Chapter 18 - Section 18.2 - Study Guide - Assess Your Learning Outcomes - Page 705: 9

When hemoglobin is broken down during the disposal of expired red blood cells (RBCs), its components are processed and eventually excreted from the body. The breakdown of hemoglobin leads to the formation of various pigments that are related to the colors of bile, feces, and urine. Here's how the body disposes of hemoglobin and how it relates to the pigments of bile, feces, and urine: 1. **Hemoglobin Breakdown:** When old RBCs are removed from circulation by macrophages, the hemoglobin within them is broken down. Hemoglobin consists of two main parts: the heme group, which contains iron, and the globin protein. 2. **Formation of Biliverdin and Bilirubin:** The iron-containing heme group is initially converted into biliverdin through the action of an enzyme called heme oxygenase. Biliverdin is green in color. 3. **Conversion of Biliverdin to Bilirubin:** Biliverdin is then rapidly converted into bilirubin through the action of an enzyme called biliverdin reductase. Bilirubin is yellow-orange in color. 4. **Processing in the Liver:** Bilirubin, which is not very water-soluble, is transported to the liver, where it undergoes further processing. In the liver, bilirubin is conjugated (chemically modified) to make it water-soluble. Conjugated bilirubin is then excreted into the bile. 5. **Bile Production and Storage:** Bile is a digestive fluid produced by the liver and stored in the gallbladder. It contains conjugated bilirubin, among other components. When needed for digestion, bile is released into the small intestine. 6. **Excretion:** In the small intestine, conjugated bilirubin plays a role in the digestion and absorption of fats. Some of it is further modified by bacteria in the large intestine, resulting in the formation of urobilinogen. 7. **Urobilinogen:** Urobilinogen can be reabsorbed into the bloodstream and then excreted by the kidneys into the urine. Small amounts of urobilinogen contribute to the yellow color of urine. 8. **Stool Color:** The remaining urobilinogen that is not reabsorbed by the body is converted into urobilin and stercobilin by bacteria in the large intestine. These compounds give feces their characteristic brown color. In summary, the disposal of hemoglobin from expired red blood cells results in the formation of biliverdin, bilirubin, and other related pigments. These pigments contribute to the colors of bile, feces, and urine. Bilirubin, in its various forms, plays a central role in this process, being excreted in bile to give bile its color, contributing to the color of feces, and influencing the color of urine. The breakdown and excretion of these pigments help the body eliminate waste products and maintain overall health.

When hemoglobin is broken down during the disposal of expired red blood cells (RBCs), its components are processed and eventually excreted from the body. The breakdown of hemoglobin leads to the formation of various pigments that are related to the colors of bile, feces, and urine. Here's how the body disposes of hemoglobin and how it relates to the pigments of bile, feces, and urine: 1. **Hemoglobin Breakdown:** When old RBCs are removed from circulation by macrophages, the hemoglobin within them is broken down. Hemoglobin consists of two main parts: the heme group, which contains iron, and the globin protein. 2. **Formation of Biliverdin and Bilirubin:** The iron-containing heme group is initially converted into biliverdin through the action of an enzyme called heme oxygenase. Biliverdin is green in color. 3. **Conversion of Biliverdin to Bilirubin:** Biliverdin is then rapidly converted into bilirubin through the action of an enzyme called biliverdin reductase. Bilirubin is yellow-orange in color. 4. **Processing in the Liver:** Bilirubin, which is not very water-soluble, is transported to the liver, where it undergoes further processing. In the liver, bilirubin is conjugated (chemically modified) to make it water-soluble. Conjugated bilirubin is then excreted into the bile. 5. **Bile Production and Storage:** Bile is a digestive fluid produced by the liver and stored in the gallbladder. It contains conjugated bilirubin, among other components. When needed for digestion, bile is released into the small intestine. 6. **Excretion:** In the small intestine, conjugated bilirubin plays a role in the digestion and absorption of fats. Some of it is further modified by bacteria in the large intestine, resulting in the formation of urobilinogen. 7. **Urobilinogen:** Urobilinogen can be reabsorbed into the bloodstream and then excreted by the kidneys into the urine. Small amounts of urobilinogen contribute to the yellow color of urine. 8. **Stool Color:** The remaining urobilinogen that is not reabsorbed by the body is converted into urobilin and stercobilin by bacteria in the large intestine. These compounds give feces their characteristic brown color. In summary, the disposal of hemoglobin from expired red blood cells results in the formation of biliverdin, bilirubin, and other related pigments. These pigments contribute to the colors of bile, feces, and urine. Bilirubin, in its various forms, plays a central role in this process, being excreted in bile to give bile its color, contributing to the color of feces, and influencing the color of urine. The breakdown and excretion of these pigments help the body eliminate waste products and maintain overall health.