chapter nine: cell communication
What do we call proteins that act as a link between a receptor and proteins that initiate downstream signaling? a) Second messengers b) Interrupter proteins c) Adapter proteins d) Connector proteins
adapter proteins
The enzyme that produces cAMP from ATP is called ______ ______.
adenylyl cyclase
Why can steroid hormones cross the membrane and bind to intracellular receptors? a) Because they are non-polar b) Because they are polar molecules c) Because they are heteropolar molecules
because they are non-polar
What type of receptor proteins allow the diffusion of ions across cellular membranes? a) Kinases b) G proteins-coupled receptors c) Channel-linked receptors
channel-linked receptors
Hormones, which are involved in ______ signaling, last longer than signaling molecules involved in autocrine and paracrine signaling.
endocrine
Choose the four general types of cell communication? a) Nerve impulses b) Endocrine signaling c) Direct contact d) Paracrine signaling e) Signal transduction f) Synaptic signaling
endocrine signaling direct contact paracrine signaling synaptic signaling
The addition or removal of phosphate groups allow cells to control the function of ______.
proteins
which of the following receptor types is NOT a membrane receptor? a) channel-linked receptor b) enzymatic receptor c) G protein-coupled receptor d) steroid hormone receptors
steroid hormone receptors
Estrogen, cortisol, and progesterone are examples of which of the following? a) Steroids b) Kinases c) G proteins d) Second messengers
steroids
When the acetylcholine binds to the receptor sites a) a ligand is formed. b) the sodium channels open. c) the sodium channels remain closed. d) sodium ions diffuse through and enter the cell. e) sodium ions diffuse through and leave the cell.
the sodium channels open
Which of the following best summarizes the function of G proteins? a) They are the effector proteins in GPCRs. b) They deactivate GPCRs by hydrolyzing the bound GTP. c) They link GPCRs with effector proteins. d) They are second messengers.
they link gpcrs with effector proteins
What is the advantage to the cell of a signaling molecule entering directly into the cell, and binding to and activating a receptor that can induce transcription of DNA? a) A wide variety of responses can be elicited b) The signal can be greatly amplified within the cell c) The signal cascade can be more tightly regulated than when extracellular signaling molecules are used d) A change in gene expression can be quickly accomplished e) the signaling molecule itself is able to regulate gene expression
a change in gene expression can be quickly accomplished
Which of the following statements about the interaction between receptors and signaling pathways is true? a) GPCRs and RTKs cannot activate the same signaling pathway. b) GPCRs and RTKs are usually not found in the same cell. c) A GPCR and a RTK can activate the same signaling pathway.
a gpcr and a rtk can activate the same signaling pathway
You have identified a novel cytoplasmic protein. Through sequence analysis you are able to identify the presence of a number of serine/threonine phosphorylation motifs. Based on these data, you hypothesize that this protein may be a substrate for what kind of enzyme? a) A protein kinase b) A receptor tyrosine kinase c) A G protein-coupled receptor d) A tyrosine phosphatase e) A phospholipase
a protein kinase
Which of the following statements about signaling molecules and their action on different cells is true? a) A single signal will always have the same effect on a cell, regardless of the type of cell. b) A single signal may or may not have different effects on different cells. c) A single signal will always have a different effect on different types of cell.
a single signal may or may not have different effects on different cells
The second messenger cAMP is synthesized by the enzyme a) adenylyl cyclase. b) cAMP phoshodiesterase. c) ATPase. d) ligase. e) phosphorylase.
adenylyl cyclase
Identify the advantages and disadvantages of scaffold protein organization of kinase cascades: A physically arranged sequence is more efficient. a) advantages b) disadvantages
advantages
the same signal can have different effects in different cells because there... a) are different receptor subtypes that initiate different signal transduction pathways b) may be different coactivators in different cells c) may be different target proteins in different cells' signal transduction pathways d) all of the choices are correct
all of the choices are correct
How can epinephrine have different effects on different cells? a) Different cells have different receptors that bind epinephrine. b) Different cells activate different enzymes as a result of epinephrine binding. c) cAMP activates different kinases in different cells. d) All of these are TRUE.
