Heme Synthesis

Question 1

Name the heme proteins

Answer 1

hemoglobin, myoglobin, cytochrome, catalase, tryptophan pyrrolase

Question 2

What are porphyrins

Answer 2

Intermediates during heme synthesis

Question 3

What joins pyrrole rings together

Answer 3

methenyl

Question 4

Which atom in the pyrrole ring attaches to metal ion

Answer 4

Nitrogen

Question 5

Porphyrin Intermediates during heme synthesis

Answer 5

Uroporphyrin, Coporphyrin and Protoporphyrin

Question 6

Side chains of uroporphyrin

Answer 6

4 acetyl and 4 proprionyl

Question 7

Side chains of coporphyrin

Answer 7

4 methyl and 4 proprionyl

Question 8

Side chains of protoporphyrin

Answer 8

4 methyl, 2 vinyl and 2 propionyl

Question 9

Uroporphyrin is excreted in urine or feces?

Answer 9

Urine

Question 10

Coporphyrin and Protoporphyrin is excreted in urine/feces?

Answer 10

Feces

Question 11

Which type (I or III) of uroporphyrin is important in humans

Answer 11

Type III

Question 12

Which type of cells cannot synthesize heme

Answer 12

Red blood cells

Question 13

What is the rate limiting enzyme of heme synthesis in the liver

Answer 13

delta- aminolevulinic acid synthase

Question 14

What is the enzyme delta- aminolevulinic acid synthase inhibited by

Answer 14

Heme

Question 15

In heme synthesis, which reaction requires pyridoxal phosphate (vitamin B6)

Answer 15

Conversion of glycine and succinyl coA to delta- aminolevulinic acid synthase

Question 16

Which two reactions in heme synthesis are inhibited by heavy metal poisoning (eg. lead)

Answer 16

1. Conversion of delta- aminolevulinic acid synthase to porphobilinogen
2. Conversion of protoporphyrin IX to Heme

Question 17

Which two enzymes in heme synthesis are inhibited by heavy metal poisoning (eg. lead)

Answer 17

1. Aminolevulinic acid
   dehydratase
2. Ferrochelatase

Question 18

What are porphyrias

Answer 18

Accumulation of porphyrin-like precursors due to disruption in heme synthese

Question 19

How will the urine appear in individuals wit porphyrias

Answer 19

Red urine

Question 20

What is the name of the type of porphyrias caused by heavy metal (lead) poisoning

Answer 20

Acquired porphyrias

Question 21

Which type of porphyria is the most common

Answer 21

Porphyria cutanea tarda

Question 22

Which type of porphyria occurs when there is a disruption of the synthesis hydroxymethylbilane from porphobilinogen

Answer 22

Acute Intermittent Porphyria

Question 23

Which porphyria is associated with photosensitivity

Answer 23

Porphyria cutanea tarda

Question 24

Which porphyria, in severe cases, is associated with dark wine colored urine if it is left to stand

Answer 24

Acute intermittent porphyria

Question 25

Which two metabolic pathways require Vitamin B6 (pyridoxal phosphate)

Answer 25

Transamination during amino acid metabolism and during heme synthesis