Cell Structure, Organisation and Viruses
Comparing prokaryotic and eukaryotic ultrastructure, linking organelles to function, and placing acellular viruses in biological context.
How to study A-level Biology
Move between scales deliberately: identify the biological process, trace matter or information, use quantitative evidence, then evaluate the method and conclusion.
Core concepts
Concept 1
Prokaryotic and eukaryotic cells share core features but differ in compartmentalisation, DNA organisation and organelle structure.
Exam cue: Identify a structure from visible evidence before inferring its function.
Concept 2
Cell specialisation and organisation into tissues, organs and systems produce division of labour in multicellular organisms.
Exam cue: Compare like with like: DNA location, ribosome size, organelles and cell wall composition.
Concept 3
Viruses contain genetic material and protein but depend on host-cell machinery for replication.
Exam cue: Relate abundance of an organelle to the cell's energy, synthesis or transport demands.
Risk pitfalls and guardrails
Calling every cell wall cellulose.
Guardrail: Do not replace a mechanism with a vague purpose statement, or infer causation from an association without experimental support.
Treating viruses as prokaryotic cells.
Guardrail: Do not replace a mechanism with a vague purpose statement, or infer causation from an association without experimental support.
Listing organelles without connecting their structure to a cellular process.
Guardrail: Do not replace a mechanism with a vague purpose statement, or infer causation from an association without experimental support.
Memory anchors
Prokaryote
A prokaryote lacks a membrane-bound nucleus and membrane-bound organelles.
Eukaryote
A eukaryotic cell compartmentalises functions in membrane-bound organelles.
Rough ER
Rough endoplasmic reticulum synthesises and transports proteins using attached ribosomes.
Golgi Apparatus
The Golgi modifies and packages molecules into vesicles.
Virus
A virus is an acellular infectious agent that replicates only within host cells.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Which structure is found in both prokaryotic and eukaryotic cells?
Which observation identifies a cell as prokaryotic?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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