week 11

Which statement about positive feedback regulation is accurate? A. Positive feedback regulation can generate an abrupt, all-or-none response in which the cell moves from ignoring a signal to responding to it very strongly. B. Positive feedback is rare in biological systems. C. In positive feedback, a molecular switch enhances the response to a signal by activating a component that lies downstream in the pathway. D. In positive feedback, a downstream component acts to inhibit an earlier component in the pathway to diminish the response to the initial signal. E. Positive feedback can generate responses that oscillate on and off as the activities or concentrations of the participating components rise and fall.

A. Positive feedback regulation can generate an abrupt, all-or-none response in which the cell moves from ignoring a signal to responding to it very strongly.

During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________ signaling. A. contact-dependent B. neuronal C. endocrine D. paracrine

A. contact-dependent

Many of the extracellular signal molecules that regulate inflammation are released locally at the site of infection. What form of cell-cell signaling is being used? A. paracrine B. endocrine C. contact-dependent D. neuronal

A. paracrine

Which of the following statements pertaining to signal transduction is TRUE? A. Any foreign substance that binds to a receptor will induce the same cellular response as the molecule that physiologically (normally) binds to that receptor. B. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. C. To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. D. A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response.

B. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.

Which of the following statements about G-protein-coupled receptors (GPCRs) is FALSE? A. GPCRs are found in yeast, mice, and humans. B. The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains. C. GPCRs are used in endocrine, paracrine, and neuronal signaling. D. GPCRs are the largest family of cell-surface receptors in humans.

B. The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains. (always has 7)

You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells? A. addition of a drug that prevents GTP hydrolysis by Gα B. addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive C. addition of a drug that mimics the ligand of ERC1 D. addition of a drug that activates adenylyl cyclase

B. addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive

Foreign substances like nicotine, morphine, and menthol exert their initial effects by A. killing cells immediately, exerting their physiological effects by causing cell death. B. interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus. C. removing cell-surface receptors from the plasma membrane. D. diffusing through cell plasma membranes and binding to transcription factors to change gene expression.

B. interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus.

The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by A. activating an intracellular protein kinase. B. activating a G protein. C. diffusing into cells and stimulating the cyclase directly. D. activating a receptor tyrosine kinase.

C. diffusing into cells and stimulating the cyclase directly.

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? A. signal amplification B. signal integration C. signal transduction D. signal detection

C. signal transduction

Which statement about cell signaling is correct? A. All extracellular signal molecules act by binding to receptors on the cell surface. B. Each type of extracellular signal molecule induces the same response in all target cells. C. All cell types are able to respond to the same set of signal molecules. D. Each receptor is generally activated by only one type of signal molecule. E. Each receptor triggers one particular type of cell behavior, for example, activating gene expression.

D. Each receptor is generally activated by only one type of signal molecule.