all of these are true
How are animal and plant receptor kinases different? a) Animal receptor kinases are located in the cytoplasm, while plant receptor kinases are on the plasma membrane. b) Animal receptor kinases are membrane located, while those of plants are in the cytoplasm. c) Animals have serine/threonine receptor kinases, while plants have tyrosine receptor kinases. d) Animals have tyrosine receptor kinases, plant receptor kinases are serine/threonine kinases.
animals have tyrosine receptor kinases, plant receptor kinases are serine/threonine kinases
In ______ signaling, a cell sends a signal to itself, by secreting molecules that bind to receptors in its own plasma membrane.
autocrine
The protein Sonic Hedgehog (SHH) plays a role in specifying the identity of digits (such as fingers and toes) in mammals. Several digits arise directly from cells that both express and respond to secreted SHH. What type of signaling would this be considered? a) Direct contact b) Paracrine c) Endocrine d) Synaptic e) Autocrine
autocrine
Some cells send signals to themselves by secreting molecules that bind to receptors in their own plasma membranes. What is this known as? a) Endocrine signaling b) Autocrine signaling c) Synaptic signaling d) Self-signaling e) Paracrine signaling
autocrine signaling
The process of ______ occurs when two receptor-ligand complexes associate together and phosphorylate each other.
autophosphorylation
Steroid hormone receptors are usually inactive when the hormone that they bind is not present. Why? a) Because the gene transcription regulating domain is blocked by an inhibitor protein b) Because the DNA-binding domain has to bind the steroid hormone in order to recognize a DNA sequence c) Because the DNA-binding domain is blocked by an inhibitor protein
because the dna-binding domain is blocked by an inhibitor protein
Epinephrine binds to a) Alpha-adrenergic receptors on the cell membrane of liver cells. b) Alpha-adrenergic receptors in the cytoplasm of liver cells. c) Beta-adrenergic receptors on the cell membrane of liver cells. d) Beta-adrenergic receptors in the cytoplasm of liver cells. e) Beta-adrenergic receptors in the nucleus of liver cells.
beta-adrenergic receptors on the cell membrane of liver cells
Once inside of the cell, these lipid soluble hormones a) bind with a DNA molecule. b) bind with a specific receptor molecule inside the nucleus. c) bind with a mRNA molecule. d) bind with a specific receptor molecule inside the cytoplasm. e) bind with a ribosome.
bind with a specific receptor molecule inside the cytoplasm
in comparing small G proteins like ras and gpcr proteins, we can say that... a) both proteins have intrinsic GTPase activity that stops signaling b) both proteins are active bound to gtp c) ras is active bound to gdp and gpcrs are active bound to gtp d) both a and b are true
both a and b are true
Adenylyl cyclase is an effector protein that produces the second messenger ______.
camp
A series of protein kinases that phosphorylate each other in succession is called a kinase ______.
cascade
The sodium channel is formed by a channel protein. Which of the following statements about channel proteins is TRUE? a) Channel proteins cannot be regulated by the cell. b) Channel proteins couple the movement of a molecule to ATP hydrolysis, which provides energy for its active transport. c) Channel proteins can be opened or closed by cell signaling molecules. d) The same molecule that opens a channel protein will also be transported by the channel protein. e) Channel proteins are involved in both active and passive transport.
channel proteins can be opened or closed by cell signaling molecules
This type of receptor, once bound by ligand, can change conformation to allow specific substances to flow down their concentration gradient. This type of receptor is referred to as a ______.
channel-linked receptor
Which of the following are the three subclasses of membrane receptors? a) Channel-linked receptors b) Hormone receptors c) G protein-coupled receptors d) Neuroreceptors e) Enzymatic receptors
channel-linked receptors g protein-coupled receptors enzymatic receptors
Membrane receptors typically belong to one of three subclasses: ______-linked receptors, ______ receptors or G-______ coupled receptors.
channel; enzyme; protein
In synaptic signaling, neurotransmitters are released into a space that is referred to as a: a) chemical synapse. b) neuron junction. c) paracrine space. d) gap junction. e) plasmodesmata.
