Shared Cell Structures Across Domains

Steps:

• Recall eukaryotic cells contain nucleus, mitochondria, ER, and Golgi; bacterial cells have nucleoid, peptidoglycan wall, and plasmids.
• Identify structures absent in one type: nucleus and organelles in bacteria; peptidoglycan wall in most eukaryotes.
• List universal features: both have plasma membrane for boundary, ribosomes for protein synthesis, and cytoplasm as internal medium.
• Match labels: assume 1=ribosomes, 3=plasma membrane, 5=cytoplasm based on typical diagrams.

Why B is correct:

• Option B selects ribosomes, plasma membrane, and cytoplasm, which are defined as essential in both cell types per cell theory and ultrastructure studies.

Why the others are wrong:

• A includes 2 (likely nucleus, eukaryotic-only) and 4 (likely cell wall, bacterial-specific).
• C includes 4 (bacterial cell wall, absent in animal eukaryotes).
• D omits 1 (ribosomes, present in both for translation).

Final answer: B