Organisation of Cells (Cambridge O Level Biology)

Specialised cells in animals

• Specialised cells are those which have developed certain characteristics in order to perform specific 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	Adaptation
Ciliated cell	Movement of mucus in the trachea and bronchi of the chest cavity	Hair-like structures form on the surface of the cell called cilia These beat to move mucus and trapped particles up and out of the trachea
Nerve cell	Conduction of impules	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 for communication. The axon is insulated for speed of transmission of the nerve impulse
Red blood cell	Transport of oxygen	Biconcave disc shape increases surface area for more efficient diffusion of oxygen Contains haemoglobin for to carry oxygen No nucleus to increase space for carrying oxygen
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 the sperm cell can penetrate the egg cell The mid-piece has many mitochondria to provide energy for tail movement
Egg cell	Reproduction	Contains a lot of cytoplasm which has nutrients for the growth of the early embryo Haploid nucleus contains genetic material for fertilisation Cell membrane changes after fertilisation by a single sperm cell so no more sperm can enter

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Diagrams of specialised cells in animals

Ciliated cell

Nerve cell

Red blood cells

Sperm cell

Egg cell

Specialised Cells in Plants Table

Cell	Function	Adaptation
Root hair cell	Absorption of water and minerals from soil	Root hair increases the surface area to ensure maximum absorption of water and minerals Walls are thin to ensure water moves through quickly No chloroplast present as no light underground
Xylem vessel	Conduction of water through the plant; provides support for the plant	No top or bottom cell walls for continuous flow of water Cells are dead so no organelles to ensure a smooth stream of water can flow Thickened cell walls with lignin to provide structural support
Palisade mesophyll cell	Photosynthesis	Column shaped to maximise absorption of sunlight Contains many chloroplasts for maximum photosynthesis

Diagrams of specialised cells in plants

Root hair cell

Xylem structure

Palisade mesophyll cell

Level	Description
Cells	Basic functional and structural units in a living organism
Tissues	GRoups of cells of similar structure working together to perform the same function
Organs	Made from different tissues working together to perform a specific function
Organ systems	Groups of organs with related functions working together to perform body functions

Levels of organisation diagram

An example of the different levels of organisation

Levels of Organisation Examples Table

Organ system	Organ	Tissue
Shoot system	Leaf, stem, flower, fruit	Epidermis mesophyll Xylem Phloem
Root system	Root, tuber	Xylem Phloem Ground tissue
Digestive system	Oesophagus, stomach, small and large intestines	Muscle Connective Nerve Epithelial
Circulatory system	Heart, arteries, veins	Muscle Connective Nerve Epithelial
Immune system	Thymus, spleen	Bone marrow
Respiratory system	Trachea, bronchi, lungs	Muscle Connective Nerve Epithelial
Excretory system	Liver, kidney, skin, lungs	Muscle Connective Nerve Epithelial
Nervous system	Brain , spinal cord	Nerve
Reproductive system	Ovary, uterus, vagina, penis, testes	Muscle Connective Nerve Epithelial