Question

The largest biomolecule in a living cell is

• A. Glycogen
• B. Protein
• C. Cholesterol
• D. Deoxyribonucleic acid

Hint:

Macromolecular Scale: Chromosomal DNA ($10^{11}\text{ Da}$) $\gg$ Glycogen ($10^8\text{ Da}$) $\gg$ Giant Proteins ($10^6\text{ Da}$) $\gg$ Lipids ($< 10^3\text{ Da}$).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Chromosomal DNA polymers possess unbroken continuous nucleotide lengths with molecular weights reaching hundreds of billions of Daltons.
Key Formula or Approach:
\[ \text{MW of Human Chromosome 1 DNA} \approx 249 \times 10^6\text{ bp} \times 660\text{ Da/bp} \approx 1.6 \times 10^{11}\text{ Daltons} \]

Step 2: Detailed Explanation:
Evaluating macromolecular sizes:
1. Deoxyribonucleic Acid (DNA): A single intact genomic DNA molecule in a eukaryotic chromosome consists of tens to hundreds of millions of base pairs (e.g., human chromosome 1 has 249 million base pairs, MW $\approx 1.6 \times 10^{11}\text{ Da}$), making it by far the single largest biomolecule in any living cell.
2. Proteins: Largest protein titin has MW $\approx 3.8 \times 10^6\text{ Da}$.
3. Glycogen: Particle MW up to $10^7 - 10^8\text{ Da}$.
4. Cholesterol: Small lipid molecule (MW $386.6\text{ Da}$).

Step 3: Final Answer:
Therefore, the largest biomolecule in a living cell is Deoxyribonucleic acid, matching option (D).