<s>[INST] context: Cytochromes in complex III receive electrons from the reduced form of CoQ.a. Each cytochrome consists of a heme group (see Figure below) associated with a protein.b. The iron of the heme group is reduced when the cytochrome accepts an electron.Fe3+=Fe2+An iron-deficiency anemia is characterized by small, pale RBCs. The lack of iron reduces the synthesis of heme, so the red cells cannot carry as much oxygen (which gives them the pale color). The cells are small in order to maximize the concentration of hemoglobin present in the cells. A megaloblastic anemia is caused by deficiencies in either vitamin B12 or folic acid (a lack of intrinsic factor will lead to a B12 deficiency named pernicious anemia). These cells are large because the vitamin deficiency interferes with DNA synthesis, and the cells double in size without being able to replicate their DNA. Once the anemia begins, the large blast cells are released by the marrow in an attempt to control the anemia. Hemolytic anemia occurs when the red cell membrane fragments, which can occur with pyruvate kinase deficiencies or a lack of glucose-6-phosphate dehydrogenase activity (which results in reduced NADPH levels). Sickle cell anemia is caused by a point mutation in the b-globin gene, substituting a valine for a glutamic acid.The general structure of the heme group, which is present in hemoglobin, myoglobin, and the cytochromes b, c, and c1. Each cytochrome has a heme with a different modification of the side chains (indicated with the dashed lines), resulting in a slightly different reduction potential and, consequently, a different position in the sequence of electron transfer. [/INST] question: A deficiency of substance iron can result in an anemia. Choose the type of anemia that would occur if the substance were deficient. | options: A: Megaloblastic anemia B: Hypochromic, microcytic anemia C: Hemolytic anemia D: Sickle cell anemia | answer: B </s>