Transcription
Hey, let's continue our discussion about anemia. We have talked about iron deficiency anemia, then anemia of chronic disease, and then we'll talk about thalassemia, because those are included in the microcytic anemia. But first, before discussing thalassemia, we need to know about hemoglobin.
So we've said before that hemoglobin consists of heme and globin. The heme consists of iron and protoporphyrin. The hemoglobin is a structure that has four sites for oxygen; in other words, hemoglobin can carry four oxygen molecules. So each hemoglobin molecule can bind four oxygen molecules. Where on the heme portion? Where exactly? In the iron, which is in the heme. And the iron is in which form? The ferrous, not the ferric. As we've said before, Fe2+ binds O2. And please remember that hemoglobin looks like a butterfly—four different subunits. So four subunits; we have four protein subunits and four non-protein groups, or heme groups. So the protein is the globin, and the non-protein is the heme. Hemoglobin: non-protein, protein; the non-protein part, the heme, is synthesized in the mitochondria. But wait, there is no mitochondria in the RBC. Yes, I'm talking about the immature RBC; it has mitochondria. So heme is synthesized in the mitochondria and the cytosol of the immature red blood cell. The globin protein? Since it's a protein, yes, ribosomes. Globin and heme, perfect, that's fine.
So what are the subunits? We have alpha subunit and beta subunit. The normal adult will have two alpha subunits and two beta subunits. That's the general type of hemoglobin. But let's go back to our structure. The heme has iron and protoporphyrin. So here's the heme group: protoporphyrin and iron. The iron is in the ferrous state, Fe2+, binds O2. How about the ferric? No, the ferric is called methemoglobin. So if you have ferric, the hemoglobin is called methemoglobin. Okay, and it's not normal, man. Globin cannot carry oxygen because Fe3+ cannot carry oxygen; only Fe2+ carries O2. So here are two alpha subunits and two beta subunits, and inside them we have the heme group: protoporphyrin and iron in the center. Okay, four of them.
Okay, in adults, hemoglobin has different types. 95% is called adult hemoglobin or hemoglobin A. A for adult consists of alpha2 beta2; means two alpha subunits and two beta subunits. The normal fetal hemoglobin is called hemoglobin F: two alpha subunits and two gamma subunits. But in adults, it only contains or constitutes 1% of the total hemoglobin. Also, we have something called hemoglobin A2: alpha2 delta2, and it forms 1.5 to 3% of the adult hemoglobin. So this is the adult percentage: fetal will have most of them, fetal hemoglobin. But for adults, 95% A, 1% F, 1.5 to 3% A2.
Okay, so that's the foundation until we talk about thalassemia in the next video. Stay tuned! Please subscribe and like us on Facebook. Take care.