Q: Which repeating sequence is characteristic of the primary structure of collagen?

$$\text{Gly-X-Y}$$, where X and Y are often proline and hydroxyproline

Question 1

Which of the following best describes the primary structural feature that gives collagen its tensile strength?

Accepted Answer

A rope-like triple helix formed by three polypeptide chains stabilized by interchain hydrogen bonds

Question 2

A patient presents with fragile skin, hyperextensible joints, and frequent bruising. Genetic analysis reveals a defect in the gene encoding type III collagen. Which disorder is most likely?

Accepted Answer

Ehlers-Danlos syndrome (vascular type)

Question 3

Which amino acid is found at every third position in the primary structure of collagen, allowing tight packing of the triple helix?

Accepted Answer

Glycine

Question 4

Hydroxylation of proline and lysine residues in collagen requires which vitamin as a cofactor?

Accepted Answer

Vitamin C

Question 5

A deficiency in which enzyme would most directly impair the formation of covalent cross-links between collagen molecules, leading to decreased tensile strength?

Accepted Answer

Lysyl oxidase

Question 6

Which of the following best explains why scurvy leads to weakened blood vessels and poor wound healing?

Accepted Answer

Impaired hydroxylation of proline and lysine residues, resulting in unstable collagen triple helices

Question 7

Which type of collagen is most abundant in cartilage and is essential for its structure?

Accepted Answer

Type II

Question 8

A mutation in the gene encoding fibrillin-1 leads to which of the following connective tissue disorders, characterized by tall stature, lens dislocation, and aortic aneurysms?

Accepted Answer

Marfan syndrome

Question 9

Which of the following best describes the role of lysyl oxidase in collagen and elastin maturation?

Accepted Answer

It oxidatively deaminates lysine and hydroxylysine residues, enabling covalent cross-link formation

Question 10

Which of the following statements about elastin is TRUE?

Accepted Answer

Elastin fibers are composed of elastin and glycoprotein microfibrils such as fibrillin

Question 11

A 5-year-old child presents with multiple bone fractures, blue sclerae, and hearing loss. Genetic testing reveals a mutation in the COL1A1 gene. Which process is most likely disrupted?

Accepted Answer

Assembly of type I collagen triple helix

Question 12

Which of the following best explains the molecular basis for the extensibility and recoil of elastic fibers in tissues such as the lungs and arteries?

Accepted Answer

A cross-linked, amorphous network of elastin molecules

Question 13

Which of the following is a direct consequence of alpha-1 antitrypsin (AAT) deficiency in the lungs?

Accepted Answer

Uncontrolled degradation of elastin by elastase

Question 14

Which repeating sequence is characteristic of the primary structure of collagen?

Accepted Answer

$$	ext{Gly-X-Y}$$, where X and Y are often proline and hydroxyproline

Question 15

During collagen biosynthesis, which step occurs in the extracellular space?

Accepted Answer

Cleavage of N- and C-terminal propeptides from procollagen

Question 16

A patient with a mutation in the gene encoding type IV collagen would most likely have defects in which tissue structure?

Accepted Answer

Basement membranes

Question 17

Which of the following best describes the difference between fibrillar and network-forming collagens?

Accepted Answer

Fibrillar collagens (types I, II, III) form rope-like fibers for tensile strength, while network-forming collagens (types IV, VIII) form 3D meshworks in basement membranes

Question 18

Which post-translational modification is unique to collagen and is essential for its stability?

Accepted Answer

Hydroxylation of proline and lysine residues

Question 19

Which of the following best explains why glycine is critical for the structure of collagen?

Accepted Answer

Glycine's small size allows tight packing of the triple helix

Question 20

A researcher is studying a new connective tissue disorder characterized by impaired cross-linking of elastin. Which enzyme is most likely deficient in this disorder?

Accepted Answer

Lysyl oxidase

Fibrous Proteins: Structure, Function, and Clinical Relevance

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