less dense than the stuff below, so it's mostly made of water. It also has dissolved electrolytes, organic compounds and dissolved gas is now the smallest portion of blood is going to be made up of white blood cells. And they're also gonna be some of what are called him platelets. In here. Now, white blood cells are cells of the immune system that are gonna help fight and identify infections. We'll talk more about them in lesson on, uh, the immune system. Platelets are small cell fragments, and they're gonna play an important role in blood clotting, which is a wound response. So if there's damage to the vasculature, they will rapidly plug those holes. And they'll also you know, um, there will also be other factors and molecules that air recruited to help seal up that wound site. But the platelets offer this rapid response to very quickly clot and plug any holes now. Sometimes clots form when they shouldn't, and we call these type of clots thrombosis or a singular would be thrombosis. This is a clot that is going to form in a blood vessel and block flow. Not very good that can lead to some seriously bad news stuff. Now, red blood cells kind of get all the credit in terms of blood. That's what gives blood its color. And that's also going to be what carries theme oxygen. It's going to carry oxygen using this protein called hemoglobin, and it should be noted that red blood cells actually lack nuclei and organelles at maturity, and this is in part so that they can get packed as full as possible. With hemoglobin, you can see a picture of a red blood cell here thes air red blood cells. And they sort of have ah kind of dona t disk shape, this dark spot in the center that is like a depression in the red blood cell. You'll find it on both sides. They kind of have, like, a weird ring shape to them, and they're actually going to be produced in bone marrow. So are white blood cells, but their whole process of development is a bit more complicated. So red blood cells are gonna be produced in bone marrow. And actually, there's a hormone secreted by the kidney that will stimulate red red blood cell production. We call that erythropoetin. So red blood cells are Aretha sites, or with pro erythropoetin is a hormone that stimulates red blood cell production. And here you can see some white blood cells or Lucas sites. There's quite a variety of cells that fall under that category, and we'll talk more about those in lesson on the immune system. Now, red blood cells get their distinctive color due to what's known as a respiratory pigment. This is gonna be a molecule that increases the oxygen carrying capacity of blood, and the reason it gets its name the reason blood has that distinctive colors because it's actually going to change color from oxygen binding, which is kind of cool, because by looking at blood, you can tell based on the color color, whether it's oxygenated or de oxygenated. Now there are other respiratory pigments aside from hemoglobin, Um, but we're not really going to focus on those. We're gonna focus on hemoglobin, which is what's in our red blood cells. This is a protein that's actually made of four poly peptide sub units, which means that it has Quaternary structure and you can see those sub units right here there, each in different colors, so each one of those is a sub unit of hemoglobin. This whole thing is hemoglobin, and each one of those subunits contains what's called a heem. This is what's going to actually bind the oxygen. It's a co factor in the protein, and it contains what's called a poor foreign ring, and it's going to have iron in its boyfriend ring, and that iron is going to be reduced and oxidized in order to transport. Oh, too. So basically, Thio bind oxygen. That iron is going to be oxidized. And when a red blood cell wants to offload its oxygen. The iron is going to be reduced, meaning that oxygen will come off and move into the tissue. Now what's cool about this port friend ring and I think is worth mentioning. Just because it's a nice theme of biology is how nature tends to conserve structures. So this is a structure here being used for oxygen transport. We've seen something similar before in terms of photosynthesis. This here is also poor friend ring. It has magnesium at its center, so not iron, but same structure. You know what this is? This is chlorophyll. This is what plants use to absorb sunlight. Energy. So pretty cool stuff that that structure will appear in such radically different places for such radically different purposes. Just kind of an interesting little side note. No humans actually also have this other respiratory pigment and other animals or other mammals due to it's called myoglobin. And this is the primary pigment of skeletal muscles. And actually it's on Lee going to contain one heem instead of the four he seems that we see in hemoglobin and it binds oxygen tighter. Then hemoglobin does, and this is going to be super important. When we talk about oxygen dissociation, curves and oxygen binding, my global plays a very important role. For muscles, however, it's it's a kind of sophisticated, and we'll get to it later when we talk about thief physiology of hemoglobin, an oxygen binding now, last thing I want to mention is a disease that results from abnormal chema globe hemoglobin. It's called sickle cell disease, and basically what happens is the hemoglobin proteins have a mutation, and it causes them to aggregate in red blood cells. And so this is going to result in a distorted shape, and it's going to inhibit their functions. So this is a nice, normal, healthy red blood cell, and this is a sickle cell. You can see very clearly that you know this. The shape of the cell is all wrong, and sickle cell disease can be life threatening. However. Interestingly, it's stuck around in the population because it's controlled in a single gene locus and essentially, um, people who are hetero zegas for this gene, meaning you know, they have the dominant and recessive Leal's actually do better against against malaria than people who have the dominant forms of the illegals that would, you know, lead to these nice, healthy red blood cells. So the reason that recessive mutant alil, which when you have two of them, you know you'll get thes sickle cells. The reason that stuck around the population is again because of malaria. It actually helps confer resistance to malaria. So even though sickle cell disease can kill you, hetero zygotes are at an advantage when it comes to you dealing with malaria. With that, let's flip the page.