chemical synapse
Which of the following will typically have lower calcium levels? a) Cytoplasm b) Endoplasmic reticulum c) Extracellular space
cytoplasm
Intracellular receptors are usually located in the ______ or in the ______.
cytoplasm; nucleus
Prior to binding the hormone, steroid hormone receptors are located in the ______, however, their primary site of action is the ______.
cytoplasm; nucleus
The action of PKA phosphorylating glycogen synthase leads to which of the following? a) Increased expression of genes encoding enzymes involved in glucose synthesis b) Increased glycogen synthesis c) Decreased glycogen synthesis d) Decreased expression of genes encoding enzymes involved in glucose synthesis
decreased glycogen synthesis
The two basic mechanisms that can inactivate RTK's are which of the following? a) Dephosphorylation b) Internalization c) Phosphorylation d) Externalization
dephosphorylation internalization
Lipid soluble hormones a) require a membrane receptor protein to enter the cell. b) diffuse through the cell membrane. c) enter the cell through active transport. d) work as ligands on the surface of the cell membrane. e) require specific gates to pass through the cell membrane.
diffuse through the cell membrane
One cell sends second messengers to another cell through gap junctions. What type of signaling would this be considered? a) Direct contact b) Paracrine c) Endocrine d) Synaptic e) Autocrine
direct contact
The type of cell communication characterized by the interaction of a signal molecule in the plasma membrane of one cell and a receptor protein in the plasma membrane of an adjacent cell is called which of the following? a) Membrane contact b) Indirect contact c) Contact-dependent communication d) Direct contact
direct contact
Identify the advantages and disadvantages of scaffold protein organization of kinase cascades: Reduces the amplification effect of the kinase cascade. a) advantages b) disadvantages
disadvantages
Each steroid receptor has three functional domains--1. a hormone-binding domain, 2. A ______-binding domain, and 3. a domain that can interact with co-activators to affect the level of gene ______.
dna; expression
Addison's disease is a disorder that results from a reduction in production of glucocorticoids and mineralocorticoids. Individuals with Addison's disease suffer from a variety of systemic symptoms including: muscle weakness, fever, issues with the gastrointestinal tract, and increased tanning. Considering this information, what type of signaling do you think that glucocorticoids and mineralocorticoids stimulate? a) Direct contact b) Paracrine c) Endocrine d) Synaptic e) Autocrine
endocrine
Epinephrine is produced by the central nervous system and has an effect throughout the body, such as in the heart, liver, and blood vessels. Epinephrine is part of what kind of signaling? a) autocrine signaling b) paracrine signaling c) endocrine signaling d) Direct intercellular signaling e) Contact-dependent signaling
endocrine signaling
Growth of new blood vessels is stimulated by vascular endothelial growth factor (VEGF). This ligand binds to the VEGF receptor, which leads to the dimerization and autophosphorylation of this receptor on cytoplasmic tyrosines. What type of receptor is the VEGF receptor? a) Channel-linked receptor b) Enzymatic receptor c) G protein-coupled receptor d) Steroid hormone receptor
enzymatic receptor
This type of receptor is a transmembrane receptor. It has an extracellular domain that binds to ligand, and an intracellular domain that can directly phosphorylate other proteins. This is an example of an ______.
enzymatic receptor
Examples of steroids include which of the following? a) cAMP b) Estrogen c) Testosterone d) Cortisol e) Kinases
estrogen testosterone cortisol
Intracellular receptors usually act by changing gene ______ in the cell.
expression
True or False. A signal transduction module can only be activated by a specific type of receptor.
false. different receptors can activate the same pathway.
