Cell Classification — What single criterion best distinguishes a prokaryotic cell from a eukaryotic cell?
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AWhether the organism is single-celled or multicelled
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BWhether the cell has a membrane-bound nucleus
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CWhether cytosol is present
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DWhether DNA is present in the cell
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EWhether the cell has ribosomes
Answer
Correct Answer: Whether the cell has a membrane-bound nucleus
Explanation
Introduction:Prokaryotes and eukaryotes are defined by internal compartmentalization. The most decisive differentiator is the presence of a membrane-bound nucleus in eukaryotes, which prokaryotes lack.
Given Data / Assumptions:
- Both groups contain DNA and ribosomes.
- Cytosol is universal in cellular life.
- Unicellularity vs multicellularity does not define the distinction (many eukaryotes are unicellular; some prokaryotes form multicellular-like colonies).
Concept / Approach:Identify the necessary and sufficient structural hallmark that separates the two domains: the nuclear envelope and complex endomembrane system of eukaryotes.
Step-by-Step Solution:
1) Option a: Lifestyle (uni vs multicellular) is not definitive.2) Option b: Presence of a membrane-bound nucleus is definitive for eukaryotes; this distinguishes them from prokaryotes.3) Option c: Cytosol exists in both; not distinguishing.4) Option d: DNA exists in all cells; not distinguishing.5) Option e: Ribosomes are present in both; not distinguishing.Verification / Alternative check:Taxonomic definitions: Eukarya possess a nuclear envelope; Bacteria and Archaea do not. This single structural criterion is standard in textbooks and courses.
Why Other Options Are Wrong:
a) Many eukaryotes are unicellular; criterion fails.c) Universal component; not diagnostic.d) DNA is universal; not diagnostic.e) Ribosomes are universal; not diagnostic.Common Pitfalls:Assuming complexity equals multicellularity; overlooking that ribosomes and DNA are universal to cellular life.
Final Answer:Presence of a membrane-bound nucleus.