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Extra cellular
components
Collagen microfibrils
Image Credit: Fine structure of collagen circa 1948
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 ODWS
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 cellsurface receptors

© 2010 Paul Billiet ODWS
Animal tissues
Image Credit; www.steve.gb.com/
THE PLANT CELL WALL
The formation of
a cell plate starts
as soon as the
nucleus has
divided
© 2010 Paul Billiet ODWS
Cell plate to cell wall
The cell plate
becomes the
middle lamella
that glues the cells
together
© 2010 Paul Billiet ODWS
New cell wall material
is secreted either side
of the middles lamella
= primary cell wall (no
cellulose)
Growth of the cell is orientated by
the appearance of cellulose
microfibrils
Plasmodesmata
Sap vacuole
© 2010 Paul Billiet ODWS
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