USMLE Step 1 Respiratory Physiology Review 60 14 Oxygen Transport

USMLE Step 1 Respiratory Physiology Review 60 14 Oxygen Transport

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Play USMLE Audio MP3 60 14  Oxygen Transport Below

Begin 60 14  Oxygen Transport Transcription

Moving now to oxygen transport. Once it has crossed the respiratory membrane, the oxygen dissolves in the plasma of the pulmonary capillaries. However, the solubility of oxygen in the liquid is very low, so only a small percent of the oxygen in the blood remains in the plasma as physically dissolved gas.
What percent of the oxygen in blood is physically dissolved gas?

  •    Less than 2 percent.

From the plasma most of the oxygen diffuses into the red blood cells. What is the
component of red blood cells with which the oxygen forms a reversible chemical bond. It starts with an H.

  • The hemoglobin in red blood cells form a chemical bond with the oxygen.

A hemoglobin molecule is made up of two parts.  What is the protein part of hemoglobin called?

  • Globin is the protein part of hemoglobin.

In addition to the globin, each hemoglobin molecule has four disk shaped pigment molecules that contain iron. What are these called? The answer starts with an H.

  •   Hemes.

Each molecule of hemoglobin is able to combine with how many molecules of oxygen?

  •  4

How does hemoglobin affect the concentration of oxygen in the blood?

  • Hemoglobin greatly increases the concentration of oxygen in the blood.

Student doctor please pause the tape and summarize what has been discussed about the solubility of oxygen and the composition of hemoglobin.

  • Once it has crossed the respiratory membrane, the oxygen dissolves in the plasma of the pulmonary capillaries. Because the solubility of oxygen in a liquid is so low, less than 2% of the oxygen in blood remains in the plasma as physically dissolved gas. From the plasma most of the oxygen diffuses into the red blood cells where it forms a reversible chemical bond with hemoglobin. The protein part of hemoglobin is called globin. In addition to the globin, each hemoglobin molecule has four disk shaped pigment molecules that contain iron. These are the hemes. Each molecule of hemoglobin is able to combine with four molecules of oxygen. Hemoglobin greatly increases the concentration of oxygen in blood.

 

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