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Questions and Answers
Which of the following molecules primarily interact with intracellular receptors?
Which of the following molecules primarily interact with intracellular receptors?
Extracellular receptors are typically inactive without their respective signal molecules.
Extracellular receptors are typically inactive without their respective signal molecules.
True
Name one of the two important molecular switches involved in cell signaling.
Name one of the two important molecular switches involved in cell signaling.
Phosphorylation or GDP/GTP binding
Intracellular receptors are located in the ______ or nucleus.
Intracellular receptors are located in the ______ or nucleus.
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Match the following types of receptors with their characteristics:
Match the following types of receptors with their characteristics:
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What is a common response of multicellular organisms to extracellular signal molecules?
What is a common response of multicellular organisms to extracellular signal molecules?
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Intracellular receptors are typically associated with hydrophilic signal molecules.
Intracellular receptors are typically associated with hydrophilic signal molecules.
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What are the two types of receptors mentioned that interact with signal molecules?
What are the two types of receptors mentioned that interact with signal molecules?
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Signal molecules activate cell signaling at concentrations of less than or equal to _____ M.
Signal molecules activate cell signaling at concentrations of less than or equal to _____ M.
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Match the following types of signaling with their descriptions:
Match the following types of signaling with their descriptions:
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What primarily dictates the speed of a cell's response to extracellular signals?
What primarily dictates the speed of a cell's response to extracellular signals?
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All cells respond the same way to the same extracellular signal molecule.
All cells respond the same way to the same extracellular signal molecule.
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What types of changes do rapid responses to extracellular signals typically involve?
What types of changes do rapid responses to extracellular signals typically involve?
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What do G-protein-coupled receptors (GPCRs) directly activate?
What do G-protein-coupled receptors (GPCRs) directly activate?
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GPCRs function solely by activating ion channels directly.
GPCRs function solely by activating ion channels directly.
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Name one type of cell-surface receptor protein mentioned in the content.
Name one type of cell-surface receptor protein mentioned in the content.
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GPCRs are involved in transmitting extracellular signals such as _____ and _____ .
GPCRs are involved in transmitting extracellular signals such as _____ and _____ .
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Match the following receptor types with their primary function:
Match the following receptor types with their primary function:
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What is the role of the G-α-subunit of the trimeric G protein?
What is the role of the G-α-subunit of the trimeric G protein?
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Some GPCRs can regulate ion channels in muscle and nerve cells.
Some GPCRs can regulate ion channels in muscle and nerve cells.
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What are the second messengers produced by adenylyl cyclase?
What are the second messengers produced by adenylyl cyclase?
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Study Notes
Cell Communication Overview
- Cells communicate via signals, which alter cell behavior.
- Unicellular organisms respond to extracellular signals leading to altered cell behavior.
- Multicellular organisms respond to signals by altering metabolism, tissue growth, differentiation, protein synthesis, secretion, intracellular and extracellular composition.
- Signal molecules bind to specific receptors on/in target cells.
- Signal transduction converts extracellular ligand-binding events into intracellular signals that change target cell behaviour.
Signal Molecules & Receptors
- Signal molecules (ligands) can be small (hydrophobic) or large molecules (hydrophilic).
- Different signal molecules elicit diverse responses in cells, based on the receptor and the intracellular machinery.
- Hydrophilic signal molecules bind to cell surface receptors, while hydrophobic signal molecules bind to intracellular receptors.
- Receptors can be intracellular receptors (bind to hydrophobic molecules within the cytoplasm or nucleus) or cell-surface receptors.
Speed of Response
- Speed of cell response to extracellular signals depends on the signal delivery mechanism and the target cell response.
- Rapid responses involve changes in existing proteins (allosteric changes in ion channels, protein phosphorylation).
- Slow responses involve changes in gene expression and new protein synthesis.
Different Types of Cell Responses to Extracellular Signals
- A cell's response to extracellular signals is determined by its receptors and intracellular response mechanisms.
- Cells respond differently to the same extracellular signal molecule depending on their specific receptors and intracellular machinery.
- Signal concentration influences cell responses.
Intracellular Receptors
- Intracellular receptors are located within the cytoplasm or nucleus and bind directly to hydrophobic signal molecules.
- Signal molecules enter the cell and bind to the inactive receptor, causing a change in receptor conformation and activating it.
- Examples of signal molecules that use intracellular receptors include steroids, hormones, and thyroid hormones.
Relaying Signals From Cell Surface Via Second Messengers
- Relaying signals from cell surface involves utilizing second messengers.
- Small molecules (second messengers) carry and distribute intracellular signals.
- Examples include cyclic AMP (cAMP), inositol triphosphate (IP3), and diacylglycerol (DAG).
Intracellular Mediators and Enzymatic Cascades Amplify Extracellular Signals
- Intracellular mediators (second messengers) and enzymatic cascades amplify extracellular signals leading to larger cellular responses.
- Amplification via cascades increases the strength of the signals and affects more downstream processes.
- Feedback mechanisms control the signal strength and regulate the activity of the signal transduction pathways.
Two Important Molecular Switches
- Two important molecular switches are protein phosphorylation and GDP/GTP binding.
- Protein phosphorylation is the addition of phosphate groups to proteins altering their conformation and function.
- GDP/GTP binding regulates protein activity and pathways. GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs) contribute to signaling by binding and modulating proteins.
Desensitization of a Signal
- Cells adapt to prolonged or excessive signaling through desensitization mechanisms.
- Negative feedback, delayed feed-forward, receptor inactivation, receptor sequestration, and receptor destruction are various desensitization mechanisms.
- These mechanisms prevent sustained responses to excessive signals.
Three Types of Cell-Surface Receptor Proteins
- Ion channel-coupled, G-protein-coupled, and enzyme-coupled receptors are three types of cell surface receptors.
- Ion channel-coupled receptors mediate fast transmission of signals.
- G-protein-coupled receptors act by indirectly regulating other proteins (enzymes or ion channels).
- Enzyme-coupled receptors either function as enzymes or interact with associated enzymes.
Receptor Tyrosine Kinases (RTKs)
- Ligand binding to RTKs triggers dimerization of receptor molecules, resulting in cross-phosphorylation.
- Cross-phosphorylation activates specific downstream signaling pathways.
- RTKs initiate signaling cascades that change cellular behaviour via protein phosphorylation.
MAP Kinase Signaling Module
- MAP kinase pathways are crucial signaling modules for diverse cellular responses.
- The pathways have three components (MAPKKK, MAPKK, MAPK), with kinases phosphorylating each other to activate the pathway.
- Activated MAPKs can initiate downstream signaling, affecting cell behaviour.
Parallel Intracellular Signaling Pathways
- Multiple intracellular signaling pathways can be activated by either GPCRs or RTKs creating parallel pathways.
- The activated pathways often converge on common signaling components potentially enhancing or opposing other pathways.
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Description
Explore the vital processes of cell communication in this quiz. Delve into how unicellular and multicellular organisms react to signals and the roles of signal molecules and receptors. Understand the significance of signal transduction in altering cell behavior.
