Metal Complex in the Blood
Hemoglobin Protein (Interactively view a molecule in this section!) For example , iron complexes are used in the transport of oxygen in the blood and tissues. Though majority of Iron does circulate in the blood as a part of the haemoglobin protein, iron and haemoglobin are two separate entities. Iron is. of hemoglobin was found to bear a significant relationship to the degree of iron saturation of transferrin. This phenomenon was evident through- out the range.
Heme is a porphyrin that is coordinated with Fe II and is shown in Figure 4. Figure 4 On the left is a three-dimensional molecular model of heme coordinated to the histidine residue a monodentate ligand, see Figure 1 of the hemoglobin protein.
On the right is a two-dimensional drawing of heme coordinated to the histidine residue, which is part of the hemoglobin protein. In this figure, the protein is deoxygenated; i. The coordinate-covalent bonds between the central iron atom and the nitrogens from the porphyrin are gold; the coordinate-covalent bond between the central iron atom and the histidine residue is green.Episode 65 - Low Hemoglobin Levels? Don't stuff yourself with Iron Tablets
In the three-dimensional model, the carbon atoms are are gray, the iron atom is dark red, the nitrogen atoms are dark blue, and the oxygen atoms are light red. The rest of the hemoglobin protein is purple. In the body, the iron in the heme is coordinated to the four nitrogen atoms of the porphyrin and also to a nitrogen atom from a histidine residue one of the amino-acid residues in hemoglobin of the hemoglobin protein see Figure 4.
Iron Disorders Institute:: Iron Deficiency Anemia
The sixth position coordination site around the iron of the heme is occupied by O2 when the hemoglobin protein is oxygenated. Questions on the Oxygen-Carrying Protein in the Blood: Hemoglobin One peptide subunit in hemoglobin contains amino-acid residues.
If the subunit were stretched out, it would measure approximately 49 nm in length. However, the longest dimension of the subunit in hemoglobin is only about 5 nm. Briefly, explain how alpha helices may help account for this difference in length. What is the coordination number of Fe in the oxygenated heme group? Briefly, justify your answer by describing the ligands to which Fe is coordinated. Conformational Changes Upon Binding of Oxygen Careful examination of Figure 4 shows that the heme group is nonplanar when it is not bound to oxygen; the iron atom is pulled out of the plane of the porphyrin, toward the histidine residue to which it is attached.
This nonplanar configuration is characteristic of the deoxygenated heme group, and is commonly referred to as a "domed" shape. The valence electrons in the atoms surrounding iron in the heme group and the valence electrons in the histidine residue form "clouds" of electron density.
Electron density refers to the probability of finding an electron in a region of space. Because electrons repel one another, the regions occupied by the valence electrons in the heme group and the histidine residue are pushed apart.
Hence, the porphyrin adopts the domed nonplanar configuration and the Fe is out of the plane of the porphyrin ring Figure 5, left. However, when the Fe in the heme group binds to an oxygen molecule, the porphyrin ring adopts a planar configuration and hence the Fe lies in the plane of the porphyrin ring Figure 5, right. Figure 5 On the left is a schematic diagram showing representations of electron-density clouds of the deoxygenated heme group pink and the attached histidine residue light blue.
These regions of electron density push one another apart, and the iron atom in the center is drawn out of the plane. The nonplanar shape of the heme group is represented by the bent line. On the right is a schematic diagram showing representations of electron-density clouds of the oxygenated heme group pinkthe attached histidine residue light blueand the attached oxygen molecule gray. The oxygenated heme assumes a planar configuration, and the central iron atom occupies a space in the plane of the heme group depicted by a straight red line.
The shape change in the heme group has important implications for the rest of the hemoglobin protein, as well. When the iron atom moves into the porphyrin plane upon oxygenation, the histidine residue to which the iron atom is attached is drawn closer to the heme group.
This movement of the histidine residue then shifts the position of other amino acids that are near the histidine Figure 6. When the amino acids in a protein are shifted in this manner by the oxygenation of one of the heme groups in the proteinthe structure of the interfaces between the four subunits is altered.
Hence, when a single heme group in the hemoglobin protein becomes oxygenated, the whole protein changes its shape. In the new shape, it is easier for the other three heme groups to become oxygenated. Thus, the binding of one molecule of O2 to hemoglobin enhances the ability of hemoglobin to bind more O2 molecules.
This property of hemoglobin is known as "cooperative binding. When hemoglobin is deoxygenated leftthe heme group adopts a domed configuration. When hemoglobin is oxygenated rightthe heme group adopts a planar configuration. As shown in the figure, the conformational change in the heme group causes the protein to change its conformation, as well.
Please click on the pink button below to view a QuickTime movie showing how the amino acid residues near the heme group in hemoglobin shift as the heme group converts between the nonplanar domed and the planar conformation by binding and releasing a molecule of O2.
Explain, in terms of electron repulsion, why the heme group adopts a nonplanar domed configuration upon deoxygenation. Explain how a change in the heme group configuration causes the entire hemoglobin subunit to change shape. Spectroscopy and the Color of Blood The changes that occur in blood upon oxygenation and deoxygenation are visible not only at the microscopic level, as detailed above, but also at the macroscopic level.
