Question 1

Which of the following best describes the sequence of events in cell signaling that allows an impala to escape from a cheetah, as shown in the provided images?

Accepted Answer

Signal reception → Signal transduction → Cellular response

Question 2

Which type of cell signaling involves the direct transfer of signaling molecules through gap junctions in animal cells or plasmodesmata in plant cells?

Accepted Answer

Direct cell-to-cell signaling

Question 3

A signaling molecule binds to a G protein-coupled receptor (GPCR) on the surface of a muscle cell. Which of the following is the correct sequence of events that follows?

Accepted Answer

The GPCR activates a G protein, which then activates adenylyl cyclase, leading to the production of cAMP.

Question 4

Which of the following best explains why calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$can function as effective second messengers in signal transduction pathways?

Accepted Answer

Their concentration in the cytosol is normally much lower than outside the cell, so small changes have large effects.

Question 5

A mutation causes a receptor tyrosine kinase (RTK) to be permanently active, even without a ligand. What is a likely consequence of this mutation in a cell?

Accepted Answer

Uncontrolled cell division, potentially leading to cancer

Question 6

Which of the following is a key feature of signal amplification in a phosphorylation cascade?

Accepted Answer

Each activated kinase can activate many molecules of the next kinase in the pathway

Question 7

In the context of the impala’s flight response, which enzyme is directly responsible for converting ATP to cyclic AMP ($$\mathrm{cAMP}$$)?

Accepted Answer

Adenylyl cyclase

Question 8

Which of the following statements about intracellular receptors is correct?

Accepted Answer

They are activated by small or hydrophobic molecules that can cross the plasma membrane.

Question 9

A scientist adds a drug that inhibits protein phosphatases in a cell. What is the most likely effect on signal transduction pathways involving phosphorylation cascades?

Accepted Answer

Proteins will remain phosphorylated longer, prolonging the signal.

Question 10

Which of the following best describes the role of scaffolding proteins in signal transduction?

Accepted Answer

They increase the efficiency of signal transduction by grouping together different proteins involved in the same pathway.

Question 11

Which of the following is an example of paracrine signaling?

Accepted Answer

A growth factor released by one cell stimulates nearby cells to divide.

Question 12

Which of the following equations correctly represents the conversion of ATP to cyclic AMP ($$\mathrm{cAMP}) by $$adenylyl cyclase?

Accepted Answer

$$\mathrm{ATP \xrightarrow{adenylyl\ cyclase} cAMP + PP_i}$$

Question 13

Which of the following is a direct result of ligand binding to a ligand-gated ion channel receptor?

Accepted Answer

The channel opens, allowing specific ions to flow across the membrane.

Question 14

A cell receives two different signals at the same time, leading to a coordinated response involving cross-talk between two pathways. What property of cell signaling does this illustrate?

Accepted Answer

Specificity and coordination of the response

Question 15

Which of the following best explains why the same signaling molecule can produce different responses in different cell types?

Accepted Answer

Different cells have different collections of proteins and pathways.

Question 16

In the context of the fight-or-flight response, which of the following is the correct sequence of molecular events leading to the breakdown of glycogen in muscle cells?

Accepted Answer

Epinephrine binds GPCR → G protein activated → Adenylyl cyclase produces cAMP → Protein kinase A activated → Glycogen phosphorylase activated

Question 17

Which of the following mechanisms ensures that a cell’s response to a signal is not permanent and can be turned off?

Accepted Answer

Inactivation mechanisms such as removal of the signaling molecule and dephosphorylation of proteins

Question 18

Which of the following best describes the function of protein kinases in signal transduction pathways?

Accepted Answer

They transfer phosphate groups from ATP to proteins, activating or deactivating them.

Question 19

Which of the following is a real-world example of endocrine (hormonal) signaling?

Accepted Answer

The release of insulin by the pancreas, which travels through the bloodstream to affect cells throughout the body

CH 11- Cell Communication: Mechanisms and Pathways in Biology

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