1. Extra cellular components Collagen microfibrils Image Credit: Fine structure of collagen circa 1948Fine structure of collagen circa 1948

2. The extracellular matrix Plant cell secrete cellulose and other carbohydrates Fungi and insect cells secrete chitin Bacteria secrete murin Animal cells secrete proteins (e.g. collagen) glycoproteins and other conjugated proteins © 2010 Paul Billiet ODWSODWS

3. Functions of extracellular matrix Mechanical, they give tissues strength and elasticity Protection against extracellular change and retention of water Control of cell behaviour by binding of growth factors and interaction with cell- surface receptors © 2010 Paul Billiet ODWSODWS

4. Animal tissues Image Credit; www.steve.gb.com/www.steve.gb.com/

5. THE PLANT CELL WALL The formation of a cell plate starts as soon as the nucleus has divided © 2010 Paul Billiet ODWSODWS

6. Cell plate to cell wall The cell plate becomes the middle lamella that glues the cells together New cell wall material is secreted either side of the middles lamella = primary cell wall (no cellulose) © 2010 Paul Billiet ODWSODWS

7. Growth of the cell is orientated by the appearance of cellulose microfibrils Sap vacuole Plasmodesmata The secondary cell wall consists of cellulose microfibrils secreted inside the primary cell wall When this forms the cell stops growing and takes its final form © 2010 Paul Billiet ODWSODWS