Q: Which of the following equations correctly represents the reaction catalyzed by prolyl hydroxylase during collagen synthesis?

$$\text{Prolyl residue} + \alpha\text{-ketoglutarate} + O_2$ + \text{Fe}^{2+} + \text{Ascorbate} \rightarrow \text{Hydroxyprolyl residue} + \text{Succinate} + CO_2$

Question 1

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

Accepted Answer

The Gly-X-Y repeating sequence, where X is often proline and Y is often hydroxyproline

Question 2

A patient presents with bleeding gums, poor wound healing, and loose teeth. 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 by prolyl and lysyl hydroxylase

Question 3

Which of the following equations correctly represents the reaction catalyzed by prolyl hydroxylase during collagen synthesis?

Accepted Answer

$$	ext{Prolyl residue} + \alpha	ext{-ketoglutarate} + O_2$ + 	ext{Fe}^{2+} + 	ext{Ascorbate} ightarrow 	ext{Hydroxyprolyl residue} + 	ext{Succinate} + CO_2$

Question 4

Which ECM component is primarily responsible for providing tissues with elasticity and the ability to recoil after stretching?

Accepted Answer

Elastin

Question 5

A mutation in the COL4A5 gene leads to Alport syndrome. Which of the following is a direct consequence of this mutation in the glomerular basement membrane (GBM)?

Accepted Answer

Loss of the size and charge barrier, resulting in hematuria and proteinuria

Question 6

Which of the following best explains why type IV collagen forms a mesh-like structure rather than fibrils?

Accepted Answer

Type IV collagen retains its NC1 and 7S domains, allowing lateral and end-to-end assembly into a planar network

Question 7

Which of the following is a function of proteoglycans in the extracellular matrix?

Accepted Answer

Resisting compressive forces by attracting water due to their highly negative charge

Question 8

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

Granulation tissue and blood vessels

Question 9

Which of the following best describes the role of integrins in cell-ECM adhesion?

Accepted Answer

They link the cytoskeleton to the ECM and mediate bidirectional signaling

Question 10

A fibroblast is cultured on a stiff ECM gel and shows increased proliferation compared to a soft gel. Which signaling pathway is most likely activated by matrix stiffness?

Accepted Answer

YAP/TAZ translocation to the nucleus via integrin-mediated mechanotransduction

Question 11

Which of the following best explains the molecular mechanism underlying scurvy symptoms?

Accepted Answer

Impaired hydroxylation of proline residues leads to unstable collagen triple helices

Question 12

Which of the following is a direct function of matrix metalloproteinases (MMPs) in tissue remodeling?

Accepted Answer

Degradation of collagen and gelatin during ECM remodeling

Question 13

Which of the following best describes the role of fibronectin in the ECM?

Accepted Answer

It acts as an adhesive protein, binding to collagen, integrins, and proteoglycans

Question 14

A patient with Menkes disease has defective lysyl oxidase activity. Which step in collagen maturation is most directly affected?

Accepted Answer

Formation of covalent cross-links between collagen molecules

Question 15

Which of the following best explains why hyaluronic acid is important in synovial fluid?

Accepted Answer

It increases viscosity and elasticity, lubricating the articular cartilage surfaces

Question 16

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

Accepted Answer

Inside-out signaling involves talin-mediated activation of integrin affinity, while outside-in involves ECM binding triggering intracellular cascades

Question 17

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

Accepted Answer

They allow passage of ions and small molecules for coordinated contraction

Question 18

Which of the following is a clinical consequence of excessive ECM deposition (fibrosis) in an organ?

Accepted Answer

Organ dysfunction due to stiffening and loss of normal architecture

Question 19

Which of the following best explains why a monoclonal antibody against desmoglein-1 causes skin blisters but not oral blisters?

Accepted Answer

Oral mucosa expresses both desmoglein-1 and desmoglein-3, allowing compensation

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

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