20 Questions
Which enzyme is the rate-limiting step in heme synthesis?
ALAS
Which cofactor is required by ALAS for heme synthesis?
Vitamin B6
Which isozyme of ALAS is expressed in erythroid cells?
ALAS2
Which enzyme condenses two molecules of ALA to form porphobilinogen (PBG)?
PBGD
Which enzyme converts protoporphyrinogen IX to protoporphyrin IX?
CPOX
Which enzyme directs the stereochemistry of the reaction to form uroporphyrinogen III?
UROS
Which porphyria is the most common?
Porphyria Cutanea Tarda
Which type of porphyria is characterized by increased synthesis of intermediates prior to the genetic block?
Hepatic porphyrias
Which type of porphyria is associated with photosensitivity?
Erythroid porphyrias
Which enzyme is inhibited by lead and can cause features similar to porphyrias?
ALA dehydratase
Which organelle is responsible for the synthesis of heme?
Mitochondria
What is the primary function of heme in the body?
Transport of oxygen
Which metal is chelated with the protoporphyrin IX ring to form heme?
Iron (Fe)
What is the main product of heme degradation?
Bilirubin
Which of the following is NOT a porphyria resulting from enzyme deficiencies in heme synthesis?
Hemochromatosis
What can heme rapidly autooxidize to?
Hemin (Fe3+)
Which step in heme synthesis is catalyzed by 5-aminolevulinic acid (δALA) synthase (ALAS)?
First step
How does lead poisoning affect heme biosynthesis?
Inhibits heme production
Which of the following is NOT a primary site of heme synthesis and catabolism?
Kidney
What can accumulating upstream intermediates in porphyrias be cytotoxic in the presence of?
Light and molecular oxygen
Test your knowledge on the biochemistry of blood and heme synthesis. Learn about the regulation of the rate-limiting step, connections to the TCA cycle and amino acid metabolism, and the role of iron. Discover how lead poisoning can impact heme biosynthesis and resemble porphyria.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
