units of proteins which unite in long chains to form proteins are called

Options

A. Sugar
B. Purines
C. pyrmidines
D. Amino acids

Answer

To answer the question "units of proteins which unite in long chains to form proteins are called," we will analyze the options provided and arrive at the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the basic units that combine to form proteins.

2. **Evaluating Options**:
- **Option 1: Sugar**: Sugars are carbohydrates and do not relate to proteins. Therefore, this option is incorrect.
- **Option 2: Purine**: Purines are nitrogenous bases found in DNA and RNA, not proteins. This option is also incorrect.
- **Option 3: Pyrimidine**: Similar to purines, pyrimidines are also nitrogenous bases found in DNA and RNA. This option is incorrect as well.
- **Option 4: Amino Acids**: Amino acids are organic compounds that contain both an amino group and a carboxylic group. They are the building blocks of proteins. Proteins are macromolecules made up of these amino acid monomers, which are linked together by peptide bonds.

3. **Conclusion**: Since amino acids are the units that combine in long chains to form proteins, the correct answer is **amino acids**.

### Final Answer:
The units of proteins which unite in long chains to form proteins are called **amino acids**.

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