Multiple Choice
Which of the following statements accurately describes receptor tyrosine kinases (RTKs)?
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14. Cell Signaling
Overview of Cell Surface Receptors
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Which of the following best summarizes the function of G proteins in cell signaling?
A
They directly phosphorylate target proteins to initiate cellular responses.
B
They synthesize second messengers such as cAMP and IP3.
C
They serve as structural components of the plasma membrane.
D
They act as molecular switches that transmit signals from activated receptors to target enzymes or ion channels.
Verified step by step guidance1
Understand the role of G proteins in cell signaling: G proteins are guanine nucleotide-binding proteins that act as molecular switches in signal transduction pathways.
Recognize that G proteins are activated when a signaling molecule (ligand) binds to a G protein-coupled receptor (GPCR) on the cell surface, causing a conformational change in the receptor.
Learn that upon activation, the G protein exchanges GDP (guanosine diphosphate) for GTP (guanosine triphosphate), which enables it to interact with downstream target enzymes or ion channels.
Note that G proteins do not directly phosphorylate target proteins or synthesize second messengers. Instead, they activate or inhibit enzymes (e.g., adenylyl cyclase) that produce second messengers like cAMP or IP3.
Conclude that the primary function of G proteins is to act as molecular switches, transmitting signals from activated receptors to downstream effectors, thereby initiating specific cellular responses.
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