Question 1

Which of the following best describes the structural difference between epithelial tissue and connective tissue?

Accepted Answer

Epithelial tissue consists of tightly packed cells with little extracellular matrix, whereas connective tissue has cells scattered within a large amount of extracellular matrix.

Question 2

What does it mean for an epithelial cell to be 'polarized', and which two domains does this polarization create?

Accepted Answer

Polarization refers to the cell having distinct apical and basal domains, each with specialized functions.

Question 3

Which cytoskeletal filament is anchored by desmosomes, and which by adherens junctions?

Accepted Answer

Desmosomes anchor intermediate filaments, while adherens junctions anchor actin filaments.

Question 4

Extracellular calcium ($$Ca^{2+}) is $$essential for cadherin function because:

Accepted Answer

It stabilizes the cadherin extracellular domain, allowing proper binding between cells.

Question 5

During the Epithelial-Mesenchymal Transition (EMT), which molecular event is most directly responsible for increased cell motility and carcinoma metastasis?

Accepted Answer

Loss of E-cadherin expression, leading to reduced cell-cell adhesion.

Question 6

Which sequence correctly outlines the three-step process by which leukocytes exit the bloodstream at sites of inflammation?

Accepted Answer

Selectin-mediated rolling, integrin activation and firm adhesion, transmigration via ICAM.

Question 7

Tight junctions in epithelial sheets serve two major functions. Which are they?

Accepted Answer

Preventing paracellular transport and maintaining cell polarity.

Question 8

Claudins are critical for paracellular transport in tight junctions because:

Accepted Answer

They form channels that selectively allow ions and small molecules to pass between cells.

Question 9

Which statement best describes the structure of a gap junction channel?

Accepted Answer

It is formed by two connexons, each made of six connexin proteins, creating a channel between adjacent cells.

Question 10

Which type of molecule can pass through gap junction channels, and what is the invertebrate analog of connexin?

Accepted Answer

Ions and small metabolites; the analog is innexin.

Question 11

Which of the following is NOT a main class of molecules found in the animal extracellular matrix (ECM)?

Accepted Answer

Actin

Question 12

Collagen, elastin, and proteoglycans/GAGs each have distinct structural properties. Which statement is correct?

Accepted Answer

Collagen provides tensile strength, elastin provides elasticity, and proteoglycans provide hydration and resistance to compression.

Question 13

Fibronectin anchors cells to the ECM via its RGD sequence. What does 'RGD' stand for, and why is it important?

Accepted Answer

Arginine-Glycine-Aspartic acid; it is recognized by integrins to mediate cell-ECM adhesion.

Question 14

Integrins connect to the cytoskeleton differently in focal adhesions versus hemidesmosomes. Which is correct?

Accepted Answer

In focal adhesions, integrins connect to actin filaments; in hemidesmosomes, they connect to intermediate filaments.

Question 15

Which sequence correctly lists the three structural layers of a plant cell wall from outermost to innermost?

Accepted Answer

Middle lamella, primary wall, secondary wall

Question 16

Plasmodesmata allow direct communication across rigid plant cell walls. Which structure forms the central core of a plasmodesma?

Accepted Answer

Desmotubule

Question 17

A patient with a genetic defect in claudin proteins is likely to experience which physiological problem?

Accepted Answer

Impaired paracellular transport leading to loss of selective ion permeability in epithelial tissues.

Question 18

If a carcinoma cell undergoes EMT and loses E-cadherin, which change is most likely to occur?

Accepted Answer

The cell will gain increased motility and invasive potential.

Question 19

Which combination of proteins is involved in regulating adherens junctions and responding to mechanical tension?

Accepted Answer

α-catenin, β-catenin, vinculin, and p120 catenin

Cell Biology Study Guide: Tissue Structure, Cell Junctions, and ECM

Study Guide - Practice Questions

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