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General Biology: Cell Signaling and Enzyme Regulation

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Termini in questo insieme (24)

  • What is the main purpose of cell signaling?
    Cell signaling allows cells to communicate and coordinate their activities in multicellular and unicellular organisms.
  • What is paracrine signaling?
    A type of local signaling where a cell secretes local regulators that affect nearby target cells, such as growth factors.
  • What is endocrine signaling?
    Long-distance signaling where specialized cells release hormones into the bloodstream to affect distant target cells.
  • What are the three stages of cell signaling?
    Reception: signal detection; Transduction: signal conversion; Response: cellular activity triggered by the signal.
  • What happens during reception in cell signaling?
    A signaling molecule (ligand) binds specifically to a receptor, often causing a conformational change that activates the receptor.
  • Where are signal receptors located?
    On the plasma membrane for water-soluble signals or inside the cell (cytoplasm or nucleus) for small, hydrophobic signals.
  • What is a G protein-coupled receptor (GPCR)?
    A plasma membrane receptor that activates a G protein by binding GTP, initiating diverse signaling pathways.
  • How do ligand-gated ion channels function?
    They open or close in response to ligand binding, allowing specific ions to pass and trigger cellular responses.
  • What is signal transduction?
    The process of converting a signal into a cellular response through a cascade of molecular interactions.
  • What is a phosphorylation cascade?
    A series of protein kinases that phosphorylate each other, amplifying the signal and activating proteins in the pathway.
  • What role do protein phosphatases play?
    They remove phosphate groups from proteins, turning off signaling pathways and allowing reuse of kinases.
  • What are second messengers?
    Small, nonprotein molecules like cyclic AMP (cAMP) and Ca2+ that diffuse within the cell to relay signals.
  • How does cyclic AMP (cAMP) function in signaling?
    It is produced from ATP by adenylyl cyclase and activates protein kinase A to phosphorylate target proteins.
  • What is the cellular response in signaling pathways?
    Changes in gene expression or enzyme activity that alter cell behavior or metabolism.
  • What is activation energy (E_a)?
    The energy required to start a chemical reaction by breaking bonds in reactant molecules.
  • How do enzymes speed up reactions?
    By lowering the activation energy barrier without changing the overall free energy change (ΔG).
  • What is substrate specificity in enzymes?
    Enzymes bind only specific substrates at their active sites due to complementary shapes and chemical interactions.
  • What is induced fit in enzyme activity?
    The enzyme changes shape upon substrate binding to enhance interaction and catalysis.
  • What are cofactors and coenzymes?
    Nonprotein helpers required by some enzymes; cofactors can be inorganic or organic, with organic cofactors called coenzymes.
  • What is competitive inhibition?
    An inhibitor binds to the enzyme's active site, blocking substrate binding; can be overcome by increasing substrate concentration.
  • What is noncompetitive inhibition?
    An inhibitor binds to a different site, causing a conformational change that reduces enzyme activity regardless of substrate presence.
  • What is allosteric regulation?
    Regulation of enzyme activity by binding of molecules at sites other than the active site, causing activation or inhibition.
  • What is cooperativity in enzymes?
    Binding of a substrate to one subunit of a multisubunit enzyme increases the activity of other subunits.
  • What is feedback inhibition?
    The end product of a metabolic pathway inhibits an earlier enzyme to prevent overproduction and conserve resources.