What are the five groups in the GPCR family? a) Frizzled/Taste 2 b) Secretin c) Smell d) Glutamate e) Adhesion f) Vision g) Rhodopsin
frizzled/taste 2 secretin glutamate adhesion rhodopsin
The binding of epinephrine to its receptor activates a a) A protein. b) D protein. c) G protein. d) K protein. e) M protein.
g protein
This type of receptor is not an enzyme itself, but is bound to an enzyme that can hydrolyze GTP to GDP. This type of receptor is referred to as a ______.
g protein-coupled receptor
The cell surface receptors that can act only indirectly on plasma membrane-bound enzymes or ion channels are called: a) G protein-coupled receptors. b) gated ion channels. c) enzymatic receptors. d) second messenger receptors.
g protein-coupled receptors
Which of the three types of membrane receptors acts indirectly via a "helper" molecule? a) G protein-coupled receptors b) Enzymatic receptors c) Channel-linked receptors
g protein-coupled receptors
How are G protein-coupled receptors different from enzymatic receptors? a) G-protein coupled receptors transport their signal inside the cell. b) G protein-coupled receptors act indirectly with the help of an assisting protein. c) G protein-coupled proteins usually bind hydrophobic signals.
g protein-coupled receptors act indirectly with the help of an assisting protein
What proteins can bind GTP and GDP? a) Chemically-gated ion channels b) Enzymatic receptors c) G-protein-coupled receptors d) G proteins
g proteins
The binding of epinephrine to its receptor activates ______ which in turn activates ______. a) protein kinase A; G protein b) protein kinase A; adenylyl cyclase c) adenylyl cyclase; G-protein d) G-protein; adenylyl cyclase e) G-protein; protein kinase A
g-protein; adenylyl cyclase
Two hormones that can stimulate liver cells to mobilize glucose are a) glucagon b) glyconase c) epinephrine d) gluconase
glucagon epinephrine
The enzyme phosphorylase catalyzes the conversion of a) glycogen into glucose-6-phosphate. b) glycogen into glucose. c) glucose into glycogen. d) glucose into glucose-6-phosphate. e) glucose-6-phosphate into glycogen.
glycogen into glucose-6-phosphate
G proteins are so named because of their ability to bind which of the following? a) GTP and GPCR b) GDP to GPCR c) GDP but not GTP d) GTP and GDP
gtp and gdp
The three functional domains of the steroid receptors can be described as which of the following? a) Hormone-binding domain b) DNA-binding domain c) Domain that affects the level of gene transcription d) RNA-binding domain
hormone-binding domain dna-binding domain domain that affects the level of gene transcription
Which of the following statements that compare endocrine, paracrine and autocrine signaling is true? a) Hormones are longer lived than paracrine or autocrine signals. b) Hormones are shorter lived than either paracrine or autocrine signals. c) Hormones are shorter lived than paracrine signals. d) Hormones are as long lived as paracrine signals.
hormones are longer lived than paracrine or autocrine signals
Cell surface or membrane receptors bind this type of ligand. a) Hydrophobic b) Hydrophilic c) Both hydrophobic and hydrophilic
hydrophilic
Intracellular receptors bind this type of ligand. a) Hydrophobic b) Hydrophilic c) Both hydrophobic and hydrophilic
hydrophobic
signal transduction pathways... a) are necessary for signals to cross the membrane b) include the intracellular events stimulated by an extracellular signal c) include the extracellular events stimulated by an intracellular signal d) are only found in cases where the signal can cross the membrane
include the intracellular events stimulated by an extracellular signal
When a steroid hormone binds the hormone-binding domain of a steroid hormone receptor, the receptor's conformation changes. As a result of this, the ______ protein is released, which exposes the ______-binding site of the receptor.
inhibitor; dna
Where do second messengers relay signals? a) Outside the cell b) Inside the cell c) To the cell surface receptor
inside the cell
Dephosphorylation and ______ are the two basic mechanisms that can inactivate receptor tyrosine kinases.
internalization
This type of receptor binds to hydrophobic ligands. This type of receptor is referred to as an ______.
intracellular receptor
Channel-linked receptors are proteins that allow the diffusion of ______ across cellular membranes.
ions
How are the two second messengers IP3 and Ca2+ related inside the cell? a) IP3 inhibits receptors on the ER from releasing Ca2+. b) IP3 and Ca2+ are not in the same pathway. c) IP3 activates receptors in the plasma membrane which act as Ca2+ channels. d) IP3 activates receptors on the ER which act as Ca2+ channels.
ip3 activates receptors on the er which act as ca2+ channels
Which of the following statements about cAMP is FALSE? a) It activates the same signal cascade in many different cell types. b) It is produced by the action of adenylyl cyclase in many different cell types. c) It is synthesized from ATP. d) It acts as a second messenger in many different cell types.
