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The question reads:
"In the absence of uroporphyrinogen synthase, uroporphyrinogen I (uroI) is synthesized in place of the biologically active uroporphyrinogen III (uro III)."
Conversion of uro I into uro III requires:
A. An isomerase, converting a symmetric molecule into an asymmetric molecule.
B. An isomerase, converting an asymmetric molecule into an asymmetric molecule.
C. A kinase, converting a symmetric molecule into an asymmetric molecule.
D. A kinase, converting an asymmetric molecule into a symmetric molecule.
A is correct. We have to look at the two structures given in the question. First, there is no difference in the chemical constituents of the two molecules. However, the atoms are arranged differently. For this reason, an isomerase is the enzyme that would be involved. Next, in looking at the picture one should arrive at the conclusion that uro I is a symmetric molecule, symmetric around the center point of the molecule (where the iron would be bound). By switching one set of constituents, uro III is produced. Switching these constituents produces an asymmetric molecule. The correct choice is A.
Can someone please help me understand why one structure (uro I) is symmetric and one structure (uro III) is asymmetric? I am having a hard time picturing it.
"In the absence of uroporphyrinogen synthase, uroporphyrinogen I (uroI) is synthesized in place of the biologically active uroporphyrinogen III (uro III)."
Conversion of uro I into uro III requires:
A. An isomerase, converting a symmetric molecule into an asymmetric molecule.
B. An isomerase, converting an asymmetric molecule into an asymmetric molecule.
C. A kinase, converting a symmetric molecule into an asymmetric molecule.
D. A kinase, converting an asymmetric molecule into a symmetric molecule.
A is correct. We have to look at the two structures given in the question. First, there is no difference in the chemical constituents of the two molecules. However, the atoms are arranged differently. For this reason, an isomerase is the enzyme that would be involved. Next, in looking at the picture one should arrive at the conclusion that uro I is a symmetric molecule, symmetric around the center point of the molecule (where the iron would be bound). By switching one set of constituents, uro III is produced. Switching these constituents produces an asymmetric molecule. The correct choice is A.
Can someone please help me understand why one structure (uro I) is symmetric and one structure (uro III) is asymmetric? I am having a hard time picturing it.