The Complex Pathway of Oxygen in the Human Body


Everyone is aware of the importance of oxygen. Oxygen sustains life, and we breathe it in and breathe out carbon dioxide in the process of respiration. The unique and complex path that oxygen takes from its entry into the human body through to its use continues to be a fascinating one as are the factors that help or hinder it along its way.

From Air to Circulatory System

The air around us contains about 21 percent oxygen. In the process of breathing, this air enters the lungs. The lungs contain a large surface area of tiny sacs known as alveoli where the oxygen in the air enters into the bloodstream by the process of diffusion. The oxygen-rich blood moves along veins to the heart where it is then pumped to the various parts of the body firstly through the aorta and then through the arteries.

The Importance of Hemoglobin

Oxygen is a gas, and the blood is a liquid, so there must be a specific way that oxygen is carried in the blood to the various parts of the blood. There are two main ways this happens. Some of the oxygen gas dissolves in the plasma and red blood cell water and is carried this way. Most of the oxygen, about 98 percent, is carried in the blood bound to a complex molecule known as hemoglobin. This makes hemoglobin extremely vital for oxygen transport.

Hemoglobin is a protein made up of heme groups and globin chains. Heme groups are specific organic compounds with an iron atom at the center. Each hemoglobin molecule contains four iron atoms in total. The globin chain is a protein chain.

Hemoglobin binds reversibly with oxygen where it is in a higher concentration and releases the vital gas where it is needed and in lower concentrations. Hemoglobin is found in the red blood cells that make up the blood. Red blood cells also carry carbon dioxide from the different parts of the body to the lungs for exhalation. Interestingly, red blood cells are made in the bone marrow, and like all living cells, they initially contain a nucleus. The cell nucleus is the often large structure in a cell that contains the cell’s DNA and other genetic information. When red blood cells mature, they must lose their nuclei in exchange for the hemoglobin that allows them to perform their important function.

Respiration and Metabolism

Oxygen carried in the red blood cells is released all around the body where it is then used in metabolic respiration. Metabolism refers to many different important chemical reactions that take place in the cells to maintain life. These can be to convert food to energy, food to building blocks, or for the elimination of waste and excess compounds.

In cellular respiration, nutrients such as sugar, amino acids, and fatty acids undergo a metabolic reaction with the addition of oxygen to produce energy and waste. For example, glucose can react with oxygen as facilitated by enzymes to form carbon dioxide and water as waste products together with a large amount of heat energy, which is then stored in a compound known as ATP.

Factors that Hinder the Flow of Oxygen

The passage of oxygen from the air to the cells where it is used for respiration has been covered. Various factors may hinder this important sequence and therefore hinder the supply of oxygen to the cells. One example of this is anemia, a condition where the blood does not have enough healthy red blood cells for oxygen transport. This means that the heart must work harder to pump more blood around the body. Liver disease and blood loss also affect oxygen transport in the body.

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