LIFE SCIENCE

Detailed explanation-1: -Archaea have rigid cell walls with diverse structures. They contain many unusual lipids with repeating isoprenyl groups linked to glycerol and an S layer of glycoproteins in a lattice-like arrangement attached to the membrane.

Detailed explanation-2: -Some archaea lack a cell wall altogether. While it is not universal, a large number of Archaea have a proteinaceous S-layer that is considered to be part of the cell wall itself (unlike in Bacteria, where an S-layer is a structure in addition to the cell wall).

Detailed explanation-3: -Structurally, archaea are most similar to gram-positive bacteria. Most have a single plasma membrane and cell wall, and lack a periplasmic space; the exception to this general rule is Ignicoccus, which possess a particularly large periplasm that contains membrane-bound vesicles and is enclosed by an outer membrane.