ECM

Question 1

Why is the ECM important

Answer 1

Because solid tissues can only be made if the cells interact in specific ways with other cells or the ECM

This interaction with the ECM can influence the behaviour of the cells

Question 2

What is the glycocalyx/cell coat

Where are they most prominent

Answer 2

They are carbohydrate projections that are attached to and extend from integral membrane protiens in the cells membrane

It’s the first layer right outside the cell

Epithelial cells

Question 3

What are the roles of the glycocalyx

Answer 3

Mediate cell cell and cell substratum (ECM) interactions

Give mechanical protection to the cells

Serve as a barrier

Question 4

What is the ECM

What can it also be called

Answer 4

It’s made of secreted protiens and is also called the basement membrane

The part after the glycocalyx

Question 5

What is the ECM found in

Answer 5

In epithelial tissues

Surrounds muscle and fat cells,

lines the digestive/respiratory tracts

and the inner endothelial lining of blood vessels

Question 6

What is special about the ECM of cartilage cells

Answer 6

The cartilage cells are called chondrocytes

The chondrocyte has a thick ECM which makes it so that red blood cells and other matter can’t get close to the cell

The ECM acts as a barrier and attracts water only to make a cushion

Question 7

Explain the model of integrin activation

Answer 7

Integrin come in aplha beta pairs

When Inactive, the integrin is bent (not fully extended) and the alpha beta are close together

To become active, a talin from the actin cytoskeleton binds to the beta subunit and induces separation and extension of the two subunits

Question 8

What is an example of outside in activation of integrin

What about inside out

Answer 8

Outside in would be if collagen from outside the cell activated the integrin

Talin from the actin cytoskeleton on the inside activates the integrin

Question 9

What is outside in activation of integrin

Answer 9

The Ligand on the outside of the cell binds to the intgrin in the cell membrane and send a signal to Focal adhesion kinase

This FAK starts a signalling cascade to the nucleus of the cell

Question 10

What is inside out activation of integrin

What increases the strength of the integrins

Answer 10

Occurs from something inside the cell affecting the integrins

The space between the dimers and clustering of the activated integrins enhances the strength of the interaction between the cells surface and the extracellular ligands

Question 11

How do integrins actually make contact with other protiens in the ECM

Answer 11

They have an RGD binding site for the protien in the ECM to bind to.

If the aa sequence of the protien in the ECM has RGD, it binds to the integrin

Arg-gly-asp

Question 12

Do all integrins have RGD binding sites

Answer 12

No

Around 1/2 do

Question 13

What critical signals does the ECM (basement membrane) of epithelial cells provide

Answer 13

Survival

Orientation

Differentiation

Question 14

Breast cancer and epithelial cells ECM experiment

Answer 14

Shows that cancer cells don’t have junction molecules or adhering molecules

So they don’t group together or bind to the ECM

Question 15

What are the four ECM protiens

Answer 15

Collagen (rope)

Proteoglycan (feather)

Fibronectin (dimer)

Laminins (laminins)

All have RGD peptide

Question 16

What is the structure of collagen 1

Answer 16

It’s a triple helix of 3 alpha helices

Fibrous and Only in ECM

Strong

Question 17

What is collagen 1 made by

Answer 17

Made by fibroblasts

that are in the connective tissues, in the dermis below the basement membrane (ECM)

by smooth muscle cells

By epithelial cells

Question 18

In what way does collages stack up and form and why

Answer 18

In antiparallel stacks (some stacks vertical some horizontal, 90 degrees)

This give a insoluble frame work and helps with the clarity and tissue transparency

Question 19

What is an example of how collagens help in the eyes

Answer 19

In the cornea the anitparallel layers give strength and transparency to see through

Question 20

What are proteoglycans function

Answer 20

They bind cations, and those cations bind water molecules to make a porous hydrated gel

This gel gives cushion for joints and resistance to compression

Question 21

How to collagen and proteoglycans work to make better tissues

Answer 21

Collagens resist pulling forces

they form scaffolds with proteoglycans to give strength and resistance

Question 22

What is the structure of proteoglycans

Answer 22

Have a core protien hyaluronate

A bunch of negative charged glycosaminoglycans (saccharides) are attached to this protien

Question 23

What is fibronectin

Answer 23

Dimer

Made of two similar polypeptides (protiens) joined together by two disulphide bonds

Each protiens in this dimer is made of specific modules that bind to ECM components and cell surface receptors (like integrins)

Question 24

What is special about the RDG loop of fibronectin

Answer 24

It is the binding signal to bind to integrins

It has a loop the sticks up so the integrins can bind easier to it

Question 25

Explain the firbronections cells experiment

Answer 25

A plate had a coating of firbronections and cells were put onto it

Using their integrins, the cells attached and moved along the finbtonection

If the leave the fibronectin, they die because the have nothing to adhere to

Question 26

What are laminins structure

Answer 26

Trimers in a cross shape

Glycoprotiens made of three DIFFERENT proteins linked by disulphide binds

Question 27

What are laminins function

What do they bind to

Answer 27

Help with migrations, growth, differentiations, strengthen BM and help in neuronal outgrowth

Bind to cells surface receptors, other laminins, proteoglycans or other BM protiens

They also bind to collagen to make interconnected networks

Question 28

Give an example of how Laminins work

Answer 28

The laminins are use to form the embryo

The germ cells move toward the gonad on basically laminin highways across the embryo