Example 1
A cell has ribosomes and circular DNA but no nucleus. Classify it.
It is prokaryotic: absence of a membrane-bound nucleus and the DNA description support this classification.
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Year 11 · SACE Stage 1
Cell types and organelles
Match cell structures to functions and distinguish major cell types.
Method and worked examples
Prokaryotic and eukaryotic cells share a plasma membrane, hereditary nucleic acids, ribosomes and proteins. Prokaryotes lack a membrane-bound nucleus and other membrane-bound organelles; their main chromosome is usually circular. Eukaryotic cells have a nucleus and compartmentalised functions. Size alone is a clue, not a complete identification rule.
Ribosomes assemble proteins. Mitochondria carry out major stages of aerobic respiration; chloroplasts carry out photosynthesis. Endoplasmic reticulum and Golgi bodies help produce, modify and transport cell products. A large vacuole supports many plant cells. Plant cells have a cellulose wall outside the membrane, but some plant cells, including many root cells, lack chloroplasts.
Example 1
Example 2
A leaf cell has a wall, chloroplasts and a large vacuole. Which structure captures light energy?
Chloroplasts contain photosynthetic pigments and carry out photosynthesis; the wall mainly provides support.
Watch out: They lack membrane-bound organelles, but do contain ribosomes that assemble proteins.