Question 1

What is the main structural difference between archaea and eubacteria?

Accepted Answer

Archaeal cell walls have different chemistry and do not contain bacterial peptidoglycan. Archaeal membranes contain branched-chain lipids, while eubacterial membranes have a different lipid composition. Both are prokaryotic and lack a membrane-bound nucleus.

Question 2

How are cyanobacteria different from eukaryotic photosynthetic organisms?

Accepted Answer

Cyanobacteria are prokaryotic photosynthetic autotrophs within the eubacterial forms. They use chlorophyll a and phycobilins in thylakoid membranes, but they do not have chloroplasts or grana. Their photosynthetic lamellae are parallel and are not organized into grana.

Question 3

Why is mycoplasma pleomorphic?

Accepted Answer

Mycoplasma are eubacterial forms that lack a rigid cell wall. Without the wall, the cell can change shape, which is called pleomorphism. They are among the smallest living cells.

Question 4

Why are beta-lactam antibiotics ineffective against mycoplasma?

Accepted Answer

Beta-lactams inhibit synthesis of the peptidoglycan cell wall. Mycoplasma do not possess this wall, so the antibiotic has no peptidoglycan target. This is an intrinsic resistance associated with wall synthesis, not resistance to every antibiotic.

Question 5

What is the defining prokaryotic feature shared by Monera?

Accepted Answer

Monera are prokaryotic: they lack a membrane-bound nucleus and membrane-bound organelles. Their genetic material is located in a nucleoid region rather than inside a nuclear membrane.

Monera Up Close — Archaea and Eubacterial Forms: Cyanobacteria, Mycoplasma

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