Clinicians have long noted that blood in the systemic arteries traveling from the heart to the oxygen-using cells of the body is red-colored, while blood in the systemic veins traveling from the oxygen-using cells back to the heart is blue-colored see Figure 7.
The blood in the systemic arteries is oxygen-rich; this blood has just traveled from the lungs where it picked up oxygen inhaled from the air to the heart, and then is pumped throughout the body to deliver its oxygen to the body's cells.
The blood in the systemic veins, on the other hand, is oxygen-poor; it has unloaded its oxygen to the body's cells exchanging the O2 for CO2, as described belowand must now return to the lungs to replenish the supply of oxygen.
Hemoglobin and Functions of Iron | Patient Education | UCSF Medical Center
Hence, a simple macroscopic observation, i. What causes this color change in the blood? We know that the shape of the heme group and the hemoglobin protein change, depending on whether hemoglobin is oxygenated or deoxygenated.
The two conformations must have different light-absorbing properties. The oxygenated conformation of hemoglobin must absorb light in the blue-green range, and reflect red light, to account for the red appearance of oxygenated blood. The deoxygenated conformation of hemoglobin must absorb light in the orange range, and reflect blue light, to account for the bluish appearance of deoxygenated blood.
We could use a spectrophotometer to examine a dilute solution of blood and determine the wavelength of light absorbed by each conformation. For an approximate prediction of the wavelength of light absorbed and for the colors of light absorbed for a given complementary color, a table such as Table 1 in the introduction to the Experiment "Relations Between Electronic Transition Energy and Color" could be used. Questions on Spectroscopy and the Color of Blood Propose an explanation for why the change in heme group conformation results in a color change.
Difference Between Haemoglobin and Iron
A researcher prepares two solutions of deoxygenated hemoglobin. One solution is ten times as concentrated as the other solution. The researcher then obtains absorption spectra for the two solutions.
Do you expect the wavelength of maximum absorption lmax to be the same or different for the two solutions? If lmax is different for the two solutions, indicate which solution will have a higher lmax. Briefly, explain your reasoning. Do you expect the absorbance A at lmax to be the same or different for the two solutions? If the absorbance is different for the two solutions, indicate which solution will have a higher absorbance.
This phenomenon, known as the Bohr effect, is a highly adaptive feature of the body's blood-gas exchange mechanism.
The blood that is pumped from the heart to the body tissues and organs other than the lungs is rich in oxygen Figure 7. These tissues require oxygen for their metabolic activities e.
Hence, it is necessary for oxygen to remain bound to hemoglobin as the blood travels through the arteries so that it can be carried to the tissuesbut be easily removable when the blood passes through the capillaries feeding the body tissues. In the lungs, the reverse effect occurs: Blood rich in carbon dioxide is pumped from the heart into the lungs through the pulmonary arteries. Arteries are blood vessels carrying blood away from the heart; veins are blood vessels carrying blood to the heart.
In the lungs, CO2 in the blood is exchanged for O2. The oxygen-rich blood is carried back to the heart through the pulmonary veins.
This oxygen-rich blood is then pumped from the heart to the many tissues and organs of the body, through the systemic arteries. In the tissues, the arteries narrow to tiny capillaries. Here, O2 in the blood is exchanged for CO2.
The capillaries widen into the systemic veins, which carry the carbon-dioxide-rich blood back to the heart. The components of this diagram are not drawn to scale.
These species help form interactions between amino-acid residues at the interfaces of the four subunits in hemoglobin. When "salt bridges" form, the subunits are held in a position that "tugs on" the histidine that is attached to the heme iron. This favors the domed configuration, which is the deoxygenated form of hemoglobin. Figure 8 On the left is a schematic diagram of the interface of two subunits of the deoxygenated hemoglobin protein.
These charged groups are held together by ionic interactions, forming "salt bridges" between the two subunits, and stabilizing the deoxygenated form of hemoglobin. When salt bridges form by the interaction of these interfacial histidine residues and nearby negatively-charged amino-acid residues, the deoxygenated hemoglobin structure is favored, and oxygen is released left image in Figure 8.
This negatively-charged group can form salt bridges with the positive charges on the protonated histidines described above. Questions on the Bohr Effect: Does CO2 bind at the same site on the hemoglobin molecule as O2? If not, where does CO2 bind? For blood donors, each donation results in the loss of to mg of iron.
During periods of growth in infancy, childhood and adolescence, iron requirements may outstrip the supply of iron from diet and stores. Iron loss from tissue growth during pregnancy and from bleeding during delivery and post partum averages mg. Breastfeeding increases iron requirements by about 0. Iron Requirements Your "iron level" is checked before each blood donation to determine if it is safe for you to give blood. Iron is not made in the body and must be absorbed from what you eat.
The adult minimum daily requirement of iron is 1. Only about 10 to 30 percent of the iron you consume is absorbed and used by the body. The daily requirement of iron can be achieved by taking iron supplements.
Ferrous sulfate mg, taken orally once a day, and by eating foods high in iron. Foods high in vitamin C also are recommended because vitamin C helps your body absorb iron. Cooking in iron pots can add up to 80 percent more iron to your foods. Consult with your primary care provider before taking iron supplements. Some foods rich in iron include: