3 - Extracellular Matrix Biology 1

Question 1

What are fibroblasts?

Answer 1

cells that synthesise the ECM and collagen (most commonly found in connective tissue)

Question 2

Define the ECM

Answer 2

a complex network of proteins and carbohydrates that fill the spaces between cells

Question 3

What are the functions of the ECM? (3)

Answer 3

• physical support
• determines mechanical and physiochemical properties of the tissue
• influences the growth, adhesion and differentiation of the cells with which it interacts
• essential for development - tissue function and organogenesis

Question 4

What is connective tissue?

Answer 4

ECM + component cells

it is rich in ECM
macrophages are present

Question 5

What is the function of the basal lamina?

Answer 5

separates the epithelia from the connective tissue

Question 6

From which mutation does Osteogenesis Imperfecta arise?

Answer 6

Type I collagen

Question 7

From which mutation does Marfan’s syndrome arise?

Answer 7

Fibrillin 1

Question 8

From which mutation does Alport’s syndrome arise?

Answer 8

Type IV collagen

Question 9

From which mutation does Epidermolysis Bullosa arise?

Answer 9

Laminin 5

Question 10

From which mutation does congenital muscular dystrophy arise?

Answer 10

Laminin 2

Question 11

What are the properties of the connective tissue in the tendons and skin?

Answer 11

tough and flexible

Question 12

What are the properties of the connective tissue in the vitreous humous?

Answer 12

soft and transparent

Question 13

What are the properties of the connective tissue in bone?

Answer 13

hard and dense

Question 14

What are the properties of the connective tissue in cartilage?
(found in joints - softer and more flexible than bone)

Answer 14

resilient and shock absorbing

Question 15

Which cells make the ECM components?

Answer 15

fibroblasts

Question 16

What is the arrangement of collagen in the tendons? What significance does this have?

Answer 16

layers of collagen fibrils are laid down almost parallel to one another - this give the tissue tensile strength (ability to resist stress) in 2 directions

Question 17

What constitutes the triple helix in collagen?

Answer 17

can be comprised of one or more different types of alpha chains

• type 1 collagen - 2 α1 chains and 1 α2 chain
• types 2 and 3 collagen (only have one chain type) - 3 α1 chains

Question 18

What constitutes the triple helix in collagen?

Answer 18

comprised of one or more different types of alpha chains

• type 1 collagen - 2 α1 chains and 1 α2 chain
• types 2 and 3 collagen (only have one chain type) - 3 α1 chains

Question 19

How do the individual helices form collagen?

Answer 19

• individual triple helices come together to form fibrils

- fibrils come together to form collagen fibres

Question 20

Give the order of events in collagen biosynthesis

Answer 20

• synthesis of pro-α chain
• hydroxylation of prolines and lysines
• glycosylation of hydroxylysines
• self assembly of 3 pro-α chains
• procollagen triple helix formation
• secretion
• cleavage of propeptides
• self assembly into fibrils
• aggregation pf collagen to form a colagen fibre

Question 21

What enzymes hydroxylate the residues on the pro-α chains?

What do they require to function?

Answer 21

proplyl and lysyl hydroxylases,

require vitamin C and iron to function

Question 22

What does a deficiency of vitamin C cause?

Answer 22

scurvy:
there is a lack of proper collagen hydroxylation, so they can’t aggregate together properly and form firm collagen fibres which affects the tissue stability

Question 23

How are elastic and collagen related?

Answer 23

they are often interwoven to limit the extent of stretching

Question 24

Where can elastin be found in the body?

Answer 24

skin, blood vessels and lungs

Question 25

What is the basement membrane?

Answer 25

• flexible, thin mats of ECM that surrounds muscle, peripheral nerves, fat cells and underlie most epithelia
• in the kidney glomerulus, it prevents macromolecules from going form the blood into the nephron
  NOTE: diabetic nephropathy - ECM accumulation - restricts renal filtration and causes renal failure