Cell Specialisation & how they're adapted

Squamous Epithelial

-         Epithelium is often permeable and occurs where small molecules need to pass quickly through membranes via filtration or diffusion.

-         Many have a cilia.

Ciliated Epithelial

-         Cilia are tiny hair like structures on the surface of the cell. The hairs sweep hair, mucus, trapped dust and bacteria up to the back of the throat where it can be swallowed.

-         Beat together in a rhythm: moves mucus back up the trachea into the throat.

Xylem

-         Xylem cells: virtually no cytoplasm, organelles & end walls. Form a continuous tube in which H₂O passes freely.

-         Cell wall – strengthen by lignin, tough waterproof substance. Lignin deposited in walls, (spirals, annular or reticulate patterns) allows xylems to strength as plant grows – enables stem or branch to grow.

-         Made from dead cells aligned end to end to form a continuous column.

-         Tubes = narrow, so H₂O column doesn’t break easily & capillary action = effective.

-         Bordered pits in lignified walls allow H₂O movement. (Sideways from one vessel to another.)

The flow of water is not impeded, because:

-         No cross-walls.

-         No cell contents, nucleus or cytoplasm.

-         Lignin thickening prevents walls from collapsing.

Phloem

-         Companion cells have many mitochondria, which provide the energy needed for the companion cells to load sugars from the mesophyll cells into…