Problem 131 - Objective Biology for NEET

Question

Haem is a prosthetic group of enzyme (a) Peroxidase (b) Catalase (c) Both (a) and (b) (d) None of these

Step-by-Step Solution

Answer

The answer is (c) Both (a) and (b). Haem is a prosthetic group of both enzymes, peroxidase and catalase.

Step 1: Understanding Haem

Before answering the question, it is important to understand what Haem is. Haem is a complex organic molecule that contains an iron ion (Fe2+) held in a heterocyclic ring, known as a porphyrin. This prosthetic group plays significant roles in various biological processes.

Step 2: Haem and Peroxidase

Peroxidase is a type of enzyme that often leverages the properties of its prosthetic group, Haem. Peroxidases catalyze the conversion of hydrogen peroxide into water and molecular oxygen, which is an oxidation process that involves the Fe2+ ion of the Haem group. Therefore, Haem is a prosthetic group for peroxidase.

Step 3: Haem and Catalase

Similar to peroxidase, catalase is also an enzyme that decomposes hydrogen peroxide. It utilizes the iron atom of its prosthetic group, Haem, in the process. Therefore, Haem is also a prosthetic group for catalase.

Key Concepts

Haem

Haem is a vital component in many biological systems. It is a complex organic molecule encompassing an iron ion (Fe\(^{2+}\)) situated at the core of a heterocyclic structure known as a porphyrin. This arrangement allows haem to serve as a key player in oxygen binding and transport. The presence of iron is crucial, enabling haem to partake in redox reactions, which involve the transfer of electrons. Such reactions are essential in energy production and detoxification of cells. Moreover, haem is a prosthetic group, potentially pairing with various enzymes to enhance their functions.

Peroxidase

Peroxidase is an enzyme that employs haem as its prosthetic group to accelerate chemical reactions. This enzyme specifically catalyzes the breakdown of hydrogen peroxide (H\(_2\)O\(_2\)) into water and oxygen. This process is vital because it helps protect cells from damage caused by hydrogen peroxide, which can be a harmful byproduct of metabolism. During this reaction, the iron in the centre of the haem group goes through changes in its oxidation states. This ability allows peroxidase to effectively carry out its role in maintaining cellular health by combating oxidative stress.

Catalase

Catalase is another enzyme that utilizes haem as its prosthetic group. Its primary function is to decompose hydrogen peroxide into water and oxygen efficiently and rapidly. This particular enzyme is incredibly efficient, able to convert millions of molecules of hydrogen peroxide each second. Like peroxidase, catalase operates using the iron ion within haem, which facilitates its activity. By mitigating the accumulation of hydrogen peroxide, catalase plays a protective role in cells, preventing potential oxidative injuries that might otherwise damage cellular components.

Prosthetic Group

A prosthetic group is a non-polypeptide unit that tightly and permanently associates with a protein. It is crucial for the biological activity of the protein it is bound to. In the context of enzymes, prosthetic groups such as haem significantly enhance enzymatic activity. They may be involved in the enzyme's catalytic function, often participating directly in the enzyme's chemical reaction. These groups differ from cofactors that are not as firmly bound. The stable presence of prosthetic groups in enzymes like peroxidase and catalase underscores their indispensable role in maintaining proper enzyme functionality and thus, overall cellular processes.