Question 1

Which of the following best describes the three stages of cell signaling as illustrated in the first image (epinephrine signaling in muscle cells)?

Accepted Answer

Signal reception, signal transduction, cellular response

Question 2

In the context of cell signaling, what is the primary function of a G protein-coupled receptor (GPCR) as shown in the third image?

Accepted Answer

To transmit signals from extracellular ligands to intracellular G proteins

Question 3

Refer to the sequence of images showing the GPCR pathway (images 4–7). What is the role of GTP in this signaling pathway?

Accepted Answer

GTP activates the G protein, allowing it to relay the signal to downstream enzymes

Question 4

Which step in the GPCR pathway (images 4–7) is responsible for terminating the signal, and how does it occur?

Accepted Answer

The G protein hydrolyzes GTP to GDP, inactivating itself

Question 5

In the receptor tyrosine kinase (RTK) pathway (images 8–11), what is the significance of receptor dimerization?

Accepted Answer

Dimerization brings two receptor monomers together, allowing cross-phosphorylation and activation

Question 6

How does an activated RTK (image 11) lead to multiple cellular responses?

Accepted Answer

Each phosphorylated tyrosine on the RTK acts as a docking site for different relay proteins, triggering various pathways

Question 7

Which of the following is a key difference between GPCRs and RTKs in terms of signal transduction?

Accepted Answer

RTKs can activate multiple pathways simultaneously, while GPCRs typically activate one pathway at a time

Question 8

In the ion channel receptor pathway (images 12–14), what is the immediate effect of ligand binding?

Accepted Answer

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

Question 9

Why do only certain cells, such as kidney cells, respond to the steroid hormone aldosterone (image 15)?

Accepted Answer

Only kidney cells have the specific intracellular receptor for aldosterone

Question 10

In the phosphorylation cascade shown in the last image, what is the main advantage of having multiple steps in the pathway?

Accepted Answer

Signal amplification and increased regulation at multiple points

Question 11

Which enzyme is responsible for removing phosphate groups from proteins, thereby turning off the signal in a phosphorylation cascade?

Accepted Answer

Protein phosphatase

Question 12

What is the role of second messengers such as cAMP in cell signaling?

Accepted Answer

They relay and amplify signals from receptors to target molecules inside the cell

Question 13

Which of the following best explains why epinephrine cannot activate glycogen phosphorylase in a broken cell membrane preparation?

Accepted Answer

Epinephrine requires an intact plasma membrane with functional receptors and relay molecules to initiate the signaling cascade

Question 14

Which of the following is a real-world example of a disease caused by disruption of G protein signaling?

Accepted Answer

Cholera, due to continuous activation of G proteins and overproduction of cAMP

Question 15

Which of the following is NOT a typical cellular response induced by calcium ions as second messengers?

Accepted Answer

DNA replication

Question 16

What is the function of transcription factors in the cell signaling pathway involving steroid hormones?

Accepted Answer

They bind to specific DNA sequences to regulate gene transcription

Question 17

Which of the following best describes the process of apoptosis?

Accepted Answer

Programmed cell death involving DNA fragmentation, organelle breakdown, and engulfment by phagocytes

Question 18

How do scaffolding proteins enhance the efficiency of signal transduction pathways?

Accepted Answer

They hold multiple relay proteins together, increasing the speed and specificity of signal transmission

Question 19

Which of the following is a way that a cell can terminate a signaling pathway?

Accepted Answer

Enzymatic degradation of signaling molecules or reversible ligand binding

Cell Communication and Signal Transduction Pathways (8/17/26)

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