Cell Signaling Mechanisms and Pathways

Which type of cell signaling involves a cell producing signals that act on its own receptors?

• Paracrine signaling

• Endocrine signaling

• Autocrine signaling

• Synaptic signaling

Hormones secreted into the bloodstream to act on distant target cells are an example of what type of signaling?

• Autocrine signaling

• Paracrine signaling

• Endocrine signaling

• Direct contact signaling

How do hydrophobic signaling molecules typically enter a target cell?

• They bind to transmembrane receptors on the cell surface.

• They are actively transported across the cell membrane by pumps.

• They diffuse directly across the cell membrane and bind to intracellular receptors.

• They are engulfed by the cell through endocytosis.

What event activates a G-protein, causing its alpha subunit to separate from the beta and gamma subunits?

• The alpha subunit binds to GDP.

• The G-protein coupled receptor changes shape after ligand binding.

• The beta and gamma subunits bind to GTP.

• The G-protein is phosphorylated by an enzyme.

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What is the primary function of Diacylglycerol (DAG) in the Gq protein signaling pathway?

• Activates adenylate cyclase

• Releases calcium ions from the endoplasmic reticulum

• Activates Protein Kinase C

• Inhibits phospholipase C

How does cyclic adenosine monophosphate (cAMP) activate Protein Kinase A (PKA) in the Gs protein signaling pathway?

• It directly phosphorylates the catalytic subunit of PKA

• It binds to the regulatory subunit, causing dissociation from the catalytic subunit

• It stimulates the production of more PKA

• It inhibits the enzyme that deactivates PKA

What is the initial event that leads to the activation of Receptor Tyrosine Kinases (RTKs) after ligand binding?

• The receptor's enzyme domain directly phosphorylates target proteins

• The receptor undergoes a conformational change, opening an ion channel

• Two receptor chains dimerize and cross-phosphorylate each other

• A cytoplasmic tyrosine kinase binds and activates the receptor

What is the direct consequence of a ligand binding to an ion channel receptor?

• Activation of a G-protein

• Opening of the ion channel, allowing ion flow

• Phosphorylation of intracellular proteins

• Inhibition of adenylate cyclase