Biology, Eighth Edition (Raven)

Chapter 49: The Circulatory and Respiratory Systems

Hemoglobin Breakdown

Why is the processing of hemoglobin different from the processing of many other macromolecules? Hemoglobin contains a heme group with contains iron. The heme group is used to bind oxygen. Iron is not used in most other types of macromolecules and is not common in biological systems. Conservation of iron is important as any iron lost will need to be replaced from the diet. Therefore the heme group is processed independently from the rest of the hemoglobin molecule in order to ensure conservation of iron to build more hemoglobin.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	In the breakdown of hemoglobin, the globin chains...

		A)	are converted into biliverdin by macrophages.
		B)	are converted into bilirubin by macrophages.
		C)	are broken down by macrophages into amino acids.
		D)	are stored in various tissues.
		E)	contribute to the color of feces.

2.	In the breakdown of hemoglobin, the iron...

		A)	is transported by transferring to the liver.
		B)	is transported by transferring to the spleen.
		C)	is transported by transferring to the red bone marrow.
		D)	all of the above.
		E)	none of the above.

3.	The sequence in the breakdown of the non-iron portion of the heme is...

		A)	heme, bilirubin, biliverdin, conjugated biliverdin, biliverdin derivatives, feces and urine.
		B)	heme, biliverdin, bilirubin, conjugated bilirubin, bilirubin derivatives, feces and urine.
		C)	heme, bilirubin, conjugated biliverdin, biliverdin, biliverdin derivatives, feces and urine.
		D)	heme, biliverdin, conjugated bilirubin, bilirubin, bilirubin derivatives, feces and urine.
		E)	heme, conjugated biliverdin, biliverdin, bilirubin, conjugated bilirubin, feces and urine.

4.	Free bilirubin is transported by the blood to the liver.

		A)	True
		B)	False

5.	Iron is transported in the blood by transferrin.

		A)	True
		B)	False