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Questions and Answers
What is the primary mechanism by which G-protein-coupled receptors exert their effect on target proteins?
What is the primary mechanism by which G-protein-coupled receptors exert their effect on target proteins?
Which of the following statements accurately describes the role of adenylyl cyclase in cell signaling?
Which of the following statements accurately describes the role of adenylyl cyclase in cell signaling?
What occurs following the binding of a signaling molecule to a G-protein-coupled receptor?
What occurs following the binding of a signaling molecule to a G-protein-coupled receptor?
Which molecule is most commonly involved in the signaling cascade initiated by G-protein-coupled receptors?
Which molecule is most commonly involved in the signaling cascade initiated by G-protein-coupled receptors?
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Which type of receptor directly opens an ion channel upon ligand binding?
Which type of receptor directly opens an ion channel upon ligand binding?
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What triggers many biological processes through increases in calcium levels?
What triggers many biological processes through increases in calcium levels?
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Which class of receptors primarily involves dimerisation upon signaling molecule binding?
Which class of receptors primarily involves dimerisation upon signaling molecule binding?
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What is the primary function of Ras in receptor tyrosine kinase signaling?
What is the primary function of Ras in receptor tyrosine kinase signaling?
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What describes the action of steroid hormones in the context of intracellular receptors?
What describes the action of steroid hormones in the context of intracellular receptors?
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What is produced by the adrenal glands in response to stress and primarily affects metabolism?
What is produced by the adrenal glands in response to stress and primarily affects metabolism?
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Which signaling pathway is activated by the binding of signaling molecules to G-protein coupled receptors?
Which signaling pathway is activated by the binding of signaling molecules to G-protein coupled receptors?
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What do G-protein coupled receptors primarily regulate within the cell?
What do G-protein coupled receptors primarily regulate within the cell?
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What is a key characteristic of enzyme-coupled receptors, especially receptor tyrosine kinases?
What is a key characteristic of enzyme-coupled receptors, especially receptor tyrosine kinases?
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What component is transformed during the activation of Ras by receptor tyrosine kinases?
What component is transformed during the activation of Ras by receptor tyrosine kinases?
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Which type of receptors crosses the plasma membrane and binds to intracellular receptors?
Which type of receptors crosses the plasma membrane and binds to intracellular receptors?
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What type of signaling involves hormones that are distributed throughout the body?
What type of signaling involves hormones that are distributed throughout the body?
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In which type of signaling do cells release signals that act locally on nearby cells?
In which type of signaling do cells release signals that act locally on nearby cells?
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What is the function of intracellular signaling proteins?
What is the function of intracellular signaling proteins?
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Which class of receptors opens or closes in response to the binding of a signaling molecule, thus allowing the flow of ions across the membrane?
Which class of receptors opens or closes in response to the binding of a signaling molecule, thus allowing the flow of ions across the membrane?
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What determines the specific set of signals a cell responds to in a multicellular organism?
What determines the specific set of signals a cell responds to in a multicellular organism?
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What kind of signaling occurs when a cell binds a signal molecule directly to a receptor on an adjacent cell?
What kind of signaling occurs when a cell binds a signal molecule directly to a receptor on an adjacent cell?
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Which of the following is NOT a class of cell surface receptors?
Which of the following is NOT a class of cell surface receptors?
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Which statement about molecular switches is correct?
Which statement about molecular switches is correct?
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What is the role of effector proteins in cell signaling?
What is the role of effector proteins in cell signaling?
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Which type of signal transmitter is crucial for the nervous system and muscle cell activity?
Which type of signal transmitter is crucial for the nervous system and muscle cell activity?
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Study Notes
Cell Communication
- Cells in multicellular organisms need to respond to external and internal changes, which often involves adapting or coordinating behavior.
- Cells need to send and receive signals.
- Cellular communication involves different forms of information that can require conversion from one form to another.
- Signal transduction is a process of converting a signal.
- Typical cellular communication describes the signalling cell producing a signal and this signal molecule being detected by a receptor protein on a target cell.
Signal Transmission Range
- Hundreds of different extracellular signal molecules exist, including proteins, peptides, amino acids, nucleotides, steroids, fatty acid derivatives, and dissolved gases.
- Four main ways to transfer signals between cells: endocrine, paracrine, neuronal, and contact-dependent.
Endocrine Signaling
- Hormones produced in endocrine glands are released into the bloodstream and travel to distant target cells to initiate a response.
Paracrine Signaling
- Cells release local mediators into the extracellular fluid, affecting nearby target cells.
Neuronal Signaling
- Signals are transmitted along axons to distant target cells, often via neurotransmitters released at synapses.
Contact-Dependent Signaling
- Cell-surface-bound signal molecules bind to receptor proteins on adjacent cells, initiating a response.
Cellular Responses
- Each cell type has a specific set of receptor proteins allowing it to respond only to certain extracellular signalling molecules.
- Multiple signalling molecules can interact to regulate cellular behavior.
Classes of Extracellular Signaling Molecules
- Two classes: cell-surface receptors and intracellular receptors.
- Cell-surface receptors are associated or embedded in the plasma membrane; intracellular receptors are located inside the cell (e.g. in the cytoplasm or the nucleus).
Cell Surface Receptors Relay Signals Via intracellular Signaling Pathways
- A signal from the cell surface receptor is relayed inside the target cell through intracellular signalling molecules.
- This process ultimately alters the activity of effector proteins.
Intracellular Signaling Proteins Act as Molecular Switches
- Molecular switches are turned on or off, allowing cells to reset these proteins.
- Two classes: protein phosphorylation (addition/removal of phosphate groups) and GTP-binding proteins (binding to GTP or GDP).
Cell Surface Receptors Fall Into Three Main Classes
- Ion-channel-coupled receptors -respond to binding of a signal molecule by opening or closing a channel thereby allowing the flow of ions across the membrane to change the membrane potential thus producing an electrical current.
- G-protein-coupled receptors (GPCRs) - activated receptor signals GTP binding protein (G protein) on the inside of the plasma membrane, either switching an enzyme or an ion channel on or off.
- Enzyme-coupled receptors - Receptor own enzyme activity or associates with enzymes.
G-Protein-Coupled Receptors (GPCRs)
- Most frequent targets for G proteins are the enzymes: adenylyl cyclase and phospholipase C.
- These enzymes create second messengers that are involved in intracellular signalling.
- Cyclic AMP (cAMP) is a crucial second messenger. It increases rapidly in response to extracellular signals.
- cAMP activates cyclic AMP dependent protein kinase (PKA).
- PKA affects downstream effects (e.g. glycogen breakdown in skeletal muscle).
- Other second messengers are produced by phospholipase C, such as inositol 1,4,5-trisphosphate (IP3), and diacylglycerol (DAG).
Receptors Are Often Targets For Chemicals
- Multiple chemical substances (e.g. barbiturates, nicotine, morphine) can either activate or block cell surface receptors.
Some Hormones Can Cross the Plasma Membrane and Bind Intracellular Receptors
- Steroid Hormones (e.g. cortisol) are hydrophobic molecules that pass through the plasma membrane and bind to intracellular receptors within the cytoplasm or nucleus, thus affecting gene expression.
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Description
Explore the intricate processes of cell communication, including various signaling mechanisms and the different types of extracellular signal molecules. This quiz covers the fundamentals of endocrine, paracrine, neuronal, and contact-dependent signaling pathways, essential for understanding cellular interactions in multicellular organisms.
