Insulin & Collagen Processing Flashcards
What is the structure of preproinsulin?
Consists of a signal sequence followed by the polypeptide chain split into an a, b and c chain
What happens once preproinsulin has its signal sequence cleaved in the ER?
Proinsulin produced
Disulphides bond formation between a and c chains (molecule bends around)
What happens in the golgi to a molecule of proinsulin?
The carboxyl terminal is trimmed
Removal of the B chain
Insulin produced
Through which type of secretion and through which cells is collagen secreted?
Constitutive secretion
Fibroblasts
What is the most abundant protein in the body?
Collagen
In what type of tissue is collagen abundantly found?
Connective tissue
What is the basic unit of collagen fibres?
Tropocollagen fibres
What is the structure of a tropocollagen molecule?
Right handed triple helix structure formed from 3 polypeptide alpha chains
300nm rod-shaped
Glycine in every 3rd position along each chain
What stabilises the structure of tropocollagen (between the alpha chains)?
Hydrogen bonds
What is the benefit of having glycine as a regularly repeating residue in tropocollagen?
It is small enough to fit in the middle of the helix
What are some physical characteristics of tropocollagen/collagen?
High tensile strength
Non extensible
Non compressible
Which amino acid residues are usually found in the sequence of tropocollagen, apart from glycine?
Mainly proline (hydroxyproline) residues and lysine residues
Where is type 1 collagen typically found in the body?
Skin, tendons, bone, ligaments
What is the structure of type 1 collagen with reference to its alpha chains?
Has 2x alpha-1 chains and 1x alpha-2 chain
Where is type 2 collagen typically found in the body?
Hyaline and elastic cartilage
