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Membrane Bound Receptors and Secondary Messengers quiz #1

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  • Describe the steps of the cyclic AMP (cAMP) signaling cascade initiated by an amino acid-based hormone binding to a G protein-coupled receptor (GPCR).
    The hormone binds to a GPCR on the cell membrane, activating a G protein. The G protein activates adenylate cyclase, which converts ATP to cyclic AMP (cAMP). cAMP then activates protein kinase A, which phosphorylates proteins, leading to a cellular response.
  • What is signal amplification in the context of secondary messenger systems, and at which steps does it occur in the cAMP pathway?
    Signal amplification is when one molecule in a signaling pathway activates multiple downstream molecules, increasing the overall signal. In the cAMP pathway, amplification occurs when one GPCR activates multiple G proteins, one adenylate cyclase produces many cAMP molecules, and one protein kinase A phosphorylates many target proteins.
  • How can the same hormone, such as epinephrine, produce different effects in different tissues?
    The same hormone can bind to different types of GPCRs in different tissues, activating different G proteins and secondary messengers. This leads to different signaling cascades and cellular responses, depending on the receptor type, secondary messenger, and proteins present in the cell.
  • Compare the roles of cAMP, DAG, and IP3 as secondary messengers in hormone signaling.
    cAMP activates protein kinase A, leading to phosphorylation of proteins. DAG activates protein kinase C, which phosphorylates a different set of proteins. IP3 causes the release of calcium ions from intracellular stores, which can activate other kinases and cellular responses.
  • Explain how GPCRs contribute to the specificity of hormone signaling in target cells.
    GPCRs are specific to certain hormones, and different cells express different types of GPCRs. This specificity ensures that only target cells with the appropriate receptor respond to a given hormone, and the type of GPCR determines the signaling cascade and cellular response.
  • What are the main steps in the cyclic AMP (cAMP) signaling cascade initiated by an amino acid-based hormone binding to a GPCR?
    The hormone binds to a GPCR, activating a G protein, which then activates adenylate cyclase to convert ATP to cAMP. cAMP activates protein kinase A, which phosphorylates proteins, leading to a cellular response.
  • At which steps does signal amplification occur in the cAMP pathway, and what is signal amplification?
    Signal amplification is when one molecule in a pathway activates multiple downstream molecules, increasing the signal. In the cAMP pathway, amplification occurs when one GPCR activates multiple G proteins, one adenylate cyclase produces many cAMP molecules, and one protein kinase A phosphorylates many target proteins.
  • How can the same hormone, such as epinephrine, produce different effects in different tissues?
    The same hormone can bind to different types of GPCRs in different tissues, activating different G proteins and secondary messengers. This leads to different signaling cascades and cellular responses depending on the receptor type and proteins present in the cell.
  • How do cAMP, DAG, and IP3 function as secondary messengers in hormone signaling?
    cAMP activates protein kinase A, leading to phosphorylation of proteins; DAG activates protein kinase C, which phosphorylates a different set of proteins; and IP3 causes the release of calcium ions from intracellular stores, which can activate other kinases and cellular responses.
  • How do GPCRs contribute to the specificity of hormone signaling in target cells?
    GPCRs are specific to certain hormones, and different cells express different types of GPCRs. This ensures that only target cells with the appropriate receptor respond to a given hormone, and the type of GPCR determines the signaling cascade and cellular response.
  • How does hormone therapy reduce the interaction of hormones with target cells at the membrane level?
    Hormone therapy can reduce the interaction of hormones with target cells by decreasing the binding of hormones to their specific membrane-bound receptors, such as G protein-coupled receptors (GPCRs). This prevents the initiation of signaling cascades and secondary messenger systems (like cyclic AMP, DAG, or IP3), thereby reducing the cellular response to the hormone.