Question 1

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

Accepted Answer

It provides structural support and helps cells stick together through a network of collagen and proteoglycans.

Question 2

Which protein is primarily responsible for the fibrous component of the animal ECM, and what is its structural organization?

Accepted Answer

Collagen; forms triple helices that assemble into fibrils.

Question 3

What is the main role of integrins in animal cells?

Accepted Answer

They anchor the cytoskeleton to the ECM by binding to cross-linking proteins such as laminins.

Question 4

Which type of cell–cell junction forms a watertight seal between adjacent animal cells and is especially important in epithelial tissues?

Accepted Answer

Tight junctions

Question 5

Desmosomes are reinforced by which cytoskeletal element, and what is their primary function?

Accepted Answer

Intermediate filaments; provide strong cell–cell adhesion.

Question 6

Cadherins are important in cell–cell adhesion because:

Accepted Answer

They bind only to cadherins of the same type, allowing specific cell–cell attachment.

Question 7

Gap junctions in animal cells allow for:

Accepted Answer

Direct communication by permitting ions and small molecules to pass between adjacent cells.

Question 8

Which of the following statements about cell signaling is correct?

Accepted Answer

Only cells with the appropriate signal receptor will respond to a particular signaling molecule.

Question 9

Lipid-soluble signaling molecules, such as steroid hormones, typically:

Accepted Answer

Diffuse through the plasma membrane and bind to receptors in the cytoplasm, often affecting gene expression.

Question 10

Which of the following best describes the process of signal transduction for lipid-insoluble signaling molecules?

Accepted Answer

They bind to cell surface receptors, which then convert the extracellular signal into an intracellular signal.

Question 11

What is the role of G-proteins in signal transduction?

Accepted Answer

They act as peripheral membrane proteins that, when activated, trigger the production of second messengers.

Question 12

Which equation correctly represents the activation and inactivation of G-proteins?

Accepted Answer

$$	ext{G protein} + 	ext{GTP} ightarrow 	ext{Active G protein}$$

Question 13

Second messengers in signal transduction pathways are effective because:

Accepted Answer

They are small molecules that diffuse rapidly and can be produced in large quantities, amplifying the signal.

Question 14

Which of the following is a key feature of enzyme-linked receptors such as receptor tyrosine kinases (RTKs)?

Accepted Answer

They directly catalyze reactions inside the cell after dimerization and autophosphorylation.

Question 15

In the RTK signaling pathway, what is the sequence of events after a hormone binds to the receptor?

Accepted Answer

Dimerization, autophosphorylation, activation of Ras, phosphorylation cascade.

Question 16

Which enzyme is responsible for removing phosphate groups from proteins during signal deactivation?

Accepted Answer

Phosphatase

Question 17

Crosstalk in cell signaling pathways allows cells to:

Accepted Answer

Integrate multiple signals, allowing one pathway to inhibit or stimulate another.

Question 18

A researcher adds a beta-blocker drug to a culture of heart cells. What is the most likely effect on cell signaling?

Accepted Answer

The drug will block the interaction between hormones and their receptors, reducing the cellular response.

Question 19

Which of the following best explains why phosphorylation cascades are important in signal transduction?

Accepted Answer

They allow for the rapid and amplified transmission of signals from the cell surface to the nucleus.

Question 20

A mutation causes a cell to produce nonfunctional Ras protein. Which process would be most directly affected?

Accepted Answer

Signal transduction via receptor tyrosine kinases (RTKs) and the phosphorylation cascade.

Cell–Cell Interactions: Structure, Communication, and Signaling

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