Biochem & Genetics

Question 1

What are the adhesion proteins in the ECM of bone tissue?

Answer 1

Fibronectin and Laminin

Question 2

What are the fibril-forming collagen types?

Answer 2

Type 1: Skin, bone, tendon, blood vessels, cornea

Type 2: Cartilage, IVD, vitreous body

Type 3: Blood vessels, skin, muscle

Question 3

What are the network-forming collagen types?

Answer 3

Type 4: basement membrane

Type 5: corneal and vascular endothelium

Question 4

What are the fibril-associated collagen types?

Answer 4

Type 9: cartilage

Type 10: tendon, ligaments, other tissues

Question 5

What is the most abundant protein in the body?

Answer 5

Collagen

Question 6

What is the microscopic structure of collagen? What are they stabilized by?

Answer 6

3 helical alpha-helices in a rope formation

Stab by interchain H-bonds

Question 7

How many amino acids does one collagen a-helix contain? What gene encodes these?

Answer 7

~1000 AA

-a1, a2, etc in different combinations creates large # of collagen types

Question 8

What are the most common modifications to a-helices in collagen? What is required to make these modifications?

Answer 8

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

Question 9

Why are alpha-helix collagen fibers modified?

Answer 9

Increase stability (more H-bonds)

Question 10

Why does vitamin C deficiency cause scurvy?

Answer 10

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

Question 11

What enzyme deaminates lysine and hydroxylysine in collagen fibers? What metal is integral in this enzyme? Why have it?

Answer 11

Lysyl oxidase; Copper

-it leads to spontaneous condensation of adjacent side chains, resulting in covalent cross links in collagen increase strength

Question 12

What can copper deficiency lead to?

Answer 12

Menkes syndrome

Question 13

What are some characteristics of elastin?

Answer 13

Rubbery network that can stretch or bend in any direction

Question 14

What enzyme promotes desmosine cross-linking in elastin fibers?

Answer 14

Lysyl oxidase

Question 15

What is the precursor of elastin?

Answer 15

Tropoelastin

Question 16

What are fibrillins? What is their function in elastin?

Answer 16

Family of glycoproteins (fibrilin-1 is major one)

Provide scaffolding of elastin

Question 17

What are laminins? What are their functions?

Answer 17

• 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)

Question 18

What are the characteristics of fibronectin? What are its functions?

Answer 18

• 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

Question 19

What are the differences between proteoglycans and glycoproteins?

Answer 19

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)

Question 20

What are the functions of proteoglycans?

Answer 20

• form gel-like matrix in the body’s ground substance
• Flexible support of ECM
• Movement of materials through ECM
• Viscous, lubricating properties of eCM

Question 21

What are glycosaminoglycans (GAGs)? What are some characteristics?

Answer 21

• Large complexes of - charged heteropolysaccharide chains

- Unbranched, with repeating disaccharide units

Question 22

How many major classes of GAGs are there? What differentiates these classes?

Answer 22

6 different classes based on type of glycosidic links and degree/location of S-S bonds

Question 23

What are the steps and subunits required for GAGs synthesis?

Answer 23

1) Core protien
2) Carbohydrate chains
3) Sulfonation

Question 24

What are the forms of GAG degradation?

Answer 24

Endocytosis and lysosomal (specific acid hydrolases) degradation