Collagen Flashcards
What is the most abundant protein in the body?
Collagen
What is the structure of collagen?
Three alpha chains wind around each other to give a triple helix come together to form microfibrils come together to form fibrils come together to form fibres
Which types of collagen are the “fibrillar” ones?
Types 1-3
What is the role of the fibrillar collagens?
Give strength to tissues
Which types of collagen are the “amorphous” ones?
Types 4-6
What is the most common type of collagen in the body?
Type 1
Where is type 1 collagen found in the body?
Hard tissues - bone
Soft tissues - tendons, ligaments, skin, blood vessels, hollow organs, sclera
Where is type 4 collagen found?
Basement membrane
What secretes type 4 collagen in the basement membrane?
Epithelial cells
How long does collagen synthesis take?
1-2 hours
What enzyme is responsible for collagen remodelling?
Collagenase
Give an example of an acquired disease due to defective collagen synthesis
Scurvy
Give examples of three inherited diseases due to defective collagen synthesis
Ehler’s Danlos syndrome
Osteogenesis imperfecta
Alport syndrome
What is the cause of scurvy?
Vitamin C deficiency
How does vitamin C deficiency affect collagen synthesis?
Reduced hydroxylation of procollagen alpha chains
How does vitamin C deficiency affect the strength of collagen?
Reduced cross-linking between chains, microfibrils, fibrils
weaker collagen
Collagen in ……………………. is particularly affected
Blood vessels
What are the symptoms of scurvy?
Porlonged bleeding
Tooth loss
Old scars becoming fresh wounds
Why does prolonged bleeding occur with scurvy?
Unale to heal wounds
Why does tooth loss occur with scurvy?
Collagen in perodontal ligament has short half-life
replaced by defective collagen
Why do old scars open up as fresh wounds with scurvy?
High collagen turnover in scars for 2 years after their formation
replaced by defective collagen
What is the cause of Ehler’s Danlos syndrome?
Defective conversion of procollagen to tropocollagen
How are collagen fibres different in Ehler’s Danlos syndrome?
Lack tensile strength, are weak
What are the features of skin in Ehler’s Danlos syndrome?
Hyperextensible, recoils
Thin
Fragile
Susceptible to injury
Why is the skin hyperextensible?
Elastin fibres stretch a lot, not held in check by tethering effect of collagen
then recoil
What are the features of joints in Ehler’s Danlos syndrome?
Hypermobile
Predisposed to dislocation
What are the complications of Ehler’s Danlos syndrome?
Rupture of colon
large arteries
cornea
Retinal detachment
What is the cause of osteogenesis imperfecta?
Lack fo type 1 collagen
What are the features of osteogenesis imperfecta?
Fragile bones Deformation of bones - progressive, severe Blue sclera Dental abnormalities Hearing impairment
Why are bones fragile and deformed in osteogenesis imperfecta?
Lack of bone tissue
cannot withstand mechanical stress
break easily, deformed easily
Why is the sclera blue with osteogenesis imperfecta?
Lack of collagen within
so it’s translucent
Which chromosome is faulty in Alport syndrome?
X chromosome
Which gender is more commonly affected by Alport syndrome?
Males
What is the cause of Alport syndrome?
Defective type 4 collagen
How do people with Alport syndrome present?
Haematuria when children
Renal failure as adults
What are the features of Alport syndrome?
Dysfunction of glomerular basement membrane
lens of eye
cochlea of ear
What can the dysfunctional glomerular basement membrane lead to?
Kidney failure
What can the dysfunctional lens of the eye lead to?
Eye disorders
What can the dysfunctional cochlea of the ear lead to?
Neural deafness
