BIOS 1700 Chapter 9 Cell Signaling

Which type of cell signaling generally occurs between cells that are distant from each other? A. All of these choices are correct. B. autocrine C. paracrine D. endocrine

D. endocrine

Growth factors such as platelet-derived growth factor (PDGF) function in: A. paracrine signaling. B. autocrine signaling. C. endocrine signaling. D. contact-dependent signaling.

A. paracrine signaling

A researcher is studying a mutant eukaryotic cell that has a defect in its adrenaline signaling G protein-coupled receptor. In these cells, he notices that even though adrenaline can bind to its G protein-coupled receptor, nothing happens. What could the mutation in these cells disrupt? A. All of these choices are correct. B. The mutation might prevent protein kinase A (PKA) from binding to cAMP. C. The mutation might prevent the G protein-coupled receptor from undergoing a conformational change upon the binding of its ligand. D. The mutation might prevent G protein α subunit from binding to GTP. E. The mutation might prevent the activation of adenylyl cyclase.

A. All of these choices are correct.

Ligand binding to a receptor kinase results in: A. All of these choices are correct. B. binding of cytoplasmic signaling molecules. C. receptor dimerization. D. phosphorylation of the cytoplasmic domain of the receptor.

A. All of these choices are correct.

Second messengers: A. All of these choices are correct. B. play a role in activation of intracellular signal transduction. C. are removed in order to terminate a cellular signaling response. D. amplify the effects of the signal. E. are small intracellular molecules that participate in signal transduction.

A. All of these choices are correct.

What happens to the α (alpha) subunit of a G protein when bound GTP is replaced with GDP? A. All of these choices are correct. B. It no longer activates an effector protein. C. It re-associates with the G protein-coupled receptor. D. It reassembles with the β (beta) and γ (gamma) subunits.

A. All of these choices are correct.

What is a growth factor? A. All of these choices are correct. B. a signaling molecule involved in paracrine signaling C. a soluble molecule that can alter gene expression in a cell D. a small protein that influences cell growth and division

A. All of these choices are correct.

Which types of cellular activities can be a response to cell signaling? A. All of these choices are correct. B. Gene expression patterns are changed. C. Cell division is triggered. D. Enzyme activities are changed. E. Cell signals are released to communicate with other cells.

A. All of these choices are correct.

What is the role of signal transduction in cell signaling? A. Signal transduction connects the activation of the receptor to the cellular response. B. Signal transduction helps end the signaling process by eliminating or deactivating signaling molecules from the cell. C. Signal transduction involves the binding of the signal molecule to the receptor, causing the receptor to change shape and activity. D. Signal transduction occurs when gene expression changes, leading to the production of new cellular proteins.

A. Signal transduction connects the activation of the receptor to the cellular response.

Why don't steroid hormones bind to transmembrane cell-surface receptors? A. Steroid hormones are nonpolar and therefore are able to cross the cell's plasma membrane, binding to receptors inside the cell. B. Steroid hormones don't require receptors because they bind directly to DNA. C. Steroid hormones are not signaling molecules. D. Steroid hormones are nonpolar and therefore cannot bind to receptors.

A. Steroid hormones are nonpolar and therefore are able to cross the cell's plasma membrane, binding to receptors inside the cell.

During the signal transduction process, the signal often triggers a signal transduction cascade. For example, a single activated receptor can activate hundreds of protein A molecules. Each activated protein A molecule activates hundreds of protein B molecules, and so on, until a cellular response occurs. What purpose does this cascade serve? A. The cascade serves to amplify the signal so one activated receptor can have a significant response. B. Having several intermediates allows for greater control of the response. C. Having a cascade allows the cell to respond to different signals. D. The cascade makes signaling easier to shut off or terminate.

A. The cascade serves to amplify the signal so one activated receptor can have a significant response.

Imagine that a researcher is studying the embryonic development of mice that do not express the signal molecule Delta. What will likely be true of these mice? A. These mice will have fewer glial cells compared to their normal counterparts. B. These mice will have fewer neurons compared to their normal counterparts. C. These mice will have more glial cells compared to their normal counterparts. D. These mice will have more neurons compared to their normal counterparts.

