Biochem of the PDL 1 Flashcards
what’re the cells present in the PDL
fibroblasts
cementoblasts
osteoblasts
what’re the fibres present in the extracellular matrix called
major fibres = collagen
minor fibres = oxytalan elaunin, (elastin in mature fibres)
what type of fibres are elastin fibres found in
mature
what are oxytalan fibres also known as
immature elastin fibres
what type of collagen fibres are present in the PDL
mostly I but also III
what’s the structure of collagen fibres
- 3x polypeptide chains
- triple helix
What’s the primary structure (a.a) of a-chains in type 1 collagen
GLY-X-Y
In the primary structure of a-chains of type 1 collagen what does the X stand for
+ what happens to the characteristics of it
PRO or HYP
- more stability & forming H-bonds
what disease can occur if collagen fibres aren’t hydroxylated
scurvy (absence of vit.C)
what’s tropocollagen
an individual collagen fibre (not connected to another)
-no terminal propeptides
what’re the 2 terminals on procollagen molecules
-C -N
why can’t procollagen form fibres?
due to terminal propeptides at each end
What post-secretory enzyme makes procollagen -> tropocollagen
+how does it do this
procollagen peptidases
- cleave off N- and C- propeptides
- this allows it to form fibres
how is tropocollagen arranged when in fibres (what’s the name of the structure)
1/3 stagger array
what’re the links between tropocollagen molecules called
reducible intermolecular cross links
what does Lysyl oxide do
converts R groups to aldehyde form:
LYS -> allysine (aldehyde form)
HYL -> hydroxyallysine (aldehyde form)
+ Forms reducible intermolecular cross-links
what types of bonds are reducible intermolecular cross links
covalent
reducible intermolecular cross links can be formed between all combinations of ___ and ___ + their _____
+ where they called
LYS & HYL & their aldehyde forms
allysine + LYS = LNL
allysine/LYS + HYL = HLN
HYL + HYL = DHLN
what’s the ratio of DHLN:HLN in the PDL
1:3
are there non-reducible cross links in the PDL & why
no
due to fast cell turnover
what’re the overall steps of Collagen I biosynthesis
(HINTS
1. s______ of _______ in the ____
2. h______ of ______ & _____ with use of ______
3. g________ of ____ & ______
4. _____ bonds forming of the _______
5. Forming a _____
6. Final processing step in the ______ to add more ____
7. secretion
8. Cleave ____ with use of ________
9. ________ formed
10. Formation called the _________
11.intermolecular cross link formed by _____
- synthesis of a-chains in RER
- hydroxylation of PRO & LYS (w. vit.C)
- glycostlation of HYL & allysine
- S-S bonds of pro-a-chains
- procollagen triple helix formed
- more sugars added in Golgi
- secretion
- cleave terminals propeptides (procollagen peptidases)
- tropocollagen formed
- quater stagger array
- cross link formation (lysyl oxidase)
is procollagen intracellular or extracellular
intracellular
is tropocollagen intracellular or extracellular
extracellular
what’re the enzymes called that help degrade collagen
collagenases
What cells form collagen in the PDL
fibroblasts
what 2 ions do collagenases need to work
Ca2+ & Zn2+
what inhibits collagen degradation
TIMP
what’re the biochemical changes in the PDL in case of disease in terms of collagen & gelatinases
collagen content decreases
gelatinise activity increases
what do gelatinises do
further degradations of collagen in the PDL
What enzyme is responsible for the post-translational modification of PRO->HYP
+ what’s the co-factor
+ what’s the reducing agent
Prolyl hydroxylase
+ Fe2+
+ Vit.C
How is procollagen assembled(4)
1. _____ assemble at _ terminal
2. _____ bonds formed which add ______
3. _______ formation
4. _______ added in the ___ & _____
A-chains assemble at C terminal
S-S = stabilised
Spontaneous helix formation
Sugars added in RER & Golgi
How is tropocollagen formed
1.Procollagen
2.procollagen peptidases
3. Cleaves N- & C- propeptides
4.=tropocollagen
How are fibrils stabilised
+ what’re the cross links between
Covalent cross links
LYS HYL
How do non-reducible cross links form
Spontaneously with age
The PDL has non-reducible cross-links (true or false) + why
False
+ rapid turnover rate in collagen
Are collagenases endopeptidases or exopeptideases
+ why
Endopeptidases
+ cleaves collagen fibres in the middle of the chains, not at either end
When collagen degradation takes place, what fragment lengths are they cleaved into?
1/4 +3/4
