Unit 1: Extracellular Matrix (Lectures 1-2) Flashcards
What is the extracellular matrix ?
A network of secreted macromolecules which maintain cell tissue integrity
What can the ECM influence ? (3)
- Cell shape
- Cell migration
- Cellular function and behaviour
Describe the relationship between matrix and cell
A reciprocal relationship
What are the 2 main types of ECM component ?
1) Glycosaminoglycans
2) Fibrous proteins
What type of molecule is glycosaminoglycan ?
A polysaccharide that is usually covalently linked to a protein
Give an example of a fibrous protein
Collagen
What is the structure of collagens (4) ?
- Covalently cross linked
- Long and inflexible
- Triple helix forming
- 3 alpha chain polypeptides
What is the most common collagen fibre amino acid sequence ?
Glycine-Proline-Hydroxyproline
What are amino acid residues commonly arranged as ?
Triplets
What are the 3 types of collagens ?
- Fibrillar
- Networking
- Fibril associated
What is the function of fibronectin and what is it ?
It is a glycoprotein that functions as a dimer that binds integrin receptors
What are the components of a proteoglycan ?
- Protein core
- GAG side chains
(GAGs are covalently linked to proteins)
What is the structure of a glycosaminoglycan (4) ?
- Un branched
- Composed of repeated disaccharides
- Highly negatively charged so hydrophilic
- Resist compressive forces
What compound allows proteoglycans to produce 3D structures ?
Hyaluronan (Ionic linkage between protein core of PG and hyaluronan)
What is hyaluronan made from ?
- Hyaluronic acid
- Hyaluronate
How does the molecular weight of hyaluronan link to its function ?
- Low molecular weight increases proliferation
- High molecular weight decreases proliferation
What is the role of a proteoglycan ?
They regulate the activity of signalling molecules and can act as co receptors
What is the basal lamina ?
A specific form of extracellular matrix which is found at sites where tissues have a junction with connective tissues
What is the structure of the basal lamina ?
- Continuous flexible mats of specialised ECM
- Very widespread so underlie all epithelia
- Synthesised by cells for which it forms a base
What are 3 functions of the basal lamina ?
- Separates different cell layers providing a barrier to migration
- Acts as a scaffold for regenerating cells after injury and provides signals for reconstruction
- Acts as a selective molecular filter
What are the 2 broad categories of cell junction ?
1) cell-cell junctions
2) cell-matrix junctions
What are the 3 classes of cell junction ?
1) Tight or occluding junctions
2) Anchoring junctions
3) Gap junctions
What is the function of a tight junction ?
Seals cells into a sheet and prevents leakage of molecules across the sheet
What are the 2 surfaces involved in a tight junction ?
- Atypical surface (Top)
- Basolateral surface (Bottom)
