Question

which structure is unique to eukaryotic cells?
○ dna
○ cell membrane
○ ribosomes
○ nucleus

Explanation:

• DNA: Both prokaryotic and eukaryotic cells have DNA (prokaryotes have circular DNA in the nucleoid, eukaryotes have linear DNA in the nucleus), so not unique.
• Cell membrane: Both prokaryotic and eukaryotic cells have a cell membrane that controls the movement of substances in and out of the cell, so not unique.
• Ribosomes: Both prokaryotic and eukaryotic cells have ribosomes (though prokaryotic ribosomes are smaller, 70S, and eukaryotic are 80S), so not unique.
• Nucleus: Eukaryotic cells have a membrane - bound nucleus that encloses the genetic material. Prokaryotic cells do not have a nucleus; their genetic material is in the nucleoid region without a membrane. So the nucleus is unique to eukaryotic cells.

Answer:

D. nucleus