1. Cell Coverings
Section 4.7

2. Learning Objectives Identify different types of cell coverings
Compare and contrast the extracellular matrix and the cell wall

3. Extracellular Matrix (ECM)
ECM = A network of protein fibers & polysaccharides secreted by the cell
Main structural component is collagen
Connected to the outside of the cell membrane by integrins (a type of receptor protein)
Found in animal cells

4. Function of ECM Protects, supports, & gives shape to the cell
Is porous (full of holes)
Allows water & solutes to cross to the plasma membrane

5. Cell Wall Made of proteins & polysaccharides
Found in plants, fungi, and bacteria
In plants it is made mainly of cellulose
In bacteria it is made mainly of peptidoglycan
In fungi it is made mainly of chitin

6. Function of Cell Wall Cements neighboring cells together
Protection from disease-causing organisms
In plant cells, prevent the cell from exploding due to increased pressure from the central vacuole

7. Cell Wall In Plants Plants secrete two types of cell walls
Primary cell wall
Secondary cell wall

8. Primary Cell Wall Has cellulose in it Is thin & flexible
Allows the cell to grow & change shape

9. Secondary Cell Wall Forms in some types of plant cells
Deposited between the plasma membrane & the primary cell wall
Is a firm & rigid layer
Contains lignin
Makes it stronger, waterproof, & protects against plant-attacking organisms
Wood is made mainly of secondary cell walls

10. Secondary Cell Wall