bio 6 chapter 11

sutherland discovered that the signaling molecule epinephrine is responsible for which of the following events?

elevating cytosolic concentrations of cyclic AMP

which of the following is the most plausible explanation for why an animal cell would be unable to reduce the calcium concentration in tis cytosol compared with the extracellular fluid?

insufficient ATP levels in the cytosol

what is a primary function of transcription factors?

they control gene expression

what role fo phosphatases play in signal transduction pathways?

they inactivate protein kinases to turn off signal transduction

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound that does which of the following?

- blocks G protein activity in liver cells - increase phosphodiesterase activity in liver cells

Put the steps of the process of signal transduction in the order they occur: 1. A conformational change in the signal-receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released.

3, 1, 5, 2, 4

Why has C. elegans proven to be a useful model for understanding apoptosis?

C. elegans undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development

which of the following is a correct association?

GTPase activity and hydrolysis of GTP to GDP

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result?

a form of cancer in which there is insufficient apoptosis

which of the following statements about a g protein signaling pathway is true?

a g protein bound to gtp is in its active state

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?

a lipid-soluble signal

protein kinase is an enzyme that functions in which of the following ways?

activates or inactivates other proteins by adding a phosphate group to them

protein phosphorylation is commonly involved with all of the following except

activation of G-protein coupled receptors

which of the following processes generally requires protein phosphorylation?

activation of receptor tyrosine kinases

which of the following is true during a typical cAMP-mediated signal transduction event?

adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

aggregation of bacteria that can cause cavities

phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they _____________.

amplify the original signal many times

many g protein-coupled receptors contain seven transmembrane (alpha)-helical domains. the amino end of the protein lies at the exterior of the plasma membrane. loops of amino acids connect the helices either at the exterior surface or on the cytosolic surface of the membrane. the loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others. where would you expect to find the carboxyl end of the protein?

at the cytosolic surface

many g protein-coupled receptors contain seven transmembrane (alpha)-helical domains. the amino end of the protein lies at the exterior of the plasma membrane. loops of amino acids connect the helices either at the exterior surface or on the cytosolic surface of the membrane. the loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others. where would a g protein most likely interact with this receptor?

at the loop between h5 and h6

In yeast signal transduction, a yeast cell releases a mating factor which _____.

binds to receptors on the membranes of other types of yeast cells

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of which of the following molecules?

cAMP

Consider this pathway: epinephrine --> G protein-coupled receptor --> G protein --> adenylyl cyclase --> cAMP. the second messenger in this pathway is ______________.

cAMP

a signal transmitted via phosphorylation of a series of proteins is generally associated with which of the following events?

conformational changes to each protein in the series

the activation of receptor tyrosine kinases is characterized by

dimerization and phosphorylation

cells that are infected, damaged, or have reached the end of their functional life span often undergo "programmed cell death." this controlled cell suicide is called apoptosis. select the appropriate description of this event on the cell's life cycle.

during apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

estrogen binds to specific receptors inside many kinds of cells, each with different responses

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

glycogen breakdown was observed only when epinephrine was administered to intact cells

which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

glycogen breakdown was observed only when epinephrine was administered to intact cells.

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following, if found in cells or organisms as they age, would provide evidence that this is related to cell signaling?

growth factor ligands do not bind as efficiently to receptors

viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. viagra acts by inhibiting which of the following events?

hydrolysis of cGMP to GMP

particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels on various cancer cells. HER2 is an RTK that is present at excessively high levels in some breast cancer cells. herceptin is a protein that binds to HER2 and inhibits cell division. herceptin may be an effective treatment for breast cancer treatment under which of the following conditions?

if the patient's cancer cell have excessive levels of HER2

scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testes. for this to happen, there must be direct communication between the extracellular matrix and the developing cells. which kind of transmembrane protein would most likely be involved in this kind of induction?

integrins

Why does testosterone, a lipid-soluble signaling molecule that crosses the membranes of all cells, affect only target cells?

intracellular receptors for testosterone are present only in target cells

what is the most likely mechanism by which testosterone functions inside a cell?

it binds with a receptor protein that enters the nucleus and activates expression of specific genes.

how does the toxin of vibrio cholerae cause profuse diarrhea?

it modifies a g protein involved in regulating salt and water secretion

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

it prevents the caspase activity of ced-3 and ced-4

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

it would not be able to activate g proteins on the cytoplasmic side of the plasma membrane

what are scaffolding proteins?

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

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?

ligand-gated ion channel

apoptosis involves which of the following?

lysis of the cell

use the following figure to answer the question. in the figure, the dots in the space between the structures represent which of the following?

neurotransmitters

in which of the following ways do plant hormones differ from hormones in animals?

plant hormones frequently travel through the air as a gas

which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?

paracrine signaling

the activity of adenylyl cyclase is essentially the opposite of which of the following enzymes?

phosphodiesterase

an inhibitor of which of the following enzymes could be used to block the release of calcium from the endoplasmic reticulum?

phospholipase C

which of the following statements is true of signal molecules?

protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors

which of the following results would most likely be an immediate result of a growth factor binding to its receptor?

protein kinase activity

which of the following activities would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins

receptor tyrosine kinase activity

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?

receptor tyrosine kinases

which of the following amino acids are most frequent phosphorylated by protein kinases in the cytoplasm during signal transduction?

serine and threonine

when a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

signal molecule

which of the following provides the best evidence that cell-signaling pathways evolved early in the history of life?

signal transduction molecules identified in distantly related organisms are similar

the receptors for steroid hormones are located inside the cell instead of the membrane surface like most other signal receptors. how do steroids gain access to their receptors?

steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane

use the following figure to answer the question. which of the following types of signaling is represented in the figure?

synaptic

a mutation that knows out the GTPase activity of a G protein would have what effect on a cell?

the G protein would always be active

which of the following statements describes the events of apoptosis?

the cell's DNA and organelles become fragmented, the cell dies, and it is phagocytized

what does it mean to say that a signal is transduced?

the physical form of the signal changes as it passes from the cell membrane to the ultimate intracellular target

which of the following statements is true of steroid receptors

the receptor may be inside the nucleus of a target cell

hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. which of the following conditions is required for the target organ to respond to a particular hormone?

the target organ must have receptors that recognize and bind the hormone molecule.

which of the following statements describes a likely effect of a drug designed that inhibits the cellular response to testosterone?

the transcription of certain genes would decrease

yeast cells of mating type a are genetically engineered to produce only mating fact (alpha) instead of the normal mating factor a. the gene for the mating factor receptor was unaltered. how will these engineered cells behave in terms of mating?

they will mate with each other or with normal mating type a cells, but not with normal mating type (alpha) cells.