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Questions and Answers
What type of signaling involves a signaling and responding cell being the same?
Which of the following best describes paracrine signaling?
Which of the following is NOT a requirement for cell signaling?
In which type of signaling do signals primarily travel through the bloodstream?
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What does PDGF stand for in the context of cell signaling?
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Which type of signaling involves a ligand binding to a receptor on a different cell?
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When a cell produces a signaling molecule and a receptor that binds to it is located on the same cell, which option describes this situation?
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Which is a primary example of contact-dependent signaling?
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What role does cAMP play in the adrenaline signaling pathway?
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What happens to the receptors when the concentration of adrenaline declines?
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How do phosphatases contribute to signal termination in the adrenaline signaling pathway?
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What triggers the kinase cascade in the MAP kinase pathway?
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What can cause excessive cell proliferation associated with some cancers?
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What effect does ligand binding have on ligand-gated ion channels?
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Which statement about insulin receptor kinases is correct?
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What is a primary consequence of Ras being constitutively bound to GTP?
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What is the primary reason that paracrine signaling may not activate the responding cell?
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How does a cell respond when surface proteins are stripped away and a specific signaling molecule is added?
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Which type of receptor is active only when a ligand is bound to it?
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Which of the following represents a mechanism of action for intracellular receptors?
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What role does cAMP serve in signaling from G protein-coupled receptors?
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In which situation would a ligand-gated ion channel typically respond?
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What is a key characteristic of receptor kinases?
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Which statement accurately describes the interaction between ligands and receptors?
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Study Notes
Cell Communication in Multicellular Life
- Signaling cell: produces the signaling molecule
- Signaling molecule: binds to the receptor on a responding cell
- Receptor protein: binds to the signaling molecule
- Responding cell: produces a response to the signaling molecule
Cell Signaling Steps
- Signaling molecule: also known as a ligand
- Signaling cell: produces the signaling molecule
- Receptor: binds to the signaling molecule
- Responding cell: receives the signal
Types of Signals
-
Endocrine signaling: long distance signaling
- Example: adrenaline, estrogen, testosterone
-
Paracrine signaling: short distance signaling
- Example: growth factors, platelet-derived growth factor (PDGF)
-
Autocrine signaling: the signaling and responding cell are the same
- Important in embryonic development
-
Contact-dependent signaling: transmembrane protein in one cell acts as a signal and binds to a receptor on another cell
- Example: Delta-Notch signaling in development
Receptors
- Receptors: proteins that bind signaling molecules
- Can be found inside or on the cell surface
- Ligand: signaling molecule that binds to the ligand-binding site of the receptor
- When a ligand binds to a receptor, the receptor undergoes a conformational change and is activated.
Intracellular Receptors
- Nonpolar molecules: can cross the membrane and bind to receptors in the cytoplasm or nucleus
- Steroid hormones: are an example of nonpolar molecules that bind to intracellular receptors
Cell-Surface Receptors
- Polar ligands: cannot cross the membrane and must bind to cell-surface receptors
- The receptor-ligand complex undergoes a conformational change and the receptor is activated
Types of Cell-Surface Receptors
- G protein-coupled receptors
- Receptor kinases
- Ion channels
G Protein-Coupled Receptors
- Inactive until bound by a ligand
- When a ligand binds, the receptor can bind to a G protein
- G protein: activated when the receptor is bound by a ligand
- Second messenger: cAMP in the case of heart muscle stimulation
Receptor Kinases
- When a ligand binds, the receptor kinase dimerizes and phosphorylates another protein
- Examples: insulin, wound healing
Ligand-Gated Ion Channels
- Alter the flow of ions across the membrane
- When a ligand binds to an ion channel, the channel opens and ions can flow across the membrane
Cell Signaling and Cancer
- Some cancers can form when a signaling molecule is overproduced or produced in altered forms
- Example: mutations that make Ras always bound to GTP can cause 30% of cancers
- Some cancers can be caused when a receptor remains bound to its ligand
- An excess of receptors can also cause cancer because there is an increase in cellular response
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Description
Explore the intricate mechanisms of cell signaling in multicellular organisms. This quiz covers various types of signals, including endocrine, paracrine, autocrine, and contact-dependent signaling. Test your knowledge on how signaling molecules and receptors facilitate communication between cells.
