Question 1

Which of the following best describes the primary structural feature that allows collagen to form a stable triple helix?

Accepted Answer

The presence of glycine at every third position in the amino acid sequence

Question 2

A patient presents with bleeding gums, poor wound healing, and bruising. Laboratory tests reveal a deficiency in vitamin C. Which step in collagen synthesis is most directly impaired?

Accepted Answer

Hydroxylation of proline and lysine residues

Question 3

Which enzyme is responsible for the oxidative deamination of lysine residues in collagen, and what cofactor does it require?

Accepted Answer

Lysyl oxidase; requires $$Cu^{2+}$$

Question 4

Which type of collagen is the main component of the basement membrane and forms a planar mesh rather than fibrils?

Accepted Answer

Type IV collagen

Question 5

A mutation in the COL4A5 gene leads to Alport syndrome. Which of the following clinical findings is most directly explained by the loss of the size barrier in the glomerular basement membrane?

Accepted Answer

Hematuria

Question 6

Which of the following best explains why elastin is able to stretch and recoil in tissues such as the lungs and arteries?

Accepted Answer

The presence of desmosine cross-links between elastin monomers

Question 7

Which of the following ECM components is primarily responsible for resisting compressive forces in cartilage due to its high negative charge and water retention?

Accepted Answer

Aggrecan (a proteoglycan)

Question 8

Which of the following statements about integrins is TRUE?

Accepted Answer

They mediate bidirectional signaling between the ECM and the cell

Question 9

A patient with Ehlers-Danlos syndrome is found to have a mutation in the COL3A1 gene. Which tissue is most likely to be affected?

Accepted Answer

Blood vessels

Question 10

Which of the following best describes the role of matrix metalloproteinases (MMPs) in tissue remodeling?

Accepted Answer

They degrade ECM proteins such as collagen and gelatin

Question 11

Which of the following is a key difference between inside-out and outside-in integrin signaling?

Accepted Answer

Inside-out signaling is initiated by intracellular signals that activate integrin affinity, while outside-in signaling is triggered by ECM binding to integrins

Question 12

Which of the following cell junctions is primarily responsible for maintaining tissue integrity by linking intermediate filaments between adjacent cells?

Accepted Answer

Desmosomes

Question 13

A patient with pemphigus vulgaris develops oral blisters. This is best explained by autoantibodies targeting which protein?

Accepted Answer

Desmoglein-3

Question 14

Which of the following best explains the function of gap junctions in cardiac muscle?

Accepted Answer

They allow the passage of ions and small molecules for coordinated contraction

Question 15

Which ECM component is most directly involved in the filtration function of the glomerular basement membrane (GBM) in the kidney?

Accepted Answer

Type IV collagen

Question 16

Which of the following best describes the role of fibronectin in the extracellular matrix?

Accepted Answer

It connects cells to the ECM by binding to integrins, collagen, and proteoglycans

Question 17

A patient with Menkes disease has defective collagen cross-linking. Which enzyme is most likely deficient?

Accepted Answer

Lysyl oxidase

Question 18

Which of the following best explains why hyaluronic acid injections are used as a treatment for osteoarthritis?

Accepted Answer

Hyaluronic acid increases the viscosity and elasticity of synovial fluid, improving joint lubrication

Question 19

Which of the following is a direct consequence of excessive ECM deposition in fibrosis?

Accepted Answer

Organ dysfunction due to increased tissue stiffness

Extracellular Matrix and Cell Adhesion: Structure, Function, and Clinical Relevance

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