ECM, Collagen Synthesis, & Disorders

Question 1

Which one of hte following statements about the extracellular matrix (ECM) protein such as collagen is correct?
A. Both the synthesis and processing of ECM proteins takes place exclusively extra-cellularly
B. Both the synthesis and processing of ECM proteins takes place exclusively intra-cellularly
C. The synthesis of ECM proteins takes place extra-cellularly but their processing takes place partly intra-cellularly and partly extra-cellularly
D. The synthesis of ECM proteins takes place intra-cellularly but their processing takes place exclusively extra-cellularly
E. The synthesis of ECM proteins takes place intra-cellularly but their processing takes place partly intra-cellularly and partly extra-cellularly

Answer 1

E. The synthesis of ECM proteins takes place intra-cellularly but their processing takes place partly intra-cellularly and partly extra-cellularly

Question 2

Which one of the following is a transmembrane protein that links the cytoskeleton with the extracellular matrix?
A. Connexin 26
B. Fibrallin-1
C. Integrin
D. Lamin A
E. L1 cell adhesion molecule (L1-CAM)

Answer 2

C. Integrin

Question 3

Collagen is assembled in the cytoplasm and…
A. extracellularly
B. in the endoplasmic reticulum
C. in the golgi apparatus
D. in the mitochondria
E. in the nucleus

Answer 3

A. extracellularly

Question 4

What indicates the nomenclature for Type I collagen, the most abundant type of collagen found in skin, bone, and tendon?

Answer 4

[α1(I)₂α2(I)] designates Type I
collagen which consists of 2 molecules of
Type I α1 chain and 1 molecule of Type II α2
chain.

Question 5

The exons of Col1A1 and Col1A2 typically include codons for what three-unit peptide product that stabilizes collagen in its tertiary structure?
A. Gly-(4-Hyp)-Ile
B. Gly-Gru-Pao
C. Gly-Pro-(4-Hyp)
D. Lys-Gly-(4-Hyp)
E. Pro-Trp-Gly

Answer 5

C. Gly-Pro-(4-Hyp)

Question 6

Which one of the following proteins does not associate with DNA?
A. Collagens
B. Condensins
C. Histones
D. Lamin-associated proteins
E. RNA polymerases

Answer 6

A. Collagens

Question 7

Which one of the following pairs of amino acids are the most abundant in collagen?
A. Cytosine and glycine
B. Glycine and proline
C. Leucine and alanine
D. Lysine and proline
E. Lysine and serine

Answer 7

B. Glycine and proline

Question 8

Which of the following statements is true for collagen?
A. Biologic function determines the arrangement of collagen fibrils
B. Collagen fibrils are formed by the self-assembly of procollagen molecules
C. Glycine makes up nearly one third of the amino acid residues
D. The carbohydrate residues are bound to hydroxyproline
E. The fundamental collagen polypeptide is an alpha-chain that forms alpha-helices

Answer 8

C. Glycine makes up nearly one third of the amino acid residues

Question 9

Which of hte following statements is true for post-translational modification of proteins?

Hydroxylysine is formed by spontaneous oxidation of lysine

Answer 9

TRUE

Question 10

True of False?

Hydroxylation occurs on the collagen protein after synthesis on the ribosome.

Answer 10

True

Question 11

The three individual polypeptide herlices of collagen are tightly wound about each other in a super helix. This winding requires…
A. hydroxylated lysines
B. hydroxylated prolines
C. oxidized lysines
D. periodicity in the positions of glycine

Answer 11

A. hydroxylated lysines

copper is cofactor

Question 12

Ascorbic acid (vitamin C) , needed for the synthesis of functional collagen, is required for reactions catalyzed by:
A. lysine hydroxylase only
B. lysine hydroxylase and proline hydroxylase
C. lysine oxidase only
D. lysine oxidase and proline oxidase
E. proline hydroxylase only
F. proline oxidase only

Answer 12

B. lysine hydroxylase and proline hydroxylase

Question 13

Osteogenesis Imperfecta is an inherited disorder in which there is a mutation in the gene(s) coding for the precursors of:
A. elastic fibers
B. reticular fibers
C. Type I collagen
D. Type III collagen
E. Type IX collagen

Answer 13

C. Type I collagen

Question 14

Clinical features of osteogenesis imperfecta Type III include all of hte following except:
A. Deformity of the chest wall
B. Scoliosis
C. Severe deformities of long bones
D. Short stature due to growth retardation
E. Yellow sclera

Answer 14

E. Yellow sclera

Question 15

Order of post-transcriptional events in collagen synthesis:
1. Protein translation on the rough ER and extrusion into the ER lumen
2. Hydroxylation of proline and lysine residues
3. Addition of glucosyl- and galactosyl-glucosyl moieties
4. Formation of disulfide bonds at cysteine residues in the globular region
5. Triple helix formaiton
6. Secretion into the ECM
7. Cleavage of the globular domains of procollagen
8. Self-assembly into fibrils
9. Intermolecular cross-linking of collagen fibrils at the lysine residues

Answer 15

Correct

Question 16

newborn infant with…
* respiratory distress
* multiple fractures dating back to prenatal period
* blue sclera
* no family hx of fractures

A. EDS type I
B. EDS type III
C. Osteogenesis type I
D. Osteogenesis type II
E. Stickler syndrome

Answer 16

D. Osteogenesis type II

OI type I is the mildest and most common type. Manifestations are bone fragility, with most fractures caused by mild trauma occurring before puberty. The sclerae are blue or have a purple or grayish tint.
OI type II is the most severe form and is
often lethal in the perinatal period because
of respiratory problems. Numerous
fractures sustained prenatally, resulting in
significant skeletal deformity, contribute to
this high mortality. Fractures are also
sustained during birth. The sclerae are blue
or have a purple or grayish tint

Question 17

Ehlers Danlos Syndrome Type IV (vascular type)
A. type I collagen
B. type II collagen
C. type III collagen
D. elastin
E. fibrin

Answer 17

C. type III collagen

Question 18

Which one of the following phenomena is the least likely in cell migration?
A. Active mitosis to replace cells that get lost or died during migration
B. Adhesion to the extracellular matrix
C. Alteration of migrant cell shape
D. Proteolysis induced by protease secreated by the migrating cells secreted to clear the path for migration
E. Secretion of survival factors by non-malignant cells in the matrix through which migration is taking place

Answer 18

A. Active mitosis to replace cells that get lost or died during migration

Question 19

Important factors in successful neural crest migration invovles all of hte following except:
A. chemotactic factors
B. positional identity of the migrating cell based on Hox gene expression
C. receptors for survival factors on the surface of the migrating cells
D. survival factors secreted by non-migrating cells along the way
E. the constitution of the ECM

Answer 19

B. positional identity of the migrating cell based on Hox gene expression

Question 20

Stickler syndrome

Answer 20

• Type II collagen: cartilage, intervertebral disks, vitreous of the eyes
• skeletal dysplasia
• retinal detachment