Endosymbiotic Loss of Prokaryotic Cell Wall

Steps:

• Endosymbiotic theory states mitochondria originated from engulfed aerobic prokaryotes.
• Prokaryotes possess a cell wall for protection, absent in mature mitochondria.
• Mitochondria retain prokaryote-like features: circular DNA, 70S ribosomes, and inner membrane folds (cristae).
• Thus, the cell wall was lost during integration into the host cell.

Why A is correct:

• Mitochondria lack a cell wall, a defining prokaryotic structure for rigidity and shape, which was shed post-engulfment to allow symbiosis.

Why the others are wrong:

• B: Mitochondria maintain a circular chromosome, similar to prokaryotic DNA.
• C: Mitochondria developed internal membranes (cristae) from prokaryotic plasma membrane invaginations.
• D: Mitochondria contain 70S ribosomes for protein synthesis, akin to prokaryotes.

Final answer: A