Organisation of Cells (Cambridge International IGCSE Biology)
Exam board Cambridge International · IGCSEUpdated 2026-09-02
Producing new cells
Spec point —
2.1.2· State that new cells are produced by division of existing cells
- The cells in the body need to divide so that the body can grow and repair itself
- Cells grow and divide over and over again
- New cells are produced by the division of existing cells
Specialised cells
Spec point —
2.1.2· State that specialised cells have specific functions, limited to: (a) ciliated cells – movement of mucus in the trachea and bronchi (b) root hair cells – absorption (c) palisade mesophyll cells – photosynthesis (d) neurones – conduction of electrical impulses (e) red blood cells – transport of oxygen (f) sperm and egg cells (gametes) – reproduction
Specialised cells
Specialised cells in animals and plants
- Specialised cells are those which have developed certain characteristics in order to perform particular functions. These differences are controlled by genes in the nucleus
- Cells specialise by undergoing differentiation: this is a process by which cells develop the structure and characteristics needed to be able to carry out their functions
Specialised cells in animals table
| Cell | Function | Adaptations |
|---|---|---|
| Ciliated cell | Movement of mucus in the trachea and bronchi | - Extensions of the cytoplasm at the surface of the cell form hair-like structures called cilia, which beat to move mucus and trapped particles up to the throat |
| Nerve cell | Conduction of impulses | - Long so that nerves can run to and from different parts of the body to the central nervous system The cell has extensions and branches so it can communicate with other nerve cells, muscles and glands The axon (extension of cytoplasm away from the cell body) is covered with a fatty sheath, which insulates the nerve cell and speeds up the nerve impulse |
| Red blood cell | Transport of oxygen | - Biconcave disc shape increases surface area for more efficient diffusion of oxygen Contains haemoglobin, which joins with oxygen to transport it Contains no nucleus, increasing the amount of space available for haemoglobin inside the cell |
| Sperm cell | Reproduction | - The head contains the genetic material for fertilisation in a haploid nucleus (containing half the normal number of chromosomes) The acrosome in the head contains digestive enzymes so that a sperm can penetrate an egg The mid-piece is packed with mitochondria to release energy needed to swim and fertilise the egg The tail enables the sperm to swim |
| Egg cell (ovum) | Reproduction | - Contains a lot of cytoplasm, which has nutrients for the growth of the early embryo Haploid nucleus contains the genetic material for fertilisation Cell membrane changes after fertilisation by a single sperm so that no more sperm can enter |
Diagrams of specialised cells in animals
Ciliated cell
Nerve cell
Red blood cells
Sperm cell
Egg cell
Specialised cells in plants table
| Cell | Function | Adaptations |
|---|---|---|
| Root hair cell | Absorption of water and mineral ions from soil | - Root hair increases surface area of the cell to ensure maximum absorption of water and mineral ions - Walls are thin to ensure water moves through quickly - No chloroplasts present |
| Xylem vessel | Conduction of water through the plant, support of the plant | - No top and bottom walls between xylem vessels, so there is a continuous column of water running through them - Cells are dead and lack organelles and cytoplasm, allowing free passage of water - Walls are thickened with a substance called lignin, which provides additional structural support to the plant |
| Palisade mesophyll cell | Photosynthesis | - Column-shaped to maximise absorption of sunlight and to allow as many cells as possible to fit in a layer under the upper epidermis of the leaf - Packed with chloroplasts for maximum photosynthesis |
Diagrams of specialised cells in plants
Root hair cell
Xylem structure
Palisade mesophyll cell
Levels of organisation in an organism
Spec point —
2.1.2· Describe the meaning of the terms: cell, tissue, organ, organ system and organism as illustrated by examples given in the syllabus
| Level | Description |
|---|---|
| Cells | Basic functional and structural units of all living organisms |
| Tissues | Groups of cells of similar structure working together to perform the same function |
| Organs | Made from different tissues working together to perform specific functions |
| Organ systems | Groups of organs with related functions, working together to perform body functions |
Levels of organisation
Examples of systems in animals and plants
| System | Organs | Tissue examples |
|---|---|---|
| Digestive system | - Oesophagus - Stomach - Small intestine - Large intestine | - Muscle - Connective - Nerve - Epithelial |
| Circulatory system | - Heart - Veins - Arteries | - Muscle - Connective - Nerve - Epithelial |
| Immune system | - Thymus - Spleen | - Bone marrow |
| Respiratory system | - Trachea - Bronchi - Lungs | - Connective - Muscle - Epithelial |
| Excretory system | - Liver - Kidney - Skin, - Lungs | - Muscle - Connective - Nerve - Epithelial |
| Nervous system | - Brain - Spinal cord | Nerve |
| Reproductive system | - Ovary - Cervix - Uterus Vagina - Testes - Penis | - Muscle - Connective - Nerve - Erectile |
| Shoot system | - Leaf - Stem, - Flower - Fruit | - Epidermis - Mesophyll, - Xylem - Phloem |
| Root system | - Root, - Tuber | - Xylem - Phloem - Ground tissue |
Exam Hint
- Your syllabus states that you should be able to identify the different levels of organisation in drawings, diagrams and images of familiar material
- An example of this is shown in the exam question below:
The answer is B
- The correct answer is B, because a leaf is an organ (arrow 1), arrow 2 is pointing to a palisade mesophyll cell, and arrow 3 is pointing to the layer of spongy mesophyll cells (which is a tissue)
- Most incorrect answers here come from not being able to identify a tissue, so it’s worth making sure you understand and remember that tissues are always made up of only one type of cell.
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