Haemoglobin how does it work

It is composed of four protein chains, two alpha chains and two beta chains, each with a ring-like heme group containing an iron atom. Oxygen binds reversibly to these iron atoms and is transported through blood. Each of the protein chains is similar in structure to myoglobin , the protein used to store oxygen in muscles and other tissues.

However, the four chains of hemoglobin give it some extra advantages, as described below. Aside from oxygen transport, hemoglobin can bind and transport other molecules like nitric oxide and carbon monoxide. Nitric oxide affects the walls of blood vessels, causing them to relax. This in turn reduces the blood pressure. Recent studies have shown that nitric oxide can bind to specific cysteine residues in hemoglobin and also to the irons in the heme groups, as shown in PDB entry 1buw.

Thus, hemoglobin contributes to the regulation of blood pressure by distributing nitric oxide through blood. Carbon monoxide, on the other hand, is a toxic gas. It readily replaces oxygen at the heme groups, as seen in PDB entry 2hco and many others, forming stable complexes that are difficult to remove. This abuse of the heme groups blocks normal oxygen binding and transport, suffocating the surrounding cells. Blood transfusions have saved countless lives. However, the need for matching blood type, the short life of stored blood, and the possibility of contamination are still major concerns.

An understanding of how hemoglobin works, based on decades of biochemical study and many crystallographic structures, has prompted a search for blood substitutes and artificial blood. The most obvious approach is to use a solution of pure hemoglobin to replace lost blood. The main challenge is keeping the four protein chains of hemoglobin together.

In the absence of the protective casing of the red blood cell, the four chains rapidly fall apart. To avoid this problem, novel hemoglobin molecules have been designed where two of the four chains are physically linked together, as shown in PDB entry 1c7d.

In that structure, two additional glycine residues form a link between two of the chains, preventing their separation in solution. Looking through the PDB, you will find many different hemoglobin molecules.

You can find Max Perutz's groundbreaking structure of horse hemoglobin in entry 2dhb , shown in the picture here. There are structures of human hemoglobins, both adult and fetal. RBCs need to be round and flexible to move easily through the bloodstream, and hemoglobin needs to be the right shape, too, for carrying oxygen. The main function of red blood cells is the transport of oxygen from the lungs to the body's cells.

Red blood cells contain a protein called hemoglobin that actually carries that oxygen. In capillaries, oxygen is released to be used by the body's cells. Ninety-seven percent of the oxygen carried by the blood from the lungs is carried through hemoglobin. The other 3 percent is dissolved in the plasma.

Hemoglobin allows blood to move 30 to times more oxygen than could possibly be dissolved in the plasma alone. In the lungs, where the oxygen level is high, hemoglobin combines loosely with oxygen.

The hemoglobin then easily releases that oxygen into the capillaries, where the oxygen level is low. Iron also is needed for proper immune function. About 25 percent of the iron in the body is stored as ferritin, found in cells and circulates in the blood.

The average adult male has about 1, mg of stored iron enough for about three years , whereas women on average have only about mg enough for about six months. When iron intake is chronically low, stores can become depleted, decreasing hemoglobin levels. When iron stores are exhausted, the condition is called iron depletion. Further decreases may be called iron-deficient erythropoiesis and still further decreases produce iron deficiency anemia.

Blood loss is the most common cause of iron deficiency. In men and postmenopausal women, iron deficiency is almost always the result of gastrointestinal blood loss. In menstruating women, genitourinary blood loss often accounts for increased iron requirements. Oral contraceptives tend to decrease menstrual blood loss, whereas intrauterine devices tend to increase menstrual bleeding. Causes of low hemoglobin include:. Several conditions are associated with an elevated hemoglobin level, including:.

In these cases, the increased hemoglobin is the result of the body's compensatory mechanism for low oxygen. A hemoglobin test may show an artificially elevated hemoglobin level due to dehydration. In this situation, hemoglobin is more concentrated when the fluid in the body is low. Hemoglobin may also be elevated in people living at high altitudes due to the oxygen in the atmosphere.

Conditions in which hemoglobin has an abnormal structure include:. People with thalassemia often have life-long anemia and may require frequent blood transfusions. Thalassemia intermedia is also termed "non-transfusion dependent thalassemia" and may not be discovered until adulthood.

A hemoglobin level is usually measured as a part of a complete blood count CBC. The results of other lab tests may also help determine the cause of hemoglobin problems. Normal hemoglobin levels vary by age and sex. If you hear about hemoglobin, you may think of bleeding, especially heavy menstrual bleeding. Yet there is a wide range of disorders that can result in either elevated or decreased hemoglobin.

In addition, abnormal types of hemoglobin can contribute to disease. In order to determine a cause of low or high hemoglobin, your healthcare provider will ask questions, perform a physical exam, and evaluate other blood tests in combination with your hemoglobin level.

Fatigue is the number one sign. This is caused by anemia, a blood disorder resulting from a lack of hemoglobin, the essential protein found in red blood cells. Other symptoms may include headache, dizziness, weakness, pale skin, feeling cold, and trouble breathing.

This has positive effects, enabling the blood to better circulate oxygen during exercise. A blood test called electrophoresis measures the types of hemoglobin in your blood and identifies abnormal hemoglobin including:. Limiting processed foods and red meats can help ward off cancer risk. These recipes focus on antioxidant-rich foods to better protect you and your loved ones. Sign up and get your guide!

University of Rochester Medical Center. Health Encyclopedia.