Biochem: Matrix Proteins

Question 1

Type of collagen found in blood vessels and fetal skin.

Answer 1

Type III

Question 2

Type of collagen found in skin, bone, tendon, blood vessels, cornea

Answer 2

Type I

Question 3

Type of collagen found in basement membranes.

Answer 3

Type IV

Question 4

Type of collagen found in cartilage, IV disc, and virtreous body

Answer 4

Type II

Question 5

Role of Vitamin C in collagen synthesis.

Answer 5

Co-factor for hydroxylation of proline and lysine residues

-the OH functional groups allow hydrogen bonding between helices of collagen units to make the structure stronger

Question 6

Pathogenesis of Menkes Syndrome

Answer 6

X-linked recessive mutation in Copper-Binding ATPase

• prevents adequate uptake of copper from the diet
• copper is needed for the enzyme lysine oxidase, without it tropocollagen units do not cross-link well and the patient usually dies in infancy

Question 7

Pathogenesis of Osteogenesis Imperfecta.

Answer 7

Autosomal dominant mutation in genes required for Type 1 collagen production. Type 1 collagen is either absent or in reduced amounts. Characteristic blue sclera (blue color comes from blood in the choroid veins, the sclera is thinner in this disease making the color more visible)

Question 8

Mildest form and most severe form of Osteogenesis Imperfecta.

Answer 8

Mildest: Type 1

Most severe: Type 2

Question 9

Pathogenesis of the most common type of Ehlers Danlos Syndrome.

Answer 9

Type 3

• mutation in the gene encoding Tenascin-X
• results in Hypermobile Joints

Question 10

Pathogenesis of Type 1 and 2 Ehlers Danlos

Answer 10

Abnormal Type V collagen formation

Question 11

Pathogenesis of Type 4 Ehlers Danlos

Answer 11

Mutation in genes encoding Type III collagen

-vascular condition with a high risk of blood vessel rupture

Question 12

Pathogenesis of Dystrophic Epidermolysis Bullosa (DEB).

Answer 12

Mutation in the gene that encodes Type VII collagen resulting in blisters and breaks in the skin

Question 13

Pathogenesis of Alport Syndrome.

Answer 13

Gene mutation in Type IV collagen production
-leads to abnormal formation of basement membranes
(multiple genes can mutate and result in this condition)

Question 14

Major complication of Alport Syndrome

Answer 14

Renal Failure in early adult life

Question 15

Component of elastin connective tissue that gives it strength.

Answer 15

Cross-linking of lysine residues in elastin chains forming structures called Desmosines

Question 16

Major complication and pathogenesis of William Syndrome.

Answer 16

Supravalvular Aortic Stenosis

• deletion of multiple genes on Chromosome 7
• results in a deficiency of elastin causing unstable blood vessels
• other sequelae include: elfin facial appearance, very trusting personality

Question 17

Complication of Alpha-1 Antitrypsin deficiency.

Answer 17

Emphysema

• the enzyme is needed to inactivate elastases
• without A-1A, elastases are overactive and degrade elastin in alveolar tissue

Question 18

Main connective tissue function of Fibrillin

Answer 18

Polymerizes to form scaffolding for elastin deposition

Question 19

Gene mutated in Marfan Syndrome

Answer 19

Fibrillin-1 gene

Question 20

Main function of Fibronectin.

Answer 20

Component of the extracellular matrix that “glues” cells together

Question 21

Obstetric application for Fibronectin

Answer 21

Fetal Fibronectin Test

• fibronectin is used to hold the amniotic sac to the uterus in pregnancy
• if fetal fibronectin levels are raised from a cervical swab, it could indicate higher risk of preterm labor

Question 22

Pathogenesis of Junctional Epidermolysis Bullosa.

Answer 22

Defect in laminin in skin

• results in instability of the dermoepidermal junction
• blistering of skin and mucous membranes

Question 23

Pathogenesis of Congenital Muscular Dystrophy.

Answer 23

Defect in laminin in muslces

• results in instability of the muscle cell cytoskeleton-extracellular matrix link
• muscle weakness

Question 24

Most abundant Glycosaminoglycan (GAG)

Answer 24

Chondroitin Sulphate

-present in cartilage, tendon, bone, ligaments, cornea

Question 25

GAG that plays a role in corneal transparency

Answer 25

Keratan Sulphate I

Question 26

GAG involved in anticoagulation

Answer 26

Heparin

Question 27

GAG involved in synovial fluid of joints and vitreous humor

Answer 27

Hyaluronic Acid

Question 28

General Pathogenesis of Mucopolysaccharidoses

Answer 28

Deficiency in lysosomal enzymes that degrade GAGs

Question 29

Mucopolysaccharidosis that involves corneal clouding, stiff joints, Aortic Valve disease, normal intelligence, and normal lifespan

Answer 29

Scheie Syndrome

Question 30

Mucopolysaccharidosis that involves mental retardation, corneal clouding, dwarfing, and early death due to depositions in coronary arteries

Answer 30

Hurler Syndrome

Question 31

Mucopolysacharidosis that involves mental retardation, physical deformity, no corneal clouding

Answer 31

Hunter Syndrome