Specialised cells are cells with features that enable them to carry out a specific function. 

1. Flattened, biconcave shape - increases the surface area to volume ratio for diffusion of oxygen
2. No nucleus or organelles - provides more space for haemoglobin
3. Flexible - can fit through narrow capillaries

1. Flexible cell membrane - allows the cell to engulf pathogens
2. Has many lysosomes containing digestive enzymes - break down engulfed particles
3. Multi-lobed nucleus - allows it to squeeze through small gaps to reach sites of infection

1. Has a flagellum - allows it to swim to an egg cell
2. Contains many mitochondria - supply energy for movement
3. Has an acrosome that contains digestive enzymes - allows the sperm cell to enter the egg cell

Squamous epithelial cells are very thin and permeable so that gases can diffuse easily. 

Ciliated epithelial cells have cilia that beat to move pathogens, mucus or egg cells. 

1. Contain lots of chloroplasts - absorb light for photosynthesis
2. Thin cell walls - allow carbon dioxide to quickly diffuse into the cell
3. Tall and thin shapes - the cells can pack closely together to from a continuous layer

1. Has a root hair - increases the surface area for absorption of materials
2. Thin, permeable cell wall - allows water and ions to enter the cell
3. Contains lots of mitochondria - provide energy for active transport

In the presence of light, guard cells absorb water to become turgid, which opens the stomata and allows carbon dioxide to diffuse into the leaf. 

When there is less water available, guard cells lose water and shrink, which closes the stomata to prevent excess water loss.