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HEME METABOLISM EXAM QUESTIONS AND ANSWERS
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HEME METABOLISM EXAM QUESTIONS ANDANSWERS
an iron-chelating porphyrin prosthetic group common to both myoglobin
and haemoglobin. - ANSWER Heme, specifically Heme B.
Components of Heme B - ANSWER protoporphyrin IX and a ferrous
Fe2+ ion
Heme basics
1. Which cells produce heme?
2. Describe the geometry of the porphyrin ring
3. Stability of heme?
4. Polarity of heme?
5. Function of heme B - specifically the His residues? - ANSWER 1.
Virtually ALL mammalian cells make heme, but its synthesis is most
pronounced in the bone marrow and LIVER because of the requirements
for incorporation into haemoglobin and the CYTOCHROMES,
respectively.
2. A largely PLANAR molecule that consists of one ferrous ion in the
middle of a TETRAPYRROLE ring, called porphyrin.
3. One of the most stable compounds
4. Very nonpolar
5 Basic function is to keep Fe2+ ion protected from oxidation by keeping
it within a certain region
Two main sites of heme production and their targets for delivering heme.
- ANSWER 1. Bone marrow - hemoglobin for blood
2. Liver - heme for microsomal and mitochondrial cytochromes (electron
transfer)
Besides O2 transport and storage, list one other major function of heme
in the body. - ANSWER In mitochondrial cytochromes for electron
transfer.
, Three major types of heme usage (what kind of compounds utilize a
form of heme?) - ANSWER 1. Oxygen binding protein: hemoglobin (O2
transport) and myoglobin (O2 storage)
2. Microsomal and mitochondrial cytochromes (electron transfer)
3. Enzymes (catalysts, use oxygen and/or electrons in the reaction)
a. catalase
b. peroxidases
3. tryptophan pyrrolase
4. prostaglandin synthase
5. Guanylate cyclase
6. NO synthase
*Big idea* Heme is not just for blood O2 transport, it's for many other
things too. Heme is made virtually everywhere in the body. - ANSWER
asdf
Heme biosynthesis
1. Name the initial and final enzymatic steps of heme biosynthesis.
2. For the above steps, what enzymes catalyze them?
3. Where do these steps take place? - ANSWER 1. The initial (ALA-
synthase) and last enzymatic steps (including the insertion of iron ion
into the ring by ferrochelatase) are catalyzed by MITOCHONDRIAL
enzymes, whereas the intermediate oxidative steps take place in the
CYTOSOL.
Heme biosynthesis
1. The ring system of heme is derived from x residues each of x and x.
2. Where is Suc-CoA produced?
3. Where is glycine produced?
4. Where does the iron ion come from? - ANSWER 1. 8 residues each of
Succinyl-CoA from Kreb's cycle and glycine from cytosol.
2
3.
4. The iron ion comes from the cytosol.
x are modified to build Heme A-C and other forms of heme. - ANSWER
Side groups of porphyrin ring
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