Which of the following has amide links

Options

A. Protein
B. Nylon
C. Peptide
D. All of these

Explanation

To determine which of the given options contains amide links, we need to understand what an amide linkage is and where it is found.

### Step-by-Step Solution:

1. **Understanding Amide Linkage**:
- An amide linkage is characterized by the presence of a carbonyl group (C=O) directly bonded to a nitrogen atom (N). The general structure can be represented as R1C(=O)NR2R3, where R1, R2, and R3 can be hydrogen atoms or hydrocarbon chains.

2. **Analyzing the Options**:
- **Option 1: Proteins**:
- Proteins are polymers made up of amino acids. The bond formed between the amino group of one amino acid and the carboxyl group of another amino acid is an amide bond (also known as a peptide bond). Therefore, proteins contain amide linkages.

- **Option 2: Nylon**:
- Nylon is a synthetic polymer made from the condensation of diamines and dicarboxylic acids. The linkage formed in nylon is also an amide bond. Thus, nylon contains amide linkages.

- **Option 3: Peptides**:
- Peptides are short chains of amino acids linked together by peptide bonds, which are indeed amide linkages. Therefore, peptides also contain amide linkages.

- **Option 4: All of these**:
- Since proteins, nylon, and peptides all contain amide linkages, this option is correct.

3. **Conclusion**:
- Based on the analysis, all the given options (proteins, nylon, and peptides) contain amide linkages. Therefore, the correct answer is **Option 4: All of these**.

### Final Answer:
All of these (proteins, nylon, and peptides) have amide links.