PROCESS FIGURE 19.6 Hemoglobin Breakdown

Macrophages break down hemoglobin, and the breakdown products are used or excreted.

cells and conjugated, or joined, to glucuronic acid to form conjugated bilirubin, which is more water-soluble than free bili-rubin. The conjugated bilirubin becomes part of the bile, which isthe fluid secreted from the liver into the small intestine. In theintestine, bacteria convert bilirubin into the pigments that givefeces its characteristic brownish color. Some of these pigments areabsorbed from the intestine, modified in the kidneys, and excretedin the urine, thus contributing to the characteristic yellowish colorof urine. Jaundice (jawn′dis) is a yellowish staining of the skinand the sclerae of the eyes caused by a buildup of bile pigments inthe blood and some tissues. Any process that causes increaseddestruction of red blood cells can cause jaundice, such as damageby toxins, genetic defects in red blood cell plasma membranes,infections, and immune reactions. Other causes of jaundice aredysfunction or destruction of liver tissue and blockage of the ductsystem that drains bile from the liver (see chapter 24).

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ASSESS

13. What is the normal amount of red blood cells in a male? In afemale? 14. How does the shape of red blood cells enable them toexchange gases and move through blood vessels moreeasily? 15. What is the main component of a red blood cell? What isthe primary function of red blood cells? 16. Give the percentage for each of the ways that oxygen andcarbon dioxide are transported in the blood. What is thefunction of carbonic anhydrase? 17. Describe the two basic parts of a hemoglobin molecule.Which part is associated with iron? What gases aretransported by each part? 18. What is the significance of fetal hemoglobin’s differencefrom adult hemoglobin?