Chapter 9: Cell Communication Flashcards
What are the three stages of cell signaling?
Reception (signal binding), Transduction (signal relay), Response (cellular action).
Define ligand.
A signaling molecule (e.g., hormones, neurotransmitters) that binds to a receptor to initiate signaling.
Compare cell-surface receptors vs. intracellular receptors.
Cell-surface: Bind hydrophilic ligands (e.g., insulin, adrenaline).
Intracellular: Bind hydrophobic ligands (e.g., steroid hormones) inside the cell.
What are G-protein-coupled receptors (GPCRs)?
Transmembrane receptors that activate G-proteins (e.g., adrenaline receptor).
Describe receptor tyrosine kinases (RTKs).
Receptors that dimerize and phosphorylate tyrosine residues to trigger signaling cascades (e.g., insulin receptor).
What is a ligand-gated ion channel?
A receptor that opens/closes in response to ligand binding, allowing ion flow (e.g., acetylcholine receptor in neurons).
What is a second messenger? Give examples.
Small molecules that relay signals inside cells (e.g., cAMP, IP₃, Ca²⁺).
Explain the cAMP pathway.
Ligand binds GPCR → activates G-protein.
G-protein activates adenylyl cyclase → produces cAMP.
cAMP activates protein kinase A (PKA) → phosphorylates target proteins.
What is a phosphorylation cascade?
A series of kinase enzymes that sequentially phosphorylate and activate each other (e.g., MAP kinase pathway).
How does the IP₃/DAG pathway work?
GPCR activates phospholipase C → splits PIP₂ into IP₃ (triggers Ca²⁺ release) and DAG (activates protein kinase C).
What role does Ca²⁺ play in signaling?
Acts as a second messenger (e.g., muscle contraction, neurotransmitter release).
How do cells amplify signals?
One signal molecule activates multiple relay molecules (e.g., one epinephrine → many cAMP → many glycogen breakdown enzymes).
What are possible cellular responses to signals?
Gene expression, enzyme activation, cytoskeletal changes, apoptosis.
How do signaling pathways regulate gene expression?
Kinases phosphorylate transcription factors (e.g., CREB binds DNA when activated by cAMP).
What is apoptosis?
Programmed cell death (e.g., removal of webbed fingers during development).
Describe the role of caspases in apoptosis.
Proteases that dismantle cell components (activated by mitochondrial cytochrome c release).
How do yeast cells communicate during mating?
Release pheromones that bind GPCRs on neighboring cells, triggering mating filament growth.
What is quorum sensing in bacteria?
Bacteria secrete autoinducers to coordinate group behaviors (e.g., biofilm formation) based on population density.
What is signal transduction crosstalk?
Integration of multiple pathways (e.g., insulin and adrenaline signaling regulating blood glucose).
How do mutations in signaling pathways cause cancer?
Oncogenes (e.g., mutated Ras) or defective tumor suppressors (e.g., p53) lead to uncontrolled cell division.
What is the role of scaffolding proteins?
Organize signaling components into complexes for efficient transduction (e.g., MAP kinase scaffolds).
How does the NF-κB pathway work?
Activated by cytokines or stress → releases NF-κB to nucleus → triggers inflammation/immune responses.
What is the role of receptor endocytosis?
Terminates signaling by internalizing receptors (e.g., EGFR internalization).
