Question 1

Which of the following best describes the primary structural motif found in all fibrillar collagens?

Accepted Answer

A triple helix formed by Gly-X-Y repeats, where X and Y are often proline and 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 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 of the following best explains why type IV collagen forms a mesh-like network rather than long fibrils?

Accepted Answer

Type IV collagen retains its NC1 and 7S domains, allowing lateral and end-to-end associations that create a planar mesh

Question 5

A mutation in the COL4A5 gene leads to Alport syndrome. Which organ system is most likely to be affected first, and why?

Accepted Answer

Kidneys, because the glomerular basement membrane relies on a3a4a5(IV) collagen for its filtration barrier

Question 6

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

Accepted Answer

Providing hydration and resistance to compression by attracting water via negatively charged GAGs

Question 7

A patient with Menkes disease has defective collagen cross-linking. Which step in collagen maturation is most directly affected?

Accepted Answer

Oxidative deamination of lysine residues by lysyl oxidase

Question 8

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

Accepted Answer

They mediate bidirectional signaling between the ECM and the cytoskeleton, affecting cell migration and survival

Question 9

Which of the following is a direct consequence of matrix metalloproteinase (MMP) overactivity in tissue?

Accepted Answer

Excessive degradation of collagen and ECM proteins, contributing to diseases such as osteoarthritis and cancer metastasis

Question 10

Which of the following best explains why a fibroblast on a stiff ECM proliferates more than one on a soft ECM, even with identical growth factors?

Accepted Answer

Stiff ECM increases integrin clustering and focal adhesion assembly, activating FAK/Src and YAP/TAZ signaling pathways that promote proliferation

Question 11

Which of the following is a distinguishing feature of elastin compared to collagen?

Accepted Answer

Elastin contains desmosine cross-links that allow tissues to stretch and recoil

Question 12

Which of the following cell junctions is primarily responsible for maintaining the selective permeability barrier of the blood-brain barrier?

Accepted Answer

Tight junctions (zonula occludens) composed of claudins and occludins

Question 13

A patient with pemphigus vulgaris develops oral blisters. Which molecular mechanism best explains this finding?

Accepted Answer

Autoantibodies target desmoglein-3, which is the dominant isoform in oral mucosa, leading to loss of cell-cell adhesion

Question 14

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

Accepted Answer

They allow the passage of ions and small molecules, enabling coordinated contraction of the myocardium

Question 15

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 (e.g., talin binding) that increase integrin affinity for ECM, while outside-in signaling is triggered by ECM binding and activates intracellular cascades

Question 16

Which of the following best explains the role of fibronectin in wound healing?

Accepted Answer

It acts as a provisional matrix protein, providing a scaffold for cell migration and binding to integrins, collagen, and proteoglycans

Question 17

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

Accepted Answer

Impaired organ function due to increased tissue stiffness and loss of normal architecture

Question 18

Which of the following best describes the composition and function of the basement membrane?

Accepted Answer

It is composed of type IV collagen, laminin, nidogen, and perlecan, and functions as a tissue barrier, filtration interface, and organizer of cell polarity

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

Study Guide - Practice Questions

Study Guide - Flashcards