Chapter 11

The source of phosphate for a phosphorylation cascade is ___. a. ATP b. GTP c. Protein phosphatase d. cAMP e. Protein kinase

a. ATP

which of the following is a likely explanation of why natural selection favored the evolution of signals for sexual reproduction? a. Even in the simplest organisms, sexual reproduction required several coordinated responses by cells. b. Multicellular eukaryotes required signals that were responded to by multiple organ systems c. Cells of several kinds of mating types needed to sort themselves to allow self-recognition d. Rooted plants required chemical diffusible signals that could travel throughout the organism e. Hormones required a mechanism for introducing changes in their target issues.

a. Even in the simplest organisms, sexual reproduction required several coordinated responses by cells.

Nitric oxide is unusual among animal signal molecules in that it_____ a. Is a gas b. Acts by directly binding to DNA c. Enters the cell via a protein channel d. Binds to membrane receptors and cytoplasm receptors e. Activates proteins by removing phosphate

a. Is a gas

Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP? a. It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane. b. It could activate only the epinephrine system. c. It would be able to carry out reception and transduction but would not be able to respond to a signal. d. It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane. e. It would employ a transduction pathway directly from an external messenger.

a. It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

Apoptosis involves all but which of the following? a. Lysis of the cell b. Activation of cellular enzymes c. Fragmentation of the DNA d. Cell-signaling pathways e. Digestion of cellular contents by scavenger cells

a. Lysis of the cell

The general name for an enzyme that transfers phosphates groups from ATP to a protein is___. a. Protein kinase b. Protein phosphatase c. Protein dehydrogenase d. Protein cyclase e. Peptidase

a. Protein kinase

cAMP usually directly activates ___. a. Protein kinase A b. G proteins c. Adenylyl cyclase d. Receptor tyrosine kinases e. Phosphodiesterase

a. Protein kinase A

cAMP usually directly activates ____. a. Protein kinase A b. G proteins c. Phosphodiesterase d. Receptor tyrosine kinase

a. Protein kinase A

Consider this pathways: epinephrine--> G protein-coupled receptor --> G protein --> adenylyl cyclase--> cAMP. Identify the second messenger. a. cAMP b. G protein c. GTP d. adenylyl cyclase e. G protein-coupled receptor

a. cAMP

The activation of receptor tyrosine kinases is characterized by a. dimerization and phosphorylation b. dimerization and IP3 binding c. a phosphorylation cascade d. GTP hydrolysis e. channel protein shape change

a. dimerization and phosphorylation

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to a. the active site of an allosteric enzyme that binds to a specific substrate. b. tRNA specifying which amino acids are in a polypeptide. c. a metabolic pathway operating within a specific organelle. d. an enzyme having an optimum pH and temperature for activity. e. an antibody in the immune system.

a. the active site of an allosteric enzyme that binds to a specific substrate.

IP3 (inositol trisphosphate) is produced as a result of ___. a. the cleavage of a certain kind of phospholipid in the plasma membrane b. Ca2+ c. DAG d. protein kinase A activation e. phospholipase C

a. the cleavage of a certain kind of phospholipid in the plasma membrane

In liver cells, epinephrine stimulates the breakdown of glycogen. As the signal- transduction pathway progresses, _____ a. the signal is amplified b. the number of molecules involved remains constant c. the number of molecules involved decrease d. the signal is reduced e. glycogenesis is stimulated

a. the signal is amplified

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because _____. a. they amplify the original signal manyfold b. the number of molecules used is small and fixed c. the counter the harmful effects of phosphatases d. they are species specific e. they always lead to the same cellular response

a. they amplify the original signal manyfold

Gianna & Kylee Testosterone does not affect all cells of the body because ________ a. It is a local regulator b. Not all cells have cytoplasmic receptors for testosterone c. Testosterone cannot cross the plasma membrane d. It affects only cells that have ion channel receptors e. Not all cells in the body have membrane receptors for testosterone

b. Not all cells have cytoplasmic receptors for testosterone

In which of the following ways do plant hormones differ from hormones in animals? a. Plant hormones interact primarily with intracellular receptors. b. Plant hormones may travel in air or through vascular systems. c. Animal hormones are found in much greater concentration. d. Plant hormones are synthesized from two or more distinct molecules. e. Animal hormones are primarily for mating and embryonic development.

b. Plant hormones may travel in air or through vascular systems.

