OCR AS Biology A – Foundations in
Biology (Module 2)
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2.1 Cell Structure
Cell Theory
All living organisms are made of cells
Cells are the basic unit of life
New cells arise from pre‑existing cells
Prokaryotic Cells (Bacteria)
No nucleus (DNA is circular and free in cytoplasm)
Cell wall made of peptidoglycan (murein)
Ribosomes: 70S (smaller)
May contain plasmids
No membrane‑bound organelles
Eukaryotic Cells
Contain membrane‑bound organelles and a true nucleus.
, Nucleus
Contains DNA as chromosomes
Controls cell activities
Mitochondria
Site of aerobic respiration
Inner membrane folded into cristae
Ribosomes
Site of protein synthesis
80S in eukaryotes
Endoplasmic Reticulum
RER: protein synthesis (ribosomes attached)
SER: lipid synthesis
Golgi Apparatus
Biology (Module 2)
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2.1 Cell Structure
Cell Theory
All living organisms are made of cells
Cells are the basic unit of life
New cells arise from pre‑existing cells
Prokaryotic Cells (Bacteria)
No nucleus (DNA is circular and free in cytoplasm)
Cell wall made of peptidoglycan (murein)
Ribosomes: 70S (smaller)
May contain plasmids
No membrane‑bound organelles
Eukaryotic Cells
Contain membrane‑bound organelles and a true nucleus.
, Nucleus
Contains DNA as chromosomes
Controls cell activities
Mitochondria
Site of aerobic respiration
Inner membrane folded into cristae
Ribosomes
Site of protein synthesis
80S in eukaryotes
Endoplasmic Reticulum
RER: protein synthesis (ribosomes attached)
SER: lipid synthesis
Golgi Apparatus