A. These mice will have fewer glial cells compared to their normal counterparts.

What is the cell's likely response to ligand binding to a steroid receptor located in the nucleus? A. a change in gene expression B. activation of a kinase C. initiation of a signal transduction pathway D. change in ion transport

A. a change in gene expression

Which one of the following would be found inside the cell and not on the cell surface-type? A. a steroid receptor B. a G protein-coupled receptor C. a ligand-gated receptor D. a receptor kinase

A. a steroid receptor

Where would you expect to find the receptor for a nonpolar ligand? A. either in the nucleus of the cell or in the cytosol B. only in the nucleus of the cell C. only in the cytosol D. on the cell surface

A. either in the nucleus of the cell or in the cytosol

Which signaling system involves the longest distance between release of a signaling molecule and activation of a receptor? A. endocrine B. contact-dependent C. paracrine D. autocrine

A. endocrine

Cell signaling over a long distance is known as: A. endocrine signaling. B. autocrine signaling. C. paracrine signaling. D. contact-dependent signaling.

A. endocrine signaling.

The presence of excess epidermal growth factor (EGF) receptors can result in: A. excessive cell division. B. normal cell division. C. diminished cell division.

A. excessive cell division.

Ras is a type of G protein because it: A. is only active when it binds GTP. B. responds to the activation of G protein-coupled receptors. C. triggers the formation of cyclic AMP (cAMP). D. All of these choices are correct.

A. is only active when it binds GTP.

In the developing nervous system, delta cells display on their surface the protein Delta, which interacts with and activates the Notch protein present on neighboring Notch cells. What is the developmental fate of these two cell types? A. Both cell types become neurons because both cells are in the nervous system. B. Delta cells become neurons, and the activation of Notch causes neighboring cells to become glial cells. C. Delta cells become glial cells, and the activation of Notch causes neighboring cells to become neurons.

B. Delta cells become neurons, and the activation of Notch causes neighboring cells to become glial cells.

What is the very first effect of ligand binding to a G protein-coupled receptor? A. an exchange of GTP in place of GDP on the α (alpha) subunit of the G protein B. a conformational change in the cytoplasmic domain of the receptor C. the release of the α (alpha) subunit of the G protein D. the activation of an effector protein

B. a conformational change in the cytoplasmic domain of the receptor

Cell signaling between two nerve cells can be thought of as an example of paracrine signaling because: A. a receptor is activated. B. the cells are in close proximity. C. the responding cell releases more signaling molecule (neurotransmitter). D. a signaling molecule (neurotransmitter) is released.

B. the cells are in close proximity.

Inactivation of a cell-surface receptor depends on: A. the binding affinity of the receptor. B. the release of the ligand from the receptor ligand binding site. C. the concentration of ligand surrounding the cell. D. the activity of phosphatases in the cytosol.

B. the release of the ligand from the receptor ligand binding site.

Recall from the text in the example of cell communication in Streptococcus pneumoniae that the rate of DNA uptake by pneumococcal cells increases sharply when they are at high density, due to changes in gene expression brought about by signaling between cells. If the pneumococcal cells did not express receptor protein, how would the rate of DNA uptake be affected when the cells reach high density? A. There would be a decrease in the rate of DNA uptake. B. There would be a smaller than normal increase in the rate of DNA uptake. C. There would be no increase in the rate of DNA uptake. D. There would be a larger than normal increase in the rate of DNA uptake.

C. There would be no increase in the rate of DNA uptake.

Many scientists use chemical inhibitors to interfere with normal signaling pathways within eukaryotic cells. If such inhibitors are large, nonpolar molecules, what is the likely method of action of these chemical inhibitors? A. These chemical inhibitors likely enter eukaryotic cells and interfere with components of the signal transduction pathway. B. These chemical inhibitors likely function in the cytoplasm, where they interfere with the termination of signaling, so eukaryotic cells can't process new signals. C. These chemical inhibitors likely bind to receptors on the cell surface and interfere with receptor activation or signal-receptor binding. D. These chemical inhibitors likely enter the nucleus and prevent the transcription of the pathway of interest's target genes.

C. These chemical inhibitors likely bind to receptors on the cell surface and interfere with receptor activation or signal-receptor binding.

What is one of the possible cellular responses following activation of the MAP kinase pathway? A. both the activation of adenylyl cyclase and the formation of second messengers B. the formation of second messengers in the cytosol C. a change in gene expression resulting in cell division D. the activation of adenylyl cyclase

C. a change in gene expression resulting in cell division

The activation of protein kinase A (PKA) by cyclic AMP (cAMP) binding likely occurs because of: A. the binding of GTP to protein kinase A (PKA). B. the activity of a phosphatase. C. a conformational change to protein kinase A (PKA). D. the phosphorylation of protein kinase A (PKA).

