Question

Differentiate between prosthetic groups and coenzymes. Give one example of each.

Answer 1

Hint: Prosthetic groups and coenzymes are the cofactors that bind with the enzyme to make it catalytically active. Cofactors are the non proteinaceous groups essential for the complete and proper functioning of an enzyme.

Complete answer:

Property	Prosthetic Group	Coenzyme
Nature	Organic molecules or metal ions complexed with organic molecules.	Organic molecules
Binding with apoenzyme	Always tightly bound to the apoenzyme.	Associated with apoenzyme only during catalysis.
Example	Haem in catalase and peroxidase, Metal ions such as Cu, Co, Zn, Mn.	FAD (flavin adenine dinucleotide), NAD(nicotinamide adenine dinucleotide )

Additional Information:
Enzymes are composed of one or more polypeptide chains ( except Ribozymes which are RNA molecules with catalytic ability). Most of the enzymes require non-protein groups for their biological activity. These are called cofactors. The protein portion of the enzyme is called an apoenzyme, which is generally inactive. The complete, biologically active conjugated enzyme (apoenzyme + cofactor) is referred to as holoenzyme.
Coenzymes act as carriers of chemical groups or atoms or electrons. They transport substrates from their point of generation to their point of utilization. For example, coenzyme NAD is involved in oxidation-reduction reactions of glycolysis and citric acid cycle in respiration, where it shuffles between its two forms- NAD+ is the oxidized form and NADH is the reduced form.
The Haem prosthetic group in catalase is a part of the active site of the enzyme and without it, the enzyme can not catalyze the hydrolysis of H₂O₂ to H₂O and O₂. Hydrogen Peroxide is a toxic product that needs to be eliminated from a cell. This enzyme is primarily found in peroxisomes. Peroxisomes are organelles observed in all eukaryotic cells.

Note: Haem is also present in hemoglobin where it binds with oxygen atoms. Hemoglobin is a protein involved in the transport of oxygen. It exists in erythrocytes(RBCs or red blood cells). Anemia is a type of medical condition wherein the level of hemoglobin or RBCs is lower than the normal body count.