Question 1

Which of the following best describes the function of tight junctions in epithelial cells?

Accepted Answer

They create a permeability barrier by sealing cells together, preventing movement of molecules between cells.

Question 2

During the epithelial-mesenchymal transition (EMT), which change in cell adhesion is most likely to occur?

Accepted Answer

Decreased expression of cadherins, resulting in loss of epithelial characteristics and increased cell motility.

Question 3

Which protein is directly responsible for linking cadherins to actin filaments in adherens junctions?

Accepted Answer

α-catenin

Question 4

A mutation in the gene encoding dystrophin is most likely to affect which cellular structure and function?

Accepted Answer

Costameres, destabilizing the attachment of muscle cells to the extracellular matrix and leading to muscular dystrophy.

Question 5

Which of the following statements about collagen is TRUE?

Accepted Answer

Collagen fibers are stabilized by hydrogen bonds involving hydroxylysine and hydroxyproline.

Question 6

Which of the following best explains why integrins are considered to 'integrate' the cytoskeleton with the extracellular matrix?

Accepted Answer

Integrins are transmembrane proteins that bind extracellular matrix molecules and connect to cytoskeletal proteins such as actin via linker proteins.

Question 7

A patient with a defect in the gene encoding claudin proteins would most likely experience which physiological problem?

Accepted Answer

Impaired paracellular ion transport across epithelial layers.

Question 8

Which of the following is a distinguishing feature of plant cell walls compared to animal extracellular matrices?

Accepted Answer

Presence of cellulose microfibrils as the main structural component.

Question 9

Which molecule is most abundant in the extracellular matrix of animal cells and is responsible for its tensile strength?

Accepted Answer

Collagen

Question 10

Which of the following best describes the role of fibronectin in cell migration?

Accepted Answer

Fibronectin acts as a bridging molecule between cells and the extracellular matrix, guiding cellular movement.

Question 11

Which of the following equations best represents the relationship between the number of collagen molecules ($$n) $$and the number of fibrils ($$f) if $$each fibril is composed of $$k$$ collagen molecules?

Accepted Answer

$$f = \frac{n}{k}$$

Question 12

Which of the following is TRUE regarding gap junctions?

Accepted Answer

They are composed of connexons, each made of six connexin subunits.

Question 13

A scientist observes that a certain tissue expresses high levels of P-cadherin. Which tissue is most likely being studied?

Accepted Answer

Placental tissue

Question 14

Which of the following best describes the function of matrix metalloproteinases (MMPs) in the extracellular matrix?

Accepted Answer

They degrade the extracellular matrix locally, allowing cells to pass through.

Question 15

Which of the following is a function of the basal lamina?

Accepted Answer

It provides a permeability barrier and structural support beneath epithelial cells.

Question 16

Which of the following best explains why glycosaminoglycans (GAGs) are important in the extracellular matrix?

Accepted Answer

They attract water and cations, forming a gelatinous matrix where collagen and elastin are embedded.

Question 17

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

Accepted Answer

Hemidesmosomes connect cells to the extracellular matrix, while desmosomes connect cells to each other.

Question 18

Which of the following best describes the role of plasmodesmata in plant cells?

Accepted Answer

They are cytoplasmic channels that permit direct communication between adjacent plant cells.

Question 19

Which of the following is TRUE regarding the synthesis of plant cell walls?

Accepted Answer

The middle lamella is the first structure laid down, holding adjacent cells together.

Question 20

Which of the following best describes the relationship between integrin clustering and anchorage-dependent growth?

Accepted Answer

Integrin clustering activates intracellular signaling pathways necessary for cell division when cells are attached to a substratum.

Cell Adhesions, Cell Junctions, and Extracellular Structures

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