Biochem & Genetics Flashcards
What are the adhesion proteins in the ECM of bone tissue?
Fibronectin and Laminin
What are the fibril-forming collagen types?
Type 1: Skin, bone, tendon, blood vessels, cornea
Type 2: Cartilage, IVD, vitreous body
Type 3: Blood vessels, skin, muscle
What are the network-forming collagen types?
Type 4: basement membrane
Type 5: corneal and vascular endothelium
What are the fibril-associated collagen types?
Type 9: cartilage
Type 10: tendon, ligaments, other tissues
What is the most abundant protein in the body?
Collagen
What is the microscopic structure of collagen? What are they stabilized by?
3 helical alpha-helices in a rope formation
Stab by interchain H-bonds
How many amino acids does one collagen a-helix contain? What gene encodes these?
~1000 AA
-a1, a2, etc in different combinations creates large # of collagen types
What are the most common modifications to a-helices in collagen? What is required to make these modifications?
Hydroxylation of proline and lysine (maybe some glucose/galactose added on lysine as well)
-Oxygen, iron, and Vitamin C are required for these post-translational modifications
Why are alpha-helix collagen fibers modified?
Increase stability (more H-bonds)
Why does vitamin C deficiency cause scurvy?
a-helix in collagen cannot form H-bonds as well, decreased tensile strength and clinical impact from this:
Bruising, loose teeth, poor wound healing, poor bone development
What enzyme deaminates lysine and hydroxylysine in collagen fibers? What metal is integral in this enzyme? Why have it?
Lysyl oxidase; Copper
-it leads to spontaneous condensation of adjacent side chains, resulting in covalent cross links in collagen increase strength
What can copper deficiency lead to?
Menkes syndrome
What are some characteristics of elastin?
Rubbery network that can stretch or bend in any direction
What enzyme promotes desmosine cross-linking in elastin fibers?
Lysyl oxidase
What is the precursor of elastin?
Tropoelastin
What are fibrillins? What is their function in elastin?
Family of glycoproteins (fibrilin-1 is major one)
Provide scaffolding of elastin
What are laminins? What are their functions?
- Cross-shaped glycoprotein with three polypeptides (heterotrimers) encoded by diff genes (15 types of laminins)
- Holds together basement membrane, mediates interactions with overlying cells, and helps trigger physio responses (growth, movement)
What are the characteristics of fibronectin? What are its functions?
- most abundant multi-adhesive in CT; large protein formed from 2 similar polypeptide chains linked by S-S bonds
- Glues cells to fibrous meshwork of ECM; necessary for proper movement of cells; has a role in metastasis of cancer
What are the differences between proteoglycans and glycoproteins?
Proteoglycans: large amm of heteropolysaccharide chains, small amm of protein (95% carbohydrate)
Glycoproteins: protein with a variable (but small) amount of carbohydrates (2-10 sugar residues)
What are the functions of proteoglycans?
- form gel-like matrix in the body’s ground substance
- Flexible support of ECM
- Movement of materials through ECM
- Viscous, lubricating properties of eCM
What are glycosaminoglycans (GAGs)? What are some characteristics?
- Large complexes of - charged heteropolysaccharide chains
- Unbranched, with repeating disaccharide units
How many major classes of GAGs are there? What differentiates these classes?
6 different classes based on type of glycosidic links and degree/location of S-S bonds
What are the steps and subunits required for GAGs synthesis?
1) Core protien
2) Carbohydrate chains
3) Sulfonation
What are the forms of GAG degradation?
Endocytosis and lysosomal (specific acid hydrolases) degradation
