UNC Biol 205 Exam 2 Questions With Verified Answers

UNC Biol 205 Exam 2 Questions With Verified Answers when cells respond to an extracellular signal, they most often convert the information carried by this molecule from one form to another. What is this process called? - answersignal transduction When does signal transduction begin? - answerwhen the receptor on a target cell recieves and incoming extracellular signal and then produces intracellular signaling molecules that alter cell behavior extracellular signal molecules, released locally example: inflammation regulation at site of infection - answerparacrine extracellular signalling molecules secreted throughout the body (through a reservoir: blood, plant sap) example: hormones - answerendocrine T/F? Each receptor triggers one particular type of cell behavior, for example, activating gene expression - answerFalse explain: effect of a signal molecule has on a cell depends on the receptors to which the molecule bind and on the intracellular signaling pathways and effector proteins that are activated downstream. A SINGLE RECEPTOR could, for example, activate metabolic enzymes and boost the expression of metabolic genes T/F? Each receptor is generally activated by only one type of signal molecule - answerTrue explain: Small molecules like acetylcholine, for example, usually bind to a pocket formed by amino acids from several transmembrane segments of the receptor. These amino acids form noncovalent interactions with the signal molecule, allowing the receptor to recognize and bind specifically to its signal. Positive feedback in signal regulation - answercan generate an abrupt, all-or-none response in which the cell moves from ignoring a signal to responding to it very strongly Which is true of the GTP-binding proteins that participate in intracellular signaling? Choose one: Only monomeric GTP-binding proteins relay messages from G-protein-coupled receptors. G-protein-coupled receptors interact with all types of GTP-binding proteins. Only trimeric GTP-binding proteins relay messages from G-protein-coupled receptors. Only trimeric GTP-binding proteins interact with guanine nucleotide exchange factors (GEFs). Only trimeric GTP-binding proteins participate in intracellular cell signaling. - answerOnly trimeric GTP-binding proteins relay messages from G-protein-coupled receptors. explain: several varieties of G proteins. each is specific for a particular set of receptors and for a particular set of target enzymes or ion channels in the plasma membrane Why does nitric oxide act as a paracrine signal that affects only neighboring cells? - answerit is rapidly converted to nitrites and nitrates in the extracellular fluid explain: reaction with oxygen and water in the extracellular environment converts NO into nitrates and nitrites within seconds of its release by the cells that produce it Signaling via a GPCR ceases when what condition occurs? - answerThe alpha-subunit hydrolyzes its bound GTP