Biochemistry of the PDL

Question 1

What do connective tissues consist of

Answer 1

• Cells
• Extracellular matrix which surrounds cells (made of fibres)
• Ground substance

Question 2

What do the cells that make up the connective tissues consist of

Answer 2

• Fibroblasts
• Cementoblasts
• Osteoblasts
• Nerve cells
• Vasculature

Question 3

Describe the minor fibres of the PDL

Answer 3

• Compose 3% of the extracellular matrix
• PDL more closely resembles foetal connective tissues, unlike mature connective tissue
• Some fibres are collagenous, others are elastic

Question 4

Describe the collagenous and elastic fibres in the PDL

Answer 4

• Mature elastic fibres have a microfibrillar component and an elastin core
• The microfibrillar component provides the external tube-like structure
• Most mature connective tissues have elastin fibres in their extracellular matrix

Question 5

Describe the elastin fibres in the extracellular matrix

Answer 5

• Only the microfibrillar part is present, and the
  elastin core forms later after maturation
• The microfibrillar fibres are known as oxytalan fibres (immature elastic fibres)
• As the tissue matures, elastin protein is deposited within the network & the fibres are known as elaunin fibres
• Once the tissue completely matures, classical elastin fibres are revealed

Question 6

Describe the major fibres of the PDL

Answer 6

• Collagen Type 1 is predominant
• All types of collagen are made up of 3 alpha polypeptide chains
• Cross-sectionally, the alpha chains are orientated towards the middle of the helix
• Not all types of collagen form fibres

Question 7

Describe the alpha polypeptide chains

Answer 7

• Each chain has a repeating tripeptide structure of glycine followed by two other amino acids
• Hydroxylation of proline maintains stability by forming hydrogen bonds with surrounding solution and for helix stability

Question 8

Fill the boxes

Answer 8

Question 9

Whats the importance of hydroxyproline and Vitamin C

Answer 9

• Vital for stabilisation of the collagen triple helix through hydrogen bonding of the hydroxyl group
• Proline is converted to hydroxyproline through Prolyl hydroxylase, a vitamin C dependent enzyme

Question 10

Describe type 1 procollagen assembly

Answer 10

• a-chains assemble at the C terminal
• This is stabilised by S-S bonds
• Helix forms spontaneously when in register
• Sugars are added in the RER and golgi

Question 11

Describe the hydroxylation of proline