Which statement best describes a key difference between archaea and bacteria?

• A. Archaea have peptidoglycan cell walls, whereas bacteria have protein-only cell walls.
• B. Archaea are always multicellular, whereas bacteria are always unicellular.
• C. Archaea have membrane lipids with ether linkages, whereas bacteria typically have ester-linked membrane lipids.
• D. Archaea lack ribosomes, whereas bacteria have 70S ribosomes.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the structural and biochemical differences between archaea and bacteria, focusing on cell wall composition, membrane lipids, cellular organization, and ribosome presence.
2. Step 2: Recall that bacteria typically have cell walls containing peptidoglycan, a polymer that provides structural support, while archaea do not have peptidoglycan but may have other cell wall types such as pseudopeptidoglycan or protein-based walls.
3. Step 3: Recognize that both archaea and bacteria are generally unicellular organisms, so the statement about multicellularity is incorrect.
4. Step 4: Consider membrane lipid chemistry: archaea have unique membrane lipids with ether linkages between glycerol and their hydrophobic side chains, whereas bacteria have ester linkages in their membrane lipids. This is a fundamental biochemical difference.
5. Step 5: Note that both archaea and bacteria possess ribosomes, typically 70S in size, so the statement about archaea lacking ribosomes is false.