Question 1

Which component of the extracellular matrix (ECM) in animal cells is primarily responsible for resisting tensile (pulling) forces?

Accepted Answer

Collagen

Question 2

A plant cell is exposed to drought conditions. Which hormone is secreted to trigger a response in guard cells, and what is the primary effect?

Accepted Answer

Abscisic acid; closes stomata to reduce water loss

Question 3

Which structure connects adjacent plant cells and allows the passage of water, ions, and small molecules directly between their cytoplasms?

Accepted Answer

Plasmodesmata

Question 4

In animal tissues, which cell–cell attachment forms a watertight seal and is most commonly found in epithelial cells?

Accepted Answer

Tight junctions

Question 5

Which of the following best describes the function of integrins in animal cells?

Accepted Answer

They anchor the cytoskeleton to the extracellular matrix (ECM).

Question 6

A signaling molecule binds to a G-protein-coupled receptor. What is the next step in the signal transduction pathway?

Accepted Answer

The G protein exchanges GDP for GTP and becomes activated.

Question 7

Which equation best represents the osmotic pressure ($$\Pi) $$experienced by a plant cell as water enters by osmosis?

Accepted Answer

$$\Pi = CRT$$

Question 8

Which of the following is a key difference between the extracellular layers of prokaryotes and eukaryotes?

Accepted Answer

Eukaryotes have a fiber composite surrounded by a ground substance.

Question 9

Which process is most likely to be affected if a cell’s signal receptors are blocked by a drug such as a beta-blocker?

Accepted Answer

Signal reception and cellular response to hormones

Question 10

Which of the following best explains why second messengers are effective in signal transduction?

Accepted Answer

They are small molecules that diffuse rapidly and amplify the signal.

Question 11

A cell receives a lipid-soluble hormone. What is the sequence of events leading to a cellular response?

Accepted Answer

Hormone diffuses through plasma membrane, binds to intracellular receptor, hormone–receptor complex enters nucleus, changes gene expression.

Question 12

Which structure in plant cells is responsible for 'gluing' adjacent cells together?

Accepted Answer

Middle lamella

Question 13

Which of the following is a real-world example of quorum sensing in unicellular organisms?

Accepted Answer

Formation of biofilm (plaque) on teeth by bacteria

Question 14

Which of the following best describes the role of receptor tyrosine kinases (RTKs) in cell signaling?

Accepted Answer

They catalyze phosphorylation cascades inside the cell after hormone binding.

Question 15

Which of the following is NOT a function of the extracellular matrix (ECM) in animal cells?

Accepted Answer

Synthesizing DNA

Question 16

Which of the following statements about cell–cell communication is correct?

Accepted Answer

Cells can communicate over long distances using hormones.

Question 17

Which of the following best describes the concept of 'crosstalk' in cell signaling?

Accepted Answer

The integration of multiple signaling pathways to produce a coordinated cellular response.

Question 18

Which equation describes the phosphorylation of a protein by a kinase in a signal transduction pathway?

Accepted Answer

$$	ext{Protein} + 	ext{ATP} ightarrow 	ext{Protein-P} + 	ext{ADP}$$

Question 19

Which of the following is a plausible consequence if phosphatases fail to deactivate a phosphorylation cascade?

Accepted Answer

The cell will remain in an activated state, potentially leading to uncontrolled growth.

Question 20

Which of the following is a correct sequence for signal transduction via G-protein-coupled receptors?

Accepted Answer

Signal binds receptor → G protein exchanges GDP for GTP → G protein activates enzyme → Second messenger produced

Cell–Cell Interactions: Structure, Communication, and Signaling

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