State that Archaea and Bacteria are prokaryotes and that there are differences between them, limited to differences in membrane lipids, ribosomal RNA and composition of cell walls

Sourav PanNovember 1, 2024

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Prokaryotic Domains: Archaea and Bacteria

Archaea and Bacteria are both classified as prokaryotes, meaning they lack a membrane-bound nucleus and other organelles. Despite this shared classification, there are significant differences between the two groups, particularly in three key areas: membrane lipids, ribosomal RNA, and cell wall composition.

1. Membrane Lipids

• Bacteria: The membranes of bacteria typically contain phospholipids composed of fatty acids linked to glycerol by ester bonds.
• Archaea: In contrast, archaeal membranes are made up of ether-linked lipids, which can include branched isoprenoid chains. This structural difference contributes to the stability of archaeal membranes, especially in extreme environments.

2. Ribosomal RNA

• Bacteria: The ribosomal RNA (rRNA) sequences in bacteria are distinct from those in archaea. Bacterial rRNA is part of the 70S ribosome, which includes 16S rRNA.
• Archaea: Archaeal rRNA also forms part of the 70S ribosome but has a different sequence and structure compared to bacterial rRNA. The 16S rRNA in archaea shows greater similarity to eukaryotic rRNA than to bacterial rRNA.

3. Composition of Cell Walls

• Bacteria: Most bacteria have cell walls composed of peptidoglycan, a polymer consisting of sugars and amino acids that provides structural support.
• Archaea: In contrast, archaeal cell walls do not contain peptidoglycan. Instead, they may be composed of pseudopeptidoglycan or other unique polymers such as polysaccharides or proteins.