IGCSEBiologyCambridge (CIE)Revision Notes2. Organisation of the OrganismCell Structure & Size of SpecimensOrganisation of Cells

Organisation of Cells (Cambridge (CIE) IGCSE Biology): Revision Note

Exam code: 0610 & 0970

Written by: Lára Marie McIvor

Reviewed by: Jenna Quinn

Updated on 24 August 2026

Producing new cells

The cells in the body need to divide so that the body can grow and repair (opens in a new tab) itself
Cells grow and divide over and over again
New cells are produced by the division of existing cells

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

Diagram of two ciliated epithelial cells showing labelled cilia moving mucus, with labels showing the cell membrane, cytoplasm, nucleus and mitochondria — **Ciliated cell**

Diagram of a motor neurone showing the dendrites, cell body with nucleus and ribosomes, axon with myelin sheath and cytoplasm, and a branched nerve ending — **Nerve cell**

Diagram of two red blood cells showing their characteristic biconcave shape without nucleus, cytoplasm containing haemoglobin and the cell membrane — **Red blood cells**

Diagram of a human sperm cell labelled with head containing the acrosome and the nucleus, the mitochondria in the mid-piece, and the long tail or flagellum. The cytoplasm and cell membrane (present throughout) are also labelled. — **Sperm cell**

Diagram of a human egg cell labelled with follicle cells, zona pellucida, cell membrane, cytoplasm, nucleus, mitochondria and yolk droplets — **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

Diagram of a plant root hair cell labelled with cell wall, cell membrane, cytoplasm, vacuole, nucleus, mitochondrion, ribosomes and the root hair extension — **Root hair cell**

Diagram of a xylem vessel showing lignin-thickened walls, hollow dead cells formed from broken-down cell walls which contain no typical cell structures , forming a continuous water column. — **Xylem structure**

Diagram of a palisade mesophyll cell showing the cell wall, cytoplasm, nucleus, ribosomes, chloroplasts, mitochondria and a large central vacuole — **Palisade mesophyll cell**

Levels of organisation in an organism

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

Diagram showing biological organisation as exemplified by a heart muscle cell, heart muscle tissue, the heart organ, circulatory system in a deer, then the whole deer organism. — **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

Examiner Tips and Tricks

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:

Typical levels of organisation question, IGCSE & GCSE Biology revision notes

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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