Protein phosphorylation is commonly involved with all of the following except a. activation of receptor tyrosine b. activation of G protein-coupled receptor c. activation of protein kinase molecules d. enzyme activation e. regulation of transcription by extracellular signaling molecules

b. activation of G protein-coupled receptor

Steroid hormones can enter a cell by simple diffusion. Therefore steroids ____. a. directly bind to DNA b. do not initiate cell signaling by interacting with a receptor in the plasma membrane c. do not bind to receptors d. act by phosphorylating DNA e. are not are example of signaling molecules

b. do not initiate cell signaling by interacting with a receptor in the plasma membrane

A difference between the mechanisms of cAMP and Ca2+ in signal transduction is that cAMP_____ and Ca2+ _____. a. is stored in the endoplasmic reticulum... is never stored in the cell b. is synthesized by an enzyme in response to a signal... is released from intracellular stores c. enters the cells via a transmembrane protein channel... enters the cell by diffusing across the plasma membrane d. is always present in the high levels in the cytosol... is present at low levels in the absence of a signal e. is tyrosine-kinase- receptor linked... is G-protein receptor linked

b. is synthesized by an enzyme in response to a signal... is released from intracellular stores

Why is apoptosis potentially threatening to the healthy "neighbors" of a dying cell? a. cell death would usually spread from one cell to the next vie paracrine signals. b. lysosomal enzymes exiting the dying cell would damage surrounding cells. c. Released cellular energy would interfere with the neighbors' energy budget d. Bits of membrane from the dying could merge with neighbors and bring in foreign receptors e. Neighbors cells would activate immunological responses.

b. lysosomal enzymes exiting the dying cell would damage surrounding cells.

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because a. they are species specific b. the amplify the original signal manyfold c. the number of molecules used is small and fixed d. they counter the harmful effects of the phosphatases e. they always lead to the same cellular response

b. the amplify the original signal manyfold

Protein phosphorylation is commonly involved with all of the following except a. Regulation of transcription by extracellular signiling molecules b. Enzyme activation c. Activation of G protein-coupled receptors d. Activation of receptor tyrosine kinases e. Activation of protein kinase molecules

c. Activation of G protein-coupled receptors

The receptor of tyrosine kinases is characterized by a. Channel protein shape and change b. Dimerization and IP3 bindinh c. Dimerization and phosphorylation d. A phosphorylation cascade e. GTP hydrolysis

c. Dimerization and phosphorylation

Apoptosis _________. a. Is only triggered by signals from outside the cell b. Occurs randomly during embryonic development of a nematode c. Is essential for the development of the nervous system d. Typically only involves a single signaling pathway e. All of the following responses are correct

c. Is essential for the development of the nervous system

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane? a. Intracellular receptor b. G protein- coupled receptor c. Ligand-gated ion channel d. Phosphorylated receptor tyrosine kinase dimer e. Receptor tyrosine kinase

c. Ligand-gated ion channel

Protein phosphorylation is commonly involved with all of the following except a. regulation of transcription by extracellular signaling molecules b. enzyme activation c. activation of G protein-coupled receptors d. activation of receptor tyrosine kinases e. activation of protein kinase molecules

c. activation of G protein-coupled receptors

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function? a. formation of mating complexes b. secretion of apoptotic signals c. aggregation of bacteria that can cause cavities d. secretion of substances that inhibit foreign bacteria e. digestion of unwanted parasite populations

c. aggregation of bacteria that can cause cavities

What are scaffolding proteins? a. ladderlike proteins that allow receptor-ligand complexes to climb through cells from one position to another b. microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores c. large molecules to which several relay proteins attach to facilitate cascade effects d. relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing e. proteins that can reach into the nucleus of a cell to affect transcription

c. large molecules to which several relay proteins attach to facilitate cascade effects

In the figure, the dots in the space between the two structures represent which of the following? a. receptor molecules b. signal transducers c. neurotransmitters d. hormones e. pheromones

c. neurotransmitters

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding? a. hormonal signaling b. autocrine signaling c. paracrine signaling d. endocrine signaling e. synaptic signaling

c. paracrine signaling

binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane? a. receptor tyrosine kinase b. G protein-coupled receptor c. phosphorylation receptor tyrosine kinase dimer d. ligand-gated ion channel e. intracellular receptor

c. phosphorylation receptor tyrosine kinase dimer

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because a. they are species specific b. they always lead to the same cellular response c. they amplify the original signal manyfold d. they counter the harmful effects of phosphatases e. the number of molecules used is small and fixed

