Connective Tissue or "Introduction to fundamentals of biomedicine" Flashcards
Describe the general features of connective tissue
distributed throughout the body and is used for support (tendon/ligament), intercellular binding (liver/muscle), and as a matrix for deposition of salts (bone and teeth)
Describe the ground substance of connective tissue
Contains proteoglycans which extract water/ions to form a matrix in the extra cellular space
What roles do collagen and elastin play in connective tissue?
They are structural proteins that are secreted into the matrix by connective tissue cells (fibroblasts, chondrocytes, and osteoblasts)
Name three specialised proteins in connective tissue
fibrillin= scaffold for deposition of Elastin Fibronectin = binds interns and other extracellular matrix proteins laminin = basal lamina
What is collagen?
protein that is present in nearly all the tissues - makes up 25-30% of our total body protein. There are more than 20 different types of collagen used in different tissues- but they are classified as fibril collagens, network forming collagens, and fibril associated collagens.
Describe the structure of collagen
- fibrous protein
- triple helical structure
- stabilized by interchain H bonds
- exposed R groups on the triple helical structure allow for interactions with other collagen fibers.
How is Collagen synthesized?
Long story short - gene transcribed, series of post translational changes allow it to fold into a triple helical structure with interchain and intrachain disulfide bonds at the C-terminal propeptide extensions.
How does Collagen cross-link?
Collagen crosslinks when lysyl oxidase deaminates some lysyl and hydroxylysyl residues
The resulting reactive aldehydes (allylysine and hydroxyallylysine) can covalently bond with lysyl or hydroxylysyl
Crosslinking is essential for their tensile strength.
How is collagen degraded?
Degraded via collagenases (matrix metalloproteinases)
then the matrix proteinases further degrade to amino acids
What does pro-collagen peptidase do?
Cleaves N-term and C-term propeptides releasing triple helical collagen molecules
How is vitamin C deficiency related to connective tissue?
Scurvy/Vit. C deficiency
with a deficiency of vit. C the collagen fibers cannot be cross-linked -therefore there is a dereased tensile strength.
This results in bruising, capillary fagility, spongy gums, bleeding from mucous membranes, paleness, lethargy and depression
in advanced cases there could be loss of teeth, open wounds, jaundice and fever
What is Ehlers Danlos Syndrome?
Collagen disorder- defect in metabolism of fibrillar collagen - has mild to serious forms
symptoms: hypermobile joints and skin
What is osteogenesis imperfecta?
aka- brittle bone disease
Collagen disorder: can be a decrease in production (mild form) or altered collagen structure (severe form)
symptoms :bendable bones that fracture easily and slow wound healing - most common symptom is blue sclera of the eyes.
What is Elastin?
Connective tissue fibrous protein with rubber like properties - found in lungs, large artery walls, and ligaments
How is elastin synthesized?
It is synthesized from a tropoelastin precursor that crosslinks via the lysyl oxidase to give elastin
How is elastin degraded?
degraded by elastase - which is secreted by neutrophils
elastase is inhibited by alpha1 antitrypsin - which prevents innapropriate degradation of elastin (particularly in the lungs)
What is Marfan Syndrome?
elastin disorder caused by mutuation in fibrillin gene -
symptoms: range from mild to severe and include tall long limbs, arachnodactyly (spider fingers), impaired structures, defects in heart valves
what is Alpha1 antitrypsin deficiency?
deficiency of the enzyme that prevents elastin degradation. This deficiency therefore leads to innapropriate degradation of elastin by elastase.
symptoms: premature emphysema due to destruction of connective tissue in alveoli
Can be treated with weekly injections of this enzyme
Where is proline and lysin hydroxylated?
proline = on the top of Pentamer
Lysine = third carbon on R group of lysine
What does pro-collagen peptidase do?
cleaves the N and C terminal pro-peptides
How does collagen cross - link?
It cross links via covalent bonding between the lysine/hydrozylysine and the allylys/hydroxyallylys
