Biology · Both
Cells & Organisation
Animal and plant cells, key organelles, specialised cells and how cells form tissues, organs and systems.
All living things are made of cells. You must know the structures of animal and plant cells, what each organelle does, and how specialised cells are adapted to their function.
Animal and plant cells
**Both animal and plant cells have:**
• Nucleus – controls the cell and contains DNA
• Cytoplasm – where chemical reactions happen
• Cell membrane – controls what enters and leaves
• Mitochondria – release energy by respiration
• Ribosomes – make proteins
**Plant cells also have:**
• Cell wall (cellulose) – supports and strengthens
• Chloroplasts – photosynthesis (contain chlorophyll)
• Permanent vacuole – stores cell sap, keeps cell turgid
Worked example
Name two structures found in plant cells but not in animal cells.
Solution
**Cell wall** and **chloroplasts** (also permanent vacuole).
Specialised cells
Cells are adapted to their job:
• **Red blood cell** – no nucleus, biconcave shape, haemoglobin → carries oxygen
• **Nerve cell (neurone)** – long axon, branched endings → transmits electrical impulses
• **Sperm cell** – tail (flagellum), many mitochondria, enzymes in head → swims to egg and fertilises
• **Root hair cell** – long extension → large surface area for water/mineral uptake
• **Palisade cell** – many chloroplasts, tall shape → maximises photosynthesis
Levels of organisation
Cell → Tissue → Organ → Organ system → Organism
Example: muscle cell → muscle tissue → heart → circulatory system → human
Practice questions
Try these without looking at the answers first.
Q1.Which organelle releases energy from glucose?
Show answer
Mitochondria
Q2.Why do red blood cells have no nucleus?
Show answer
More space for haemoglobin / to carry more oxygen
Q3.Name the level of organisation between tissue and organ system.
Show answer
Organ