it activates the same signal cascade in many different cell types
Which of the following describes a single signaling molecule? a) It can only affect a single type of cell. b) It always have the same effect, regardless of the cell it acts on. c) It can have different effects in different cells.
it can have different effects in different cells
When PKA phosphorylates glycogen synthase, what happens to the function of this enzyme? a) It is activated. b) It is inhibited. c) It is reversed.
it is inhibited
Which of the following characters is NOT a reason that cAMP is considered a second messenger? a) it is made from ATP b) it is produced in response to a cellular signal binding a receptor c) it can quickly diffuse through the cell d) All of these make cAMP a second messenger
it is made from atp
Which of the following statements about inositol triphosphate is FALSE? a) It is formed in the cytoplasm. b) It is synthesized by a membrane-bound enzyme. c) It is synthesized by the enzyme phosphatase. d) It binds to and opens Ca2+ channels in the endoplasmic reticulum. e) All of these choices are correct
it is synthesized by the enzyme phosphatase
what is the function of ras during tyrosine kinase cell signaling? a) it activates the opening of channel-linked receptors b) it is an enzyme that synthesizes second messengers c) it links the receptor protein to the MAP kinase pathway d) it phosphorylates other enzymes as part of a pathway
it links the receptor protein to the MAP kinase pathway
Nicotine is a molecule that is chemically similar to acetylcholine and binds to the same receptors. What affect will nicotine have on the cell shown in the animation? a) it will open sodium channels b) It will close sodium channels c) It will kill the cell d) It will excite the cell e) It will depress the cell
it will open sodium channels
A series of protein kinases that phosphorylate each other in succession is called a a) receptor tyrosine kinase. b) a MAP kinase. c) kinase cascade.
kinase cascade
signaling through receptor tyrosine kinases often... a) leads to the production of the second messenger cAMP b) leads to the production of the second messenger IP3 c) stimulates gene expression directly d) leads to the activation of a cascade of kinase enzymes
leads to the activation of a cascade of kinase enzymes
A signaling molecule is known as which of the following? a) Protein b) Ligand c) Intercellular protein d) Ligase
ligand
What term is used to describe a signaling molecule? a) Ligand b) Substrate c) Receptor d) Effector
ligand
What enzyme phosphorylates MAP kinase kinase? a) MAP kinase b) MAP kinase kinase c) MAP kinase kinase kinase d) MAP phosphatase
map kinase kinase kinase
These molecules can directly convert extracellular signals into intracellular signals. a) Second messengers b) Scaffolds c) Membrane receptors d) Adapter proteins e) G proteins
membrane receptors
Small molecules or ions that relay signals inside the cytoplasm are called second ______.
messengers
Signaling molecules that stimulate a cell to divide are called which of the following? a) Mutagens b) Kinases c) Nitric oxide d) Mitogens
mitogens
A process in which one molecule fits specifically based on its complementary shape with another molecule is called which of the following? a) Signal transduction b) Molecular complementarity c) Molecular recognition
molecular recognition
the ion Ca2+ can act as a second messenger because it is... a) produced by the enzyme calcium synthase b) normally at a high level in the cytoplasm c) normally at a low level in the cytoplasm d) stored in the cytoplasm
normally at a low level in the cytoplasm
Leptin is a circulating hormone that is produced by fat cells and plays a role in body metabolism and obesity. It normally binds to receptors in the brain and inhibits appetite. Studies have demonstrated that when obese mice that are leptin deficient are injected with leptin they quickly lose their excess weight. Interestingly, however, many overweight people have high levels of leptin in their bloodstream. Why do you think that the high levels of leptin in obese individuals are insufficient to curb their appetite? a) Paracrine signaling may be disrupted in obese people with high levels of leptin. b) Obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity. c) The form of leptin released by obese people may lack protein kinase activity. d) In obese people with high levels of leptin, the leptin is a non-functional second messenger.
obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity
In response to injury, cell fragments called platelets get activated to induce clotting. Activated platelets release factors that can in turn bind to specific membrane receptors on nearby cells. What type of signaling would this be considered? a) Direct contact b) Paracrine c) Endocrine d) Synaptic e) Autocrine
paracrine
In what type of signaling do secretions from one cell have an effect only on the cells in the neighboring area? a) Direct intercellular b) Paracrine c) Autocrine d) Endocrine
paracrine
A researcher is working to generate a new cancer drug. Thus far, he has identified a compound that can reduce the size of tumors in the lung. However, in order for the drug to work, the lung tumor has to be small. In addition, the tumor cannot have metastasized (spread to other areas of the body). Furthermore, he knows that the drug acts to prohibit the signaling from one tumor cell to another tumor cell. Given the above information, this new drug prohibits: a) synaptic signaling between tumor cells. b) autocrine signaling between tumor cells. c) paracrine signaling between tumor cells. d) endocrine signaling between tumor cells.
paracrine signaling between tumor cells
The four kinds of cell communication (between two different cells) based on the distance from source to receptor are: direct contact, ______ signaling, ______ signaling, and ______ signaling.
paracrine; synaptic; endocrine
the receptors for steroid hormones and peptide hormones are fundamentally different because... a) of the great difference in size of the molecule b) peptides are one of the four major polymers and steroids are simple ringed structures c) peptides are hydrophilic and steroids are hydrophobic d) peptides are hydrophobic and steroids are hydrophilic
peptides are hydrophilic and steroids are hydrophobic
The addition or removal of which group is a major source of control for protein function during signal transduction? a) Phosphate b) Acetyl c) Carboxyl
phosphate
The enzyme alpha-kinase adds ______ to proteins. a) acetates b) benzoats c) carbonates d) phosphates e) hydroxyls
phosphates
the function of a ______ is to add phosphates to proteins, whereas a ______ functions to remove the phosphates. a) tyrosine; serine b) protein phosphatase; protein dephosphatase c) protein kinase; protein phosphatase d) receptor; ligand
protein kinase; protein phosphatase
The small GTP-binding protein that links the RTK with the MAP kinase cascade is known as which of the following? a) Ras protein b) Initial kinase protein c) Master kinase protein d) G protein
ras protein
Which is the active form of the Ras protein? a) Ras b) Ras-P c) Ras-GTP d) Ras-GDP
ras-gtp
Adapter proteins bind to phosphotyrosines and act as a link between a ______ and proteins that initiate downstream signaling.
receptor
Which of the following statements about receptors is true? a) Receptors can have several subtypes/isoforms in the same organism. b) An organism can only have one form of any given receptor. c) Some receptors can bind several ligand subtypes/isoforms.
receptors can have several subtypes/isoforms in the same organism
The interaction of a receptor with its ligand is an example of molecular ______.
recognition
What function does the relay protein Ras have in the signal transduction pathway? a) Relay cellular signals to activate EGF receptors b) Relay cellular signals to proteins that form the protein kinase cascade c) Relay cellular signals to activate transcription factors
relay cellular signals to proteins that form the protein kinase cascade
The alpha subunit of the G-protein is activated by a) separating from the gamma and beta subunits. b) the G-protein becoming phosphorylated c) binding to the calcium ions. d) replacing the GDP with GTP. e) replacing the GTP with GDP.
replacing the gdp with gtp
Large proteins that organize the components of a kinase cascade into a single protein complex are known as which of the following? a) G proteins b) Ras proteins c) Scaffold proteins
scaffold proteins
Some enzymatic receptors and most G protein-coupled receptors transmit the signal into the cytoplasm by utilizing other substances within the cytoplasm that are referred to as: a) genes. b) intracellular receptors. c) second messengers. d) first messengers.
second messengers
paracrine signaling is characterized by ligands that are... a) produced by the cell itself b) secreted by neighboring cells c) present on the plasma membrane of neighboring cells d) secreted by distant cells
secreted by neighboring cells
G protein-coupled receptors are the largest family of cell surface receptors. Each receptor passes through the plasma membrane how many times? a) Once b) Three times c) Five times d) Seven times
seven times
What effects do paracrine signals have? a) Short, distant effects b) Long, local effects c) Short, local effects d) Long, distant effects
short, local effects
Paracrine signals typically have ______-lived, ______ effects.
