L21- Extracellular Matrix and Connective Tissues Flashcards
Why is cellulose so strong?
It’s interwoven with other polysaccharides and cross-linked.
How do cellulose fibres resist stretching and determine the axis of cell growth?
Their orientation determines direction. Like a pipe.
How do microtubules affect cellulose?
The cellulose fibres aare constrained the way the complexes move. They move parallel to the MT fibres. Cellulose is made by cellulose synthase complexes. Cellulose fibres run parallel to microtubules in the cell.
Where are cellulose fibrils synthesised?
Outside the cell
What determines the orientation of cellulose fibrils outside the cell?
MTs inside the cell
What is cellulose synthase?
A cell membrane protein made at the ER, transported via the Golgi to the PM.
Give 4 types of connective tissue and where they are found?
- tough and flexible (skin and tendon)
- Hard and dense (bone)
- shock-absorbing (cartilage)
- Soft and transparent (in eye)
What’s the key component of connective tissue?
Collagen
What makes collagen?
Fibroblasts- in the skin and tendon
Osteoblasts- in bone
How is collagen synthesised?
A precursor- procollagen is secreted. Procollagen cannot assemble into fibrils until it’s cleaved by a protease, outside the cell.
Where must procollagen be cleaved?
Outside the cell by protease. So that a big chunk of collagen fibril doesn’t form inside the cell.
Where does trimerisation of pro-collagen occur and what does it need?
In the ER and needs ascorbic acid (vit C).
WHy do people get scurvy?
Collagen can’t form properly because they lack vit C.
What’s the structure of collagen?
Procollagen-> triple strand-> collagen fibril -> collagen fibre
How are cells linked to the ECM?
Integrins:
Trans-membrane proteins in the PM
Link ECM to cell’s cytoskeleton
