Connective Tissue

Question 1

Describe the cellular contact with each other in CT

Answer 1

Cells have few contacts with each other

Question 2

How much ECM is there in CT

Answer 2

Large amount of ECM

Question 3

Where is CT located in relation to epithelium and basal lamina?

Answer 3

CT is under the basal lamina which is under epithelium

Question 4

What is the ECM?

Answer 4

Spaces between cells composed of a complex array of molecules

Question 5

What is the ECM composed of?

Answer 5

Tough fibrous proteins embedded in a polysaccharide gel like material

Question 6

What is the polysaccharide gel like material in the ECM called?

Answer 6

The ground substance

Question 7

How is there a variety of CTs?

Answer 7

Different composition and arrangement of ECM

Question 8

Describe the ECMs in Tendon, Bone and Cartilage CT

Answer 8

Tendon (muscle to bone CT) - numerous fibrous proteins, little ground substance
Bone - calcified ground substance and fibrils
Cartilage - large amount of polysaccharide gel

Question 9

Name some of the roles the ECM plays?

Answer 9

Structural support and regulation of cellular activities

Question 10

How is the ECM produced?

Answer 10

By cells within it, so the cells produce, secrete and organize components of ECM

Question 11

what is one of the most abundant proteins in the ECM?

Answer 11

Collagen and must be correctly aligned and organised

Question 12

Different cells produce ECM depending on the tissue. Name the cells that produce the ECM in the following tissues;

1) Loose connective tissues
2) Bone
3) Cartilage
4) Basement membrane in epithelia

Answer 12

1) Fibroblasts
2) Osteoblasts
3) Chondroblasts
4) Epithelial cells

Question 13

ECM is composed of what two main things?

Answer 13

Proteins and proteoglycans

Question 14

What proteins are in the ECM and examples of them

Answer 14

Fibrous/Structural (Collagen and Elastin)

Adhesive (Laminin)

Question 15

What does collagen provide?

Answer 15

Provides tensile strength

Question 16

What amino acids is Collagen rich in?

Answer 16

Proline and Glycine arranged in repeats as a helical polypeptide chain

Question 17

What is the collagen structure of an alpha chain

Answer 17

Gly-X-Y triplets
X= Proline or Lysine
Y = HydroxyProline or Hydroxylysine

Question 18

What does a collagen molecule consist of?

Answer 18

3 alpha chains into an alpha helix, 1.5nm diameter

Question 19

Alpha collagen chain is what handed and why?

Answer 19

Left handed due to dihedral angle of prolines

Question 20

What are collagen fibrils?

Answer 20

Collagen molecules assembled, outside of the cell, together via covalent cross linking

Question 21

Regular packing of collagen molecules in fibrils leads to what?

Answer 21

Cross stations

Question 22

Collagen fibrils pack together to form what?

Answer 22

Fibres

Question 23

Name the type of collagen formation that doesnt form fibres?

Answer 23

Fibril Associated Collagens

Question 24

Describe the structure of the FAC

Answer 24

Triple helix interrupted by non-helical domains which gives flexibility

Question 25

Is FAC cleaved after secretion?

Answer 25

No, retains propeptides

Question 26

Do FACs aggregate to form fibrils?

Answer 26

No

Question 27

Describing the binding of FACs

Answer 27

Bind periodically to other collagen fibrils. | Type IX binds Type II fibrils. Type XII binds Type I fibrils

Question 28

Name the 8 stages in collagen synthesis?

Answer 28

1) Synthesis of pro alpha chain 2) Hydroxylation of selected prolines and lysines 3) glycosylation of selected hydroxylysines 4) self assembly of 3 pro alpha chains 5) procollagen triple helix formation 6) secretion 7) cleavage of propeptides 8) self assembly into fibril

Question 29

Where does the synthesis of Pro Alpha Chain/ Procollagens take place?

Answer 29

Outside of the ER lumen

Question 30

N and C terminal ends of the pro alpha chain have what?

Answer 30

the propeptide

Question 31

Intrachain disulfide bonds between the N and C terminal propeptide sequences do what?

Answer 31

Align chains to form triple helix in ER

Question 32

Procollagen is modified where and secreted by what?

Answer 32

Modified in ER and Golgi | Secreted by exocytosis

Question 33

Where is the assemblied 3pro-alpha-chain secreted into?

Answer 33

Extracellular space

Question 34

Name the extracellular enzymes and the function of them in relation to the 3pro-alpha-chain

Answer 34

Procollagen peptidases remove N and C terminal propeptides

Question 35

After the removal of propeptides, what occurs?

Answer 35

Self polymerises into fibrils

Question 36

What do the collagen pro-peptides prevent?

Answer 36

Premature assembly of collagen in side cells

Question 37

After secretion, what happens in terms of covalent bonding?

Answer 37

Covalent bonds (lysine resides) cross link the collagen molecules

Question 38

How is tensile strength of collagen determined?

Answer 38

Extent of cross linking. | High cross linking gives high tensile strength which occurs in tendons

Question 39

What are the 3 defects in collagen?

Answer 39

Collagen I - Otsteogensis imperfecta (brittle bones), variety of mutations - failure to form triple helices Collagen II - Achondrogensis - Abnormal bone and joint formation Collagen III - Fragile skin, blood vessels and hypermobile joins, elastic skin

Question 40

What is scurvy caused by?

Answer 40

Failure to hydroxylate prolines and lysines in fribrillar collagen due to reduced levels of ascorbate (vitamin c)