Hemoglobin - It Takes My Breath Away

I got a call the other day from the Blood Bank. They wanted me to come in and donate. I have O+ blood, the most common, and they are in need. I donate three or four times a year and I was due so I went in. It got me thinking about how important blood is to life and how it plays a significant role in our salvation (Romans 5:8-10 NIV). But I was also thinking; "What is the most critical component of blood?"

Blood has four key components, red blood cells (RBC), white blood cells (WBC), platelets and plasma. Plasma is mostly water and is what carries the rest of the components throughout the body. Platelets are important for blood clotting. White blood cells are the soldiers of our immune system. Red blood cells are the most critical part. They carry oxygen from the lungs to the rest of the body, all the way to the cellular level. And what is it that does this work? Hemoglobin.

	Hemoglobin is the carrier of oxygen from the lungs to the cells and it returns CO2 to be exhaled as waste. Hemoglobin is the major protein inside the RBCs, accounting for 97% of the non-water weight of red blood cells. In humans it is made up of four protein sub-units, two each alpha (141 amino acids) and beta (146 amino acids) protein subunits, joined together to form the full hemoglobin molecule. Each protein subunit also contains a heme group, a small iron containing molecular structure that bonds with the O2 molecule. With hemoglobin, the blood can carry seventy times the oxygen that it would carry if the oxygen was dissolved in plasma alone.
Hemoglobin: Wikipedia red = alpha protein blue = beta protein green = heme group

The iron in the heme group bonds to the oxygen to transport it. This "oxyhemoglobin" is red in color. The oxygen bonds to the hemoglobin in the lungs and is released at the cellular level where it is used in energy production. The hemoglobin then returns to the lungs as "deoxyhemoglobin" which is purplish-blue in color. Each hemoglobin molecule can bind up to four oxygen molecules. The binding is "cooperative" in that as each oxygen molecule is bound, it bends the hemoglobin protein in such a way as to improve the binding of oxygen at the remaining heme groups.

People with iron poor blood, or iron deficiency, have fewer RBCs and thus cannot transport oxygen efficiently. Anemia develops slowly in those with low iron intake and can result in weakness, dizziness and shortness of breath. Occasionally one of the hemoglobin protein sub-units is affected by a rare genetic mutation. Most of the time the mutation causes no physiological affect but sometimes the alteration in the protein changes certain aspects of its behavior. Two types of disorders that can result from genetic mutations include sickle cell disease and thalassemia.

In sickle cell disease, the alpha chain is normal. The disease-producing mutation exists only in the beta chain. People who have one sickle mutant gene and one normal beta gene are carriers of the sickle cell trait but do not develop sickle cell anemia. It requires both genes to be mutant genes for sickle cell anemia to be expressed. This results in defective hemoglobin molecules that stick together and cannot efficiently carry oxygen.

In thalassemia, the body produces insufficient quantities of one of the two protein subunits. The subunits created are properly formed, just in low concentrations. This creates an imbalance between the number of alpha proteins and beta proteins. This imbalance damages the red blood cells, producing anemia. A number of other genetically altered forms of hemoglobin also exist that can cause disease.

Besides oxygen, hemoglobin can also bond with carbon monoxide (CO). Hemoglobin actually bonds carbon monoxide much more readily than oxygen. This is why carbon monoxide is so deadly. Smoking, car exhaust and improper furnace ventilation are major sources of carbon monoxide. A home CO detector is available to warn if levels get dangerously high. Carboxyhemoglobin (hemoglobin with bound CO) is a very bright red color and makes the skin appear pink in CO poisoning. Other compounds that also inhibit oxygen binding include cyanide (CN), nitric oxide (NO) and hydrogen sulfide (H₂S), all of which are toxic.

Glycosylated hemoglobin is a form of hemoglobin to which glucose is bound. This binding of glucose to hemoglobin serves as a record for the average blood glucose levels over the lifetime of the red blood cells, typically 120 days. The levels of glycosylated hemoglobin can be measured to monitor the long-term control of diabetes mellitus. This measurement is called hemoglobin A1c. Diabetics who keep their A1c levels close to 7 have a much better chance of avoiding diabetic complications than those whose levels are 9 or higher.

Hemoglobin is essential in the transport of oxygen within the vertebrates and oxygen is essential for almost all animal life. God has created a balance between the animal kingdom (generally uses O₂ and generates CO₂ as waste) and the plant kingdom (generally uses CO₂ and generates O₂ as waste). This balance helps to maintain our environment for the continued support of life as we know it. In the same way the blood of Christ does this for our souls, it creates and maintains an environment for the support of our spiritual life in Him.

"Whoever eats My flesh and drinks My blood has eternal life, and I will raise him up at the last day. John 6:54 (NIV)"