L21- Extracellular Matrix and Connective Tissues Flashcards Preview

From Molecules to Cells BIOL10232 > L21- Extracellular Matrix and Connective Tissues > Flashcards

Flashcards in L21- Extracellular Matrix and Connective Tissues Deck (22)
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1
Q

Why is cellulose so strong?

A

It’s interwoven with other polysaccharides and cross-linked.

2
Q

How do cellulose fibres resist stretching and determine the axis of cell growth?

A

Their orientation determines direction. Like a pipe.

3
Q

How do microtubules affect cellulose?

A

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.

4
Q

Where are cellulose fibrils synthesised?

A

Outside the cell

5
Q

What determines the orientation of cellulose fibrils outside the cell?

A

MTs inside the cell

6
Q

What is cellulose synthase?

A

A cell membrane protein made at the ER, transported via the Golgi to the PM.

7
Q

Give 4 types of connective tissue and where they are found?

A
  1. tough and flexible (skin and tendon)
  2. Hard and dense (bone)
  3. shock-absorbing (cartilage)
  4. Soft and transparent (in eye)
8
Q

What’s the key component of connective tissue?

A

Collagen

9
Q

What makes collagen?

A

Fibroblasts- in the skin and tendon

Osteoblasts- in bone

10
Q

How is collagen synthesised?

A

A precursor- procollagen is secreted. Procollagen cannot assemble into fibrils until it’s cleaved by a protease, outside the cell.

11
Q

Where must procollagen be cleaved?

A

Outside the cell by protease. So that a big chunk of collagen fibril doesn’t form inside the cell.

12
Q

Where does trimerisation of pro-collagen occur and what does it need?

A

In the ER and needs ascorbic acid (vit C).

13
Q

WHy do people get scurvy?

A

Collagen can’t form properly because they lack vit C.

14
Q

What’s the structure of collagen?

A

Procollagen-> triple strand-> collagen fibril -> collagen fibre

15
Q

How are cells linked to the ECM?

A

Integrins:
Trans-membrane proteins in the PM
Link ECM to cell’s cytoskeleton

16
Q

What type of cytoskeleton linkage do

a. migration or collagen-secreting cells have?
b. epithelia monolayers?

A

a. focal adhesions

b. hemi-desmosomes

17
Q

How do cells bind to collagen?

A

They need a linker protein-fibronectin

which is secreted by the cell

18
Q

What joins the cell to collagen?

A

Fibronectin

19
Q

How do motile cells adhere to the ECM or substrate?

A

Focal adhesions, containing integrins

20
Q

When cells are dividing what happens to their grip on the ECM?

A

It weakens because integrins ar phosphorylated

21
Q

What’s in the spaces between fibres?

A

Gels called proteoglycans

22
Q

Give 4 features of proteoglycans?

A
  1. Extracellular proteins (secreted)
  2. Covalently linked to negatively-charged polysaccharides
  3. Strongly hydrophilic
  4. Occupy a huge volume relative to their mass (bind to lots of H20)