Biology (5090)
Cell membrane: Controls what enters and leaves the cell (selectively permeable) Cytoplasm: Jelly-like substance where chemical reactions happen Nucleus: Contains DNA, controls cell activities Mitochondria: Where respiration happens (produces energy) — the "powerhouse" Ribosomes: Where proteins are made
Cell wall: Made of cellulose, gives rigid structure and support Chloroplasts: Contain chlorophyll for photosynthesis (only in green parts) Large central vacuole: Contains cell sap, keeps cell turgid (firm)
Red blood cells: No nucleus, biconcave shape — more surface area for oxygen Root hair cells: Long extension increases surface area for water absorption Nerve cells: Very long to carry electrical signals quickly Sperm cells: Tail for swimming, lots of mitochondria for energy
Topic 1 of 4Cambridge O Levels
Cell Structure
The building blocks of all living things
All living things are made of cells — they are the basic units of life.
Animal Cell Components:
Plant Cells have everything animal cells have PLUS:
Specialised Cells:
Cell Organisation:
Cells → Tissues → Organs → Organ Systems → Organism
Key Points to Remember
- 1Plant cells have cell wall, chloroplasts, and large vacuole (animal cells don't)
- 2Mitochondria = energy production (respiration)
- 3Chloroplasts = photosynthesis (only in plant cells)
- 4Cells → Tissues → Organs → Organ Systems → Organism
Pakistan Example
Wheat Crop Cells in Punjab
Pakistan is one of the world's largest wheat producers, and Punjab's wheat fields depend on cell biology. Each wheat leaf cell contains chloroplasts that carry out photosynthesis, converting sunlight + CO₂ + water into glucose. The cell wall gives wheat stalks their rigidity to stand tall. Root hair cells have long extensions to absorb water from Punjab's irrigated canal system. When farmers say the crop is 'healthy,' they're really saying the cells are functioning well — turgid vacuoles, active chloroplasts, and efficient mitochondria!