short; local
A small number of cell surface receptors can ultimately generate a large intracellular response due to activation of kinase cascades. This is referred to as: a) signal amplification. b) signal transduction. c) signal dampening. d) signal activation.
signal amplification
Different cells can respond to the same signaling molecule in a completely (sometimes opposite) different way because they can have different _____ ______ pathways associated with that signaling molecule.
signal transduction
different receptors can have the same effect on a cell. one reason for this is that... a) most receptors produce the same second messenger b) different isoforms of receptors bind different ligands, but stimulate the same signaling pathway c) signal transduction pathways intersect - the same pathway can be stimulated by different receptors d) all receptors converge on the same signal transduction pathways
signal transduction pathways intersect - the same pathway can be stimulated by different receptors
which of the following best describes the immediate effect of ligand binding to a G protein-coupling receptor? a) the G protein trimer releases a gdp and binds a gtp b) the G protein trimer dissociates from the receptor c) the G protein trimer interacts with an effector protein d) the a subunit of the G protein becomes phosphorylated
the G protein trimer releases a gdp and binds a gtp
Why are phosphorylation and dephosphorylation reactions commonly used to regulate signal transduction pathways? a) Phosphate groups are efficient second messengers b) Protein kinases and phosphatases are abundant in most cells c) The hydrolysis of bound GTP generates GDP, which can change the activity of proteins bound to GDP d) The addition or removal of a phosphate group can expose or hide potential binding sites in proteins or change protein activity
the addition or removal of a phosphate group can expose or hide potential binding sites in proteins or change protein activity
Which of the following describes the response of skeletal muscle cells to an outflow of Ca2+ from the ER? a) The cells respond by converting glucose into glycogen. b) The cells respond by secreting the Ca2+ outside the cell. c) The cells respond by secreting a hormone. d) The cells respond by contracting.
the cells respond by contracting
A mutation that affects Ca++ binding to calmodulin is most likely to interfere with what aspect of a signal transduction pathway? a) The flow of Ca++ ions through ion channel receptors b) The cellular response to the second messenger c) The MAP kinase cascade d) G protein activity
the cellular response to the second messenger
Using a specific chemical, a cell biologist has blocked one type of channel-linked receptor in a lab rat's liver tissue. What was the likely mechanism of the chemical she used? a) The chemical prohibits binding of a ligand to the receptor. b) The chemical prohibits ions from entering the cell via active transport. c) The chemical causes ions to move in the opposite direction of the ion gradient. d) The chemical prohibits second messenger signaling.
the chemical prohibits binding of a ligand to the receptor
You are planning to perform some protein-protein interaction studies to identify a receptor for a steroid hormone you have been working on. You start by fractionating the cell. What cell fraction would you want to work with to identify the steroid hormone receptor of interest? a) The plasma membrane fraction b) The extracellular fraction c) The cytoplasmic fraction d) The mitochondrial fraction e) The ribosomal fraction
the cytoplasmic fraction
how does the function of an intracellular receptor differ from that of a membrane receptor? a) the intracellular receptor binds a ligand b) the intracellular receptor binds dna c) the intracellular receptor activates a kinase d) the intracellular receptor functions as a second messenger
the intracellular receptor binds dna
Why is it possible for Na+ to enter the cell when the channel is open? a) ATP is used to provide energy to pump Na+ b) It is co-transported with a molecule that is moving down its gradient c) Na+ are only capable of moving inside the cell d) The Na+/K+ pump previously built a high concentration of Na+ on the outside of the cell, so Na+ is diffusing e) Na+ first moves out of the cell across the lipid bilayer by simple diffusion, and then enters the cell by facilitated diffusion
the na+/k+ pump previously built a high concentration of na+ on the outside of the cell, so na+ is diffusing
A mutation in the G-protein, decreasing its ability to hydrolyze its bound GTP, will have what effect on the cell signaling pathway in which it is involved? a) the pathway will be under expressed b) the pathway will be over expressed c) the pathway will be expressed, even in the absence of a signal d) the pathway will be activated by other receptors, such as receptor tyrosine kinases e) The cell will cease to activate the G-protein linked receptor
the pathway will be over expressed
A mutation that alters the G-protein's affinity for GDP, making it less likely to release GDP even when stimulated by a receptor, will have what effect on the cell signaling pathway in which it is involved? a) the pathway will be under expressed b) the pathway will be over expressed c) the pathway will be expressed, even in the absence of a signal d) the pathway will be activated by other receptors, such as receptor tyrosine kinases e) The cell will cease to activate the G-protein linked receptor
the pathway will be under expressed
A cell has a mutation resulting in the aldosterone receptor being unable to efficiently bind to DNA. What effect will this have on the cell? a) Aldosterone cannot be released in the blood as a signaling molecule. b) Aldosterone will not be able to bind to its receptor in the cytoplasm, so the signaling pathway will not elicit its response. c) The receptor will become active, but once inside the nucleus it will not be able to initiate transcription, so the signaling pathway will not elicit its response. d) mRNA will be transcribed, but protein translation will not occur properly, so the signaling pathway will not elicit its response.
