porphyrins
| A | Albumin | |
| B |
CO2 & NH2 |
|
| C |
Bilirubin |
|
| D |
None |
End product of porphyrin metabolism ‑
| A |
Albumin |
|
| B |
CO2 & NH2 |
|
| C |
Bilirubin |
|
| D |
None |
Ans. is ‘c’ i.e., Bilirubin
- Heme is the most important porphyrin.
- It is degraded into bilirubin.
| A |
Uroporphyrinogen synthase |
|
| B |
Uroporphyrinogen decarboxylase |
|
| C |
Protoporphyrinogen oxidase |
|
| D |
Coproporphyrinogen oxidase |
Ans.a. Uroporphyrinogen synthase
(Ref Harper 29/e p3l2-314, 27/e p277)
In porphyrias, uroporphyrinogen synthase enqlme defects lead to Acute Intemittent Porphyria, which shows purely
ne urological manifestation witho ut photosensitivity.
All are true except ‑
| A |
Porphyrinogens are coloured |
|
| B |
Porphyrins emit flurorescence by UV light |
|
| C |
Pyrrole rings of porphyrins are joind by methenyl bridges |
|
| D |
Pyrrole rings of porphyrinogens are joind by methylene bridge |
Ans. is ‘a’ i.e., Porphyrinogens are coloured
- Porphyrins are colored compound and emit fluorescence when illuminated by UV light, i.e. have luminousQ property.
- On the other hand reduced porphyrins (porphyrinogens) are colourless and nonluminous. These reduced porphyrins (porphyrinogens) and not the corresponding porphyrins are the actual intermediates in the biosynthesis of protoporphyrin and heme.
Difference between prophyrinogen and porphyrin
| Porphyringoens | Porphyrins |
| Colourless | Coloured |
| Contain six extra hydrogens and hence also called as reduced Porphyrins | Porphyrinogens autooxidize to their respective porphyrins catalyzed by light |
| Do not absorp at 400 nm | Show characteristic absorbance at 400 nm (regardless of side chain) |
| Do not emit flurorescence, when illuminated by UV light | Porphyrins dissolved in strong mineral acids emit a strong red fluorescence, when illuminated by UV light |
| Pyrrole rings are joined by methylene bridges (— CH,—) | Pyrrole rings are joined by methenyl bridges (— HC=) |
Heme is which porphyrin ‑
| A |
Type I |
|
| B |
Type II |
|
| C |
Type III |
|
| D |
Type IV |
Ans. is ‘c’ i.e., Type III
