Which one of the following does not differ in E.coli and Chlamydomonas?

Options

A. Cell wall
B. Cell membrane
C. Ribosomes
D. Chromosomal organization.

Answer

To determine which characteristic does not differ between E. coli and Chlamydomonas, we need to analyze the options provided:

1. **Cell Wall**:
- E. coli is a prokaryote and has a cell wall made of peptidoglycan.
- Chlamydomonas is a eukaryote and has a cell wall made of cellulose.
- Therefore, the cell wall differs between the two.

2. **Cell Membrane**:
- Both E. coli and Chlamydomonas have a cell membrane that is fundamentally similar in structure, composed of a phospholipid bilayer with embedded proteins.
- Thus, the cell membrane does not differ between the two organisms.

3. **Ribosomes**:
- E. coli has 70S ribosomes, which are characteristic of prokaryotes.
- Chlamydomonas has 80S ribosomes, typical of eukaryotes.
- Hence, ribosomes differ between the two.

4. **Chromosomal Organization**:
- E. coli has a single, circular chromosome.
- Chlamydomonas has multiple linear chromosomes.
- Therefore, chromosomal organization differs between the two.

After analyzing all the options, the characteristic that does not differ between E. coli and Chlamydomonas is the **cell membrane**.

### Final Answer:
The correct answer is **option 2: cell membrane**.