1.2 Specialised Cells, Tissues and Organs

2026 📋 Syllabus Objectives

By the end of these notes, you should be able to:

  1. Understand that cells can become specialised and that their structure is linked to their specific function — using examples from the syllabus.
  2. Understand the terms cell, tissue, organ, organ system, and organism — with examples for each.
  3. State and use the formula: magnification = image size ÷ actual size.

📖 Main Content

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1. What Is a Specialised Cell?

Every living organism starts from one or a few basic cells. As an organism grows, cells do not all stay the same — they change shape and structure so they can carry out a specific job. This process is called specialisation.

Think of it like workers in a factory. Not everyone does the same job — some pack boxes, some drive forklifts, some check quality. In the same way, different cells in your body are each built for a different role.

Key idea: A specialised cell has a structure (shape, size, parts) that is perfectly suited to the job it does.

2. Examples of Specialised Cells

Below are the main specialised cells you need to know for O Level Biology. For each one, learn: what it looks like → why it looks that way → what job it does.

🔴 Red Blood Cell (in humans)

Function: Carries oxygen around the body in the blood.

Specialised features and why:

  • Biconcave shape (disc-shaped, pinched in the middle on both sides) — this increases the surface area, so more oxygen can be absorbed quickly.
  • No nucleus — this leaves more space inside the cell to carry the oxygen-carrying protein called haemoglobin.
  • Very small and flexible — allows the cell to squeeze through tiny blood vessels called capillaries.
  • Packed full of haemoglobin — this red pigment binds to oxygen and carries it to all parts of the body.

💧 Sperm Cell (in males)

Function: Carries genetic information from the father and fertilises the egg cell.

Specialised features and why:

  • Long tail (flagellum) — allows the sperm to swim towards the egg cell.
  • Streamlined head — helps the sperm move easily through fluid.
  • Many mitochondria in the middle section — mitochondria release energy, and the sperm needs a lot of energy to swim long distances.
  • Acrosome (a cap on the head) — contains enzymes (chemicals) that break through the outer layer of the egg so the sperm can enter.

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