c. they amplify the original signal manyfold

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because a. they are species specific b. they counter the harmful effects of phosphatases c. they amplify the original signal manyfold d. the number of molecules used is small and fixed e. they always lead to the same cellular response

c. they amplify the original signal manyfold***

The binding of a signal molecule to a ligand-gated ion channel _______ a. Results in the formation of ion channel dimers b. Alters the expression of genes, especially in neurons c. Promotes the binding of a steroid hormone to its receptor in the cytoplasm d. Affects the membrane potential e. causes the ion channel to phosphorylate an amino acid on a target molecule

d. Affects the membrane potential

Phosphorylation _____. a. Activates g-protein-linked receptors b. Is accomplished by protein phosphatase c. Always in actives a protein d. Can either activate or inactivate a protein e. Always activates a protein

d. Can either activate or inactivate a protein

The termination phase of cell signaling requires which of the following? a. removal of the receptor b. activation of a different set of relay molecules c. converting ATP to camp d. incompatibility of the binding of the signal molecule to the receptor e. apoptosis

d. incompatibility of the binding of the signal molecule to the receptor

2.) A small molecule that specifically binds to a larger molecule is called a _____. a. protein kinase b. competitive inhibitor c. DAG d. ligand e. alpha protein

d. ligand

A mutation in the active site of adenylyl cyclase that inactivates it would most likely lead to____ a. reduced binding of adenylyl cyclase to protein kinase A b. an increase in the amount of cAMP present in the cell c. increased binding of adenylyl cyclase to the G protein that activates it d. lower activity of protein kinase A e. higher activity of protein kinase A

d. lower activity of protein kinase A

Apoptosis involves which of the following? a. fragmentation of the DNA b. CELL-signaling pathways c. activation of cellular enzymes d. lysis of the cell e. digestion of cellular contents by scavenger cells

d. lysis of the cell

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this? a. G protein- coupled receptors b. ligand-gated ion channels c. steroid receptors d. receptor tyrosine kinases

d. receptor tyrosine kinases

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway? a. receptor b. relay molecule c. transducer d. signal molecule e. endocrine molecule

d. signal molecule

Which of the following types of signaling is represented by the figure? a. autocrine b. paracrine c. hormonal d. synaptic e. long distance

d. synaptic

The cellular response of a signal pathway that terminates at a transcription factor would be a. alteration of the cytoskeleton b. the activation of a metabolic pathway c. a change in the chemical composition of the cytosolic environment d. the synthesis of mRNA e. the activation of inactive enzyme

d. the synthesis of mRNA

A G protein is active when _____ a. GDP replaces GTP b. It is bound by its ligand and transported to the nucleus c. It is phosphorylated by protein kinase d. Ca2+ bi do to a G-Protein-linked receptor e. GTP is bound to it

e. GTP is bound to it

Steroid hormones can enter a cell by simple diffusion. Therefore steroids _____. a. move through a channel, down a gradient, and are nonpolar b. move up a concentration and are polar c. move down a concentration gradient and are polar d. move up a concentration gradient and are nonpolar e. None of the listed responses are correct

e. None of the listed responses are correct

Where do apoptotic signals come from? a. the nucleus only b. the ER only c. ligand binding only d. mitochondrial protein leakage only e. all of the above

e. all of the above

Phosphorylation ... a. is accomplished by protein phosphatases b. always activates a protein c. always inactivates a protein d. activates G-protein-linked receptors e. can either activate or inactivate a protein

e. can either activate or inactivate a protein

The activation of receptor tyrosine kinases is characterized by _____. a. channel protein shape and change b. dimerization and IP3 binding c. a phosphorylation cascade d. GTP hydrolysis e. dimerization and phosphorylation

e. dimerization and phosphorylation

What event would activate a G protein? a. hydrolysis of GDP to GTP b. hydrolysis of GTP to GDP c. phosphorylation of GDP to GTP d. phosphorylation of GtP to GDP e. replacement of GDP with GTP

e. replacement of GDP with GTP

Early work on signal transduction and glycogen metabolism by Sutherlnad indicated that _____. a. the signal molecule combined directly with a cytosolic enzyme to form an active quaternary structure. b. epinephrine is involved in response to stress c. the signal molecule worked equally well with intact or disrupted cells d. the cell signaling pathway involves two separate steps: transduction and response e. the signal molecule did not interact directly with the cytosolic enzyme, but required an intact plasma membrane before the enzyme could be activated

e. the signal molecule did not interact directly with the cytosolic enzyme, but required an intact plasma membrane before the enzyme could be activated