Question 1

Which of the following best describes the primary function of collagen in the extracellular matrix (ECM) of animal cells?

Accepted Answer

Collagen forms fibers with high tensile strength, providing structural support to tissues.

Question 2

A mutation in the Sar1 gene leads to craniolenticular syndrome due to a defect in collagen secretion. What is the role of Sar1 in the cell?

Accepted Answer

Sar1 is involved in vesicle formation for transporting collagen from the endoplasmic reticulum to the Golgi apparatus.

Question 3

Which of the following ECM molecules is primarily responsible for imparting elasticity and flexibility to tissues such as skin and blood vessels?

Accepted Answer

Elastin

Question 4

Proteoglycans are composed of a core protein and multiple glycosaminoglycan (GAG) chains. Which property of GAGs is most important for their function in the ECM?

Accepted Answer

GAGs are highly sulfated and hydrophilic, attracting water and cations to form a gelatinous matrix.

Question 5

Which adhesive glycoprotein is most commonly found in the basal lamina and is essential for connecting epithelial cells to the underlying ECM?

Accepted Answer

Laminin

Question 6

Integrins are transmembrane receptors that connect the ECM to the cytoskeleton. Which sequence in ECM proteins is commonly recognized by integrins?

Accepted Answer

RGD (Arg-Gly-Asp)

Question 7

A patient with Duchenne muscular dystrophy has a mutation in the dystrophin gene. What is the consequence of this mutation at the cellular level?

Accepted Answer

Defective costamere structure, leading to unstable attachment of muscle cells to the ECM.

Question 8

Matrix metalloproteinases (MMPs) play a critical role in tissue remodeling. Which of the following best describes their function?

Accepted Answer

MMPs degrade ECM components locally, allowing cell migration and invasion.

Question 9

Which of the following best explains anchorage-dependent growth in cultured animal cells?

Accepted Answer

Cells require attachment to ECM via integrins to activate intracellular signaling pathways for cell division.

Question 10

Which of the following statements about plasmodesmata in plant cells is correct?

Accepted Answer

Plasmodesmata are cytoplasmic channels through the cell wall, allowing direct communication between adjacent plant cells.

Question 11

In the Hershey-Chase experiment, why was radioactive phosphorus ($$^{32}P) $$used to label DNA and radioactive sulfur ($$^{35}S) $$used to label protein?

Accepted Answer

Phosphorus is present in DNA but not in protein; sulfur is present in protein but not in DNA.

Question 12

Retroviruses such as HIV use reverse transcriptase to replicate. Which of the following equations best represents the process catalyzed by reverse transcriptase?

Accepted Answer

$$RNA \rightarrow DNA$$

Question 13

Which class of antiretroviral drugs directly inhibits the integration of HIV proviral DNA into the host genome?

Accepted Answer

Integrase inhibitors

Question 14

A scientist is studying the effect of fibronectin knockout in mice. Which phenotype is most likely to be observed?

Accepted Answer

Severe defects in musculature and vasculature due to impaired cell-ECM adhesion.

Question 15

Which of the following best describes the structure of collagen molecules?

Accepted Answer

Collagen molecules consist of three polypeptide chains twisted into a rigid triple helix.

Question 16

Which ECM component is most abundant in vertebrates, accounting for 25-30% of total body protein?

Accepted Answer

Collagen

Question 17

Which of the following is a major difference between hemidesmosomes and desmosomes?

Accepted Answer

Hemidesmosomes connect cells to the ECM via integrins, while desmosomes connect adjacent cells via cadherins.

Question 18

Which of the following best explains the role of integrins in cell crawling during wound healing?

Accepted Answer

Integrins anchor cells to the ECM and transmit signals to the cytoskeleton, facilitating cell movement.

Question 19

Which of the following is a function of proteoglycans in the ECM?

Accepted Answer

Proteoglycans provide a lubricating, water-rich matrix that reduces friction in joints.

Extracellular Matrix and Genetic Material: Structure, Function, and Discovery

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