Porphyrins | Heme b Biosynthesis and its Regulation

The video explains heme biosynthesis, highlighting its role as a key porphyrin and iron-containing coenzyme in various biological processes. It details the pathways for synthesizing delta aminolevulinic acid (Ala) in eukaryotes and bacteria, and the conversion of Ala to heme through a series of enzymatic reactions. The localization of these enzymes in cellular compartments like mitochondria and cytoplasm is discussed, along with the regulation of heme synthesis, focusing on the role of Ala synthase and feedback mechanisms.

What is the primary role of heme in biological systems?

• It acts as a structural component in cell membranes.

• It functions as a hormone in the body.

• It is a primary energy source for cells.

• It serves as a coenzyme in various enzymes and proteins.

Which molecule is the starting material for heme synthesis?

• Succinyl CoA

• Glycine

• Delta aminolevulinic acid (Ala)

• Glutamyl tRNA

In higher order eukaryotes, which enzyme is responsible for the synthesis of Ala?

• Ala dehydratase

• Ala synthase

• Ferrochelatase

• Porphobilinogen synthase

What is the product formed when two molecules of Ala are condensed?

• Hydroxymethyl bilane

• Protoporphyrin IX

• Porphobilinogen

• Uroporphyrinogen III

Which enzyme is responsible for converting hydroxymethyl bilane into uroporphyrinogen III?

• Copro porphyrin oxidase

• Uroporphyrinogen decarboxylase

• Porphobilinogen deaminase

• Uroporphyrinogen III synthase

What is the role of ferrochelatase in heme synthesis?

• It removes carboxyl groups from uroporphyrinogen III.

• It converts porphobilinogen to hydroxymethyl bilane.

• It inserts iron into protoporphyrin IX.

• It condenses Ala molecules.

Where does the initial step of heme synthesis occur in the cell?

• Mitochondria

• Cytoplasm

• Endoplasmic reticulum

• Nucleus

What is the main regulatory point in the heme synthesis pathway?

• Ala synthase

• Porphobilinogen deaminase

• Uroporphyrinogen III synthase

• Ferrochelatase

How does heme regulate its own synthesis?

• By promoting ferrochelatase activity

• By increasing glucose levels

• By inhibiting Ala synthase

• By activating Ala synthase

Which condition can induce the production of heme due to its role in oxygen transport?

• Hyperthermia

• Dehydration

• Hypoxia

• Hyperglycemia