Question 1

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

Accepted Answer

It acts as a fiber composite that provides structural support and helps resist tension and compression.

Question 2

Collagen is a major fibrous component of the ECM. Which structural property of collagen allows it to resist tension in animal tissues?

Accepted Answer

Collagen consists of triple helix polypeptide chains that coalesce into fibrils, providing tensile strength.

Question 3

Which molecule is primarily responsible for the rubber-like consistency of cartilage in the ECM?

Accepted Answer

Proteoglycans

Question 4

In plant cells, what is the function of the middle lamella?

Accepted Answer

It glues adjacent plant cells together using gelatinous pectins.

Question 5

Which of the following best explains why tight junctions are important in epithelial tissues?

Accepted Answer

They form a watertight seal that prevents leakage of materials between cells.

Question 6

Desmosomes are especially abundant in which type of tissue, and what is their main function?

Accepted Answer

Epithelial and muscle tissue; to provide strong cell–cell adhesion by linking cytoskeletons

Question 7

Gap junctions in animal cells are analogous to which structure in plant cells, and what is their shared function?

Accepted Answer

Plasmodesmata; allowing direct passage of ions and small molecules between cells

Question 8

Which of the following best describes the difference between the symplast and apoplast in plant tissues?

Accepted Answer

The symplast is the shared cytoplasm connected by plasmodesmata, while the apoplast is the extracellular space.

Question 9

A researcher is studying a hormone that is secreted into the bloodstream and acts on distant target cells. Which type of signaling molecule is this, and what is a key property of such molecules?

Accepted Answer

Hormone; can travel long distances and act on target cells far from the signaling cell

Question 10

Which of the following is a correct sequence of events for a lipid-soluble signaling molecule (such as a steroid hormone) acting on a target cell?

Accepted Answer

Signal diffuses across plasma membrane → binds to cytosolic receptor → receptor-hormone complex alters gene expression

Question 11

Which of the following best describes the role of G-protein-coupled receptors in signal transduction?

Accepted Answer

They activate G proteins, which then initiate the production of second messengers to amplify the signal.

Question 12

A mutation prevents the phosphorylation of proteins inside a target cell after a signaling molecule binds to its receptor. Which type of receptor is most likely affected?

Accepted Answer

Enzyme-linked receptor

Question 13

Which of the following scenarios best illustrates the concept of signal amplification in cell signaling?

Accepted Answer

A single hormone molecule triggers the activation of many second messenger molecules, each of which activates multiple target proteins.

Question 14

Which of the following is an example of crosstalk in cell signaling pathways?

Accepted Answer

A component of one signaling pathway inhibits or stimulates a component of a different pathway, integrating multiple signals.

Question 15

A patient has a genetic disorder that causes their epithelial cells to lose their watertight seal, resulting in severe dehydration. Which cellular structure is most likely defective?

Accepted Answer

Tight junctions

Question 16

Which of the following best explains why desmosomes are critical in heart muscle tissue?

Accepted Answer

They provide strong adhesion between cells, preventing them from pulling apart during contraction.

Question 17

Which of the following equations best represents the amplification of a signal in a G-protein-coupled receptor pathway?

Accepted Answer

$$1 	ext{ signal molecule} ightarrow n 	ext{ activated G proteins} ightarrow n^2$ 	ext{ second messengers}$$

Question 18

A scientist blocks the formation of proteoglycans in the ECM of cartilage. Which property of cartilage would be most affected?

Accepted Answer

Its rubber-like consistency and ability to resist compression

Question 19

Which of the following best describes the process by which a lipid-insoluble signal leads to a change in gene expression?

Accepted Answer

The signal binds to a membrane receptor, triggering a transduction cascade that ultimately alters gene expression.

Cell–Cell Interactions: Structure, Adhesion, and Signaling

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