the receptor will become active, but once inside the nucleus it will not be able to initiate transcription, so the signaling pathway will not elicit its response
When the acetylcholine receptor sites are not occupied a) a ligand is formed. b) the sodium channels open. c) the sodium channels remain closed. d) sodium ions diffuse through and enter the cell. e) sodium ions diffuse through and leave the cell.
the sodium channels remain closed
What property defines most ligands for intracellular receptors? a) They are lipid-soluble b) They are hydrophilic c) They are molecules that can perform significant hydrogen bonding interactions with water d) They are large molecules
they are lipid-soluble
Epinephrine and glucagon can both act on liver cells producing the same response. How do these two hormones differ with respect to liver cells? a) Epinephrine binds to a receptor tyrosine kinase, while glucagon binds a GPCR. b) Epinephrine activates adenylyl cyclase, glucagon activates guanylyl cyclase. c) They bind to different receptors, however, both receptors are GPCRs.
they bind to different receptors, however, both receptors are gpcrs
Which of the following are ways in which intracellular receptors can act? a) They can act by producing changes in gene expression. b) They can act by opening ion channels in the membrane. c) They can be enzymatic receptors that modify molecules in the cytoplasm. d) They can act by activating G proteins.
they can act by producing changes in gene expression they can be enzymatic receptors that modify molecules in the cytoplasm
What is the function of a protein kinase? a) To remove phosphate groups from proteins b) To cleave membrane phospholipids c) To phosphorylate GDP to generate GTP d) To add phosphate groups onto proteins
to add phosphate groups onto proteins
A signal ______ pathway is initiated when a ligand binds to a receptor protein.
transduction
True or False. Some receptors can have several different subtypes or isoforms.
true
True or False. The combination of the calcium and the calmodulin produces the response of the cell to the ligand.
true
True or False. The sodium channels in the cell membrane have receptor sites for acetylcholine.
true
the action of steroid hormones is often longer-lived than that of peptide hormones. this is because they... a) enter the cell and act like enzymes for a longer period of time b) turn on gene expression to produce proteins that persist in the cell c) result in the production of second messengers that act directly on cellular processes d) stimulate G proteins that act directly on cellular processes
turn on gene expression to produce proteins that persist in the cell
Which of the following statements regarding signal transduction pathways (abbreviated SDP below) and the response of different cells to the same signal is true? a) Every signaling molecule is associated with a unique receptor and SDP. b) A signal is always associated with one unique SDP, but different cells can have different receptors for the signal and respond differently to it. c) Two different cells can have different SDPs which allows them to respond differently to the same signaling molecule.
two different cells can have different sdps which allows them to respond differently to the same signaling molecule
Autophosphorylation occurs when which of the following occurs? a) Two receptor-ligand complexes associate and phosphorylate each other b) A protein kinase phosphorylates tyrosines c) Two cells associate and phosphorylate each other
two receptor-ligand complexes associate and phosphorylate each other
In animals, receptor kinases are usually ______ kinases; in contrast, plant receptors kinases belong to the ______-threonine type.
tyrosine; serine