C. a conformational change to protein kinase A (PKA).

Which type of protein adds a phosphate group to another molecule? A. G protein B. phosphorylase C. kinase D. phosphatase

C. kinase

Which of the following is a cellular response to signal transduction? A. a change in the proteins found in the cytosol B. a change in the activity of an enzyme C. the release of signaling molecules from the cell D. All of these choices are correct.

D. All of these choices are correct.

Which statement is true regarding neurotransmitters? A. Neurotransmitters commonly are released into the bloodstream to affect cells throughout the body. B. Like Delta or Notch, neurotransmitters are usually attached to the cell surface. C. Neurotransmitters are usually steroids that pass through cell membranes. D. Neurotransmitters are typically dispersed over small distances

D. Neurotransmitters are typically dispersed over small distances

A researcher introduces a large polar signaling molecule produced by bacteria to eukaryotic cells that she is culturing in the laboratory. Remarkably, she notices that the signaling of the bacteria results in an increase in eukaryotic gene expression. How is this possible? A. This signaling is likely a steroid hormone that activates receptors in the eukaryotic cells. B. This prokaryotic signal likely travels directly into eukaryotic cells and acts as a transcription factor. C. This gene expression is likely from prokaryotic genes present in the genome of the eukaryotic cells. D. This signal is likely similar in structure to ligands utilized by eukaryotic cells.

D. This signal is likely similar in structure to ligands utilized by eukaryotic cells.

Which type of cell-surface receptor undergoes changes in phosphorylation in response to binding of its ligand? A. a ligand-gated ion channel B. both the G protein-coupled receptor and the receptor kinase C. a G protein-coupled receptor D. a receptor kinase

D. a receptor kinase

In the context of cell signaling, to what does the term ligand refer? A. a type of gated channel B. the proteins activated as part of a signal transduction pathway C. the extracellular domain of a receptor protein D. a signaling molecule that binds to the receptor

D. a signaling molecule that binds to the receptor

The signaling molecule involved in contact-dependent cell signaling is: A. a small soluble peptide B. a growth factor C. a neurotransmitter D. a transmembrane protein.

D. a transmembrane protein.

Mammalian steroid hormones are signaling molecules that function in which type of cell signaling? A. paracrine B. autocrine C. All of the answers are correct D. endocrine

D. endocrine

Cellular responses that result from receptor kinase activation tend to: A. involve changes in metabolism. B. involve ion channels. C. be short term. D. involve changes in gene expression.

D. involve changes in gene expression.

In many signaling pathways, once a signaling molecule binds to a receptor, the receptor becomes phosphorylated. This initial phosphorylation step best demonstrates: A. termination. B. cellular response. C. signal transduction. D. receptor activation. E. either cellular response or signal transduction.

D. receptor activation.

The ability of a specific tissue or organ to respond to the presence of a hormone is dependent on: A. the location of the tissue or organ with respect to the circulatory path. B. nothing; all hormones of the body are able to stimulate all cell types because hormones are powerful and nonspecific. C. the membrane potential of the cells of the target organ. D. the presence of the appropriate receptors on the cells of the target tissue or organ.

D. the presence of the appropriate receptors on the cells of the target tissue or organ.

Which is a true statement about receptors that are localized to the nucleus? A. They move through a nuclear pore. B. They carry a nuclear-localization signal. C. They are synthesized in the cytosol. D. They bind nonpolar ligands. E. All of the answers are correct

E. All of the answers are correct

Which signaling molecules would you expect to travel the longest distance in the human body? A. neurotransmitters B. PDGF (platelet derived growth factor) C. Notch D. Delta E. testosterone

E. testosterone

T/F: A cell can only respond to signals from other cells, not from the physical environment.

False

T/F: Most ligands form covalent bonds with their associated receptors; these complexes are more or less permanent and can only be broken through the hydrolysis of ATP.

False

T/F: Cancer is a disease of cell division.

True

T/F: G proteins of G protein-coupled receptors are often made up of three subunits: alpha, beta and gamma.

True

T/F: Signaling pathways have been conserved in a wide range of organisms.

True