Extracellular matrix Flashcards
What is the definition of an extracellular matrix?
Any substance produced by cells and secreted into the extracellular space within the tissues.
Why is the the ECM important?
It provides physical support for the cells and a linkage between different cells or tissues and also forms a substrate on which cells can move and it provides cues that guide the direction of movement.
What are connective tissues made up of?
It is mostly made up of ECM and consists of scattered cells such as fibroblasts.
What is the ECM in connective tissue made up of?
Collage fibre cross-linked by accessory proteins in a matrix of proteogylcans, which is protein and polysaccharides.
What is the structure of epithelial tissues?
It consists of scant ECM that is made up of layers of cells closely bound to one another to form protective sheets. The ECM is concentrated under epithelia to provide a base for the cells to sit on and acts as a molecular sieve and substrate for migrating cells.
What is the ECM in plants made up of?
Cellulose fibres that are cross-linked with hemicellulose in a matrix of highly branched polysarccharides, such as pectin.
What is the other name for the ECM in plants?
The cell wall.
How does plant ECM differ from animal ECM?
Animal ECM is made up of fibres from protein, such as collagen and elastin.
What percentage of the protein mass does collagen make up?
25%.
How many different collagen genes are there in mammals?
42.
How are collagen fibres formed?
Single strands of collagen form a triple stranded collagen molecule that is twisted together. Lots of these triple stranded collagen molecules form collagen fibrils, which then congregate to form collagen fibres.
What is type I collagen?
It forms long fibres.
What is type II collagen?
Networks are more mesh-like.
What is type VI collagen?
Bind collagen fibrils together to form thicker fibres.
What is type XI and V collagen involved in?
They co-assemble into fibres with type I collagen and regulate the structures and properties of the fibres.
What are the cross links between the components of tropocollagen?
Covalent cross links.
What are the cross links between fibrils and fibres?
Hydroxyproline cross-links.
What is the amino acid repeat in collagen molecules?
GlycineXY where X and Y can be any amino acids, but are predominantly lysine, proline, hydroxylysine and hydroxyproline.
What amino acids are the basis of cross-linking between the collagen molecules?
The hydroxified amino acids.
How can collagen be kept in solution and prevent fibres and fibrils being formed?
THere is end that is now glyXY repeat (not triple helical).
What is the importance of these collagen structures that do not form fibrils or fibres?
They are bundled up into secretory vesicles that are taken to the edge of the cell and fused with the plasma membrane and procollagen helices.
What is the function of elastin?
It provides elasticity to tissues.
What is elastin composed of?
Large filaments with lots of random coils that can be compared to springs. It is connected by cross-linked lysine or hydroxylysines.
What happens when elastin stretches?
It flattens out, compared to its relaxed coiled state.
