Which of the following statements about prosthetic groups is INCORRECT?
A. Prosthetic groups form an integral part of the secondary structure of proteins.
B. Heme is an example of a prosthetic group.
C. Prosthetic groups increase the inherent chemical reactivity of proteins.
D. Prosthetic groups are not amino acids.
E. All the above are correct.
The correct answer and explanation is:
The correct answer is A. Prosthetic groups form an integral part of the secondary structure of proteins.
Explanation:
A prosthetic group is a non-polypeptide unit that is tightly and permanently attached to a protein, and it plays a crucial role in the protein’s function. Prosthetic groups are typically organic molecules or metal ions that enhance the protein’s function. However, they are not part of the protein’s secondary structure.
- Prosthetic groups form an integral part of the secondary structure of proteins: This statement is incorrect. The secondary structure of proteins refers to the local folding patterns of the protein chain, such as alpha-helices and beta-pleated sheets. Prosthetic groups are not part of the polypeptide chain’s secondary structure. Instead, they are separate entities that bind to specific sites on the protein, often covalently, to enhance the protein’s activity.
- Heme is an example of a prosthetic group: This statement is correct. Heme is a prosthetic group that is found in proteins like hemoglobin and myoglobin. It contains an iron atom that is essential for binding oxygen. The heme group is tightly bound to the protein but does not form part of its polypeptide structure.
- Prosthetic groups increase the inherent chemical reactivity of proteins: This is also true. Prosthetic groups can enhance the chemical reactivity of proteins by providing additional functional groups or metal ions that can participate in reactions. For example, the iron in the heme group enables hemoglobin to bind oxygen, which would not be possible with just the polypeptide chain.
- Prosthetic groups are not amino acids: This statement is correct. Prosthetic groups are distinct from the amino acid residues that make up the polypeptide chain of the protein. They are often non-amino acid molecules, such as heme (which is a porphyrin derivative), flavin, or metal ions like zinc or iron.
In summary, prosthetic groups are vital for the function of many proteins, but they do not form part of the secondary structure of the protein. They are distinct from the amino acid chain and serve as essential functional components.