Question 1:
How much of the protein content makes an E.coli cell, in terms of the percentage of the total weight of the cell?
E. coli Protein Content Percentage
The correct answer to the question on E. coli protein content is (A) 15.0%, representing approximately 15% of the cell’s total wet weight. This value aligns with standard biochemical references for bacterial composition, where proteins dominate cellular mass.
Correct Answer: 15.0%
E. coli cells contain about 15% protein by total wet weight, crucial for enzymes, structure, and metabolism. Wet weight includes ~70-80% water, so protein mass is ~0.2 pg per 0.4 pg dry cell. This matches exam contexts and sources like Thermo Fisher data.
Why Other Options Are Incorrect
| Option | Value | Explanation |
|---|---|---|
| (B) | 5.0% | Too low for wet weight; underestimates proteins, which exceed lipids (~10%) and RNA (~3-5%). |
| (C) | 0.5% | Negligible; ignores proteins as major component (~half dry mass). |
| (D) | 30.0% | Overstates wet weight; closer to 52-55% of dry weight, not total (wet) weight. |
Cell Composition Context
Dry weight is ~55% protein, 20% RNA, 10% DNA/lipids, rest small molecules—but wet weight dilutes to ~15% protein due to water. Values vary slightly by growth phase, but 15% is standard for MCQs. For students in molecular biology, remember wet weight for total percentage queries.
