Topic Summary: Cell Structure

Key Terms

• Cell: Basic unit of life; smallest structure capable of all life processes
• Organelle: Specialised structure within a cell with a specific function
• Prokaryotic: Cell type with no true nucleus; DNA free in cytoplasm (e.g. bacteria)
• Eukaryotic: Cell type with a true membrane-bound nucleus (e.g. animal, plant, fungal cells)
• Magnification: Number of times larger an image is than the real object
• Resolution: Ability to distinguish two separate points as distinct structures

Must-Know Facts

• All cells share: cell membrane, cytoplasm, ribosomes, genetic material (DNA)
• Prokaryotic cells are 1–5 μm; eukaryotic cells are 10–100 μm
• Plant cells have cell wall (cellulose), chloroplasts, and permanent vacuole — animal cells do not
• Bacterial cells have plasmids (small rings of DNA) and may have flagella
• Red blood cells have no nucleus — more space for haemoglobin
• Mitochondria are the site of aerobic respiration in ALL living cells, including plant cells
• Ribosomes are found in ALL cell types (prokaryotic and eukaryotic)
• Specialised cells are adapted in structure to match their function

Key Formulas

• Magnification = Image size ÷ Real size
• Real size = Image size ÷ Magnification
• Image size = Magnification × Real size

Unit conversions (scale):

• 1 mm = 1,000 μm (× 1,000 to convert mm → μm)
• 1 μm = 1,000 nm (× 1,000 to convert μm → nm)
• 1 mm = 1 × 10⁻³ m
• 1 μm = 1 × 10⁻⁶ m
• 1 nm = 1 × 10⁻⁹ m

Quick Reference: Cell Types

Feature	Animal	Plant	Bacterial
Nucleus	Yes	Yes	No
Cell membrane	Yes	Yes	Yes
Cell wall	No	Yes (cellulose)	Yes (not cellulose)
Mitochondria	Yes	Yes	No
Chloroplasts	No	Yes	No
Permanent vacuole	No	Yes	No
Ribosomes	Yes	Yes	Yes (smaller)
Plasmids	No	No	Yes