
Concept explainers
(a)
Interpretation: To identify the heme degradation product (1) bilirubin, (2) biliverdin, (3) stercobilin, and (4) urobilin in whose production “ring-opening” occurs.
Concept introduction: Hemoglobin is a heme protein present in the red blood cells. The protein part is called globin and the non-protein part is heme. Heme is the prosthetic group that contains 4 pyrrole groups bonded together and has an iron atom in the center. The structure of the heme group is:
The first step of degradation of heme involves opening of pyrrole ring with the release of the iron atom and production of biliverdin. The iron atom released becomes part of ferritin protein. Biliverdin produced is converted bilirubin in the spleen. Bilirubin is then transported to the liver where attachment of sugar residues to the propionate side chains of the bilirubin occurs to make it more soluble. Then more solubilized bilirubin is excreted in bile and finally to the small intestine. In the small intestine, it is converted into stercobilin for excretion in feces or urobilin for excretion in urine.
(b)
Interpretation: To identify the heme degradation product (1) bilirubin, (2) biliverdin, (3) stercobilin, and (4) urobilin in whose production a carbon-carbon double bond is changed to a carbon-carbon single bond.
Concept introduction: Hemoglobin is a heme protein present in the red blood cells. The protein part is called globin and the non-protein part is heme. Heme is the prosthetic group that contains 4 pyrrole groups bonded together and has an iron atom in the center.
The structure of the heme group is:
The first step of degradation of heme involves opening of pyrrole ring with the release of the iron atom and production of biliverdin. The iron atom released becomes part of ferritin protein. Biliverdin produced is converted bilirubin in the spleen. Bilirubin is then transported to the liver where attachment of sugar residues to the propionate side chains of the bilirubin occurs to make it more soluble. Then more solubilized bilirubin is excreted in bile and finally to the small intestine. In the small intestine, it is converted into stercobilin for excretion in feces or urobilin for excretion in urine.
(c)
Interpretation: To identify the heme degradation product (1) bilirubin, (2) biliverdin, (3) stercobilin, and (4) urobilin that is rendered more water soluble by use of a glucose derivative.
Concept introduction: Hemoglobin is a heme protein present in the red blood cells. The protein part is called globin and the non-protein part is heme. Heme is the prosthetic group that contains 4 pyrrole groups bonded together and has an iron atom in the center.
The first step of degradation of heme involves opening of pyrrole ring with the release of the iron atom and production of biliverdin. The iron atom released becomes part of ferritin protein. Biliverdin produced is converted bilirubin in the spleen. Bilirubin is then transported to the liver where attachment of sugar residues to the propionate side chains of the bilirubin occurs to make it more soluble. Then more solubilized bilirubin is excreted in bile and finally to the small intestine. In the small intestine, it is converted into stercobilin for excretion in feces or urobilin for excretion in urine.
The structure of the heme group is:
(d)
Interpretation: To identify the heme degradation product (1) bilirubin, (2) biliverdin, (3) stercobilin, and (4) urobilin which is bile pigment and has a yellowish color.
Concept introduction: Hemoglobin is a heme protein present in the red blood cells. The protein part is called globin and the non-protein part is heme. Heme is the prosthetic group that contains 4 pyrrole groups bonded together and has an iron atom in the center.
The structure of the heme group is:
The first step of degradation of heme involves opening of pyrrole ring with the release of the iron atom and production of biliverdin. The iron atom released becomes part of ferritin protein. Biliverdin produced is converted bilirubin in the spleen. Bilirubin is then transported to the liver where attachment of sugar residues to the propionate side chains of the bilirubin occurs to make it more soluble. Then more solubilized bilirubin is excreted in bile and finally to the small intestine. In the small intestine, it is converted into stercobilin for excretion in feces or urobilin for excretion in urine.
Bile pigments are the colored degradation product of tetrapyrrole carbon arrangement of heme portion of hemoglobin. These are excreted in bile and give characteristic color to urine and feces.

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Chapter 26 Solutions
General, Organic, and Biological Chemistry Seventh Edition
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