Cyclic peptide chain is present in ?
**Core Concept**
The question is testing knowledge of cyclic peptide chains, which are a type of peptide bond formed between two amino acids. This concept is crucial in understanding various biological processes, including protein structure and function.
**Why the Correct Answer is Right**
Cyclic peptide chains are present in certain antibiotics, such as Penicillins and Cephalosporins. These antibiotics contain a beta-lactam ring, which is a cyclic peptide chain that inhibits cell wall synthesis in bacteria. The beta-lactam ring is a key feature of these antibiotics, and its structure is essential for their mechanism of action.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a specific enough answer. While many proteins and peptides contain cyclic structures, not all of them are cyclic peptide chains.
**Option B:** This option is incorrect because it refers to a different type of compound altogether. Peptide bonds are indeed present in proteins, but the question specifically asks about cyclic peptide chains.
**Option C:** This option is incorrect because it is a general term that encompasses many different types of compounds. While some peptides may be cyclic, not all peptides are cyclic peptide chains.
**Clinical Pearl / High-Yield Fact**
A key feature of beta-lactam antibiotics is their ability to inhibit cell wall synthesis in bacteria. This is due to their cyclic peptide chain, which binds to penicillin-binding proteins (PBPs) and inhibits the cross-linking of peptidoglycan.
**Correct Answer:** D.