Read the following text and answer the question on the basis of the same:
DNA, a long polymer of deoxyribonucleotide. These substances to be acidic hence the named nucleic acid. The basic unit of DNA is a nucleotide which has three components a nitrogenous base, a pentose sugar (deoxyribose) and a phosphate group. There are two types of nitrogenous bases in DNA, Purine and Pyrimidine. J. Watson and E. Crick proposed a double helix model for the structure of DNA. There are four types of DNA i.e., A, B, C, Z.
Heaviest molecule of protoplasm is:

Options

A. Lipids
B. Proteins
C. DNA
D. RNA

Explanation

To answer the question, "Heaviest molecule of protoplasm is:", we will analyze the information provided in the text regarding the components of DNA and compare them to other biological macromolecules.

### Step-by-Step Solution:

1. **Identify the Components of DNA**:
- The text states that DNA is a long polymer made of deoxyribonucleotides. Each nucleotide consists of three components: a nitrogenous base, a pentose sugar (deoxyribose), and a phosphate group.

2. **Understand the Types of Nitrogenous Bases**:
- There are two categories of nitrogenous bases mentioned: purines and pyrimidines. This classification is important for understanding the structure of DNA but does not directly relate to the question about the heaviest molecule.

3. **Review the Structure of DNA**:
- The double helix model proposed by Watson and Crick indicates that DNA is a complex structure formed by the bonding of nucleotides. This complexity contributes to its overall mass.

4. **Compare DNA with Other Macromolecules**:
- The question asks for the heaviest molecule in protoplasm, and the options given are lipids, proteins, DNA, and RNA.
- DNA is known to have a very high molecular weight, often exceeding one million daltons due to its long chain of nucleotides.

5. **Conclusion**:
- Based on the information provided, DNA is identified as the heaviest molecule among the options listed. Therefore, the correct answer is **DNA**.

### Final Answer:
The heaviest molecule of protoplasm is **DNA**.

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