Exam 2

Question 1

The function of endosomes?
a Sort endocytosed materials
b Secretion of neurosecretory hormones
c oxidative breakdown of toxic materials

Answer 1

a Sort endocytosed material

Question 2

Which of the following statements about the endoplasmic reticulum (ER) is
FALSE?
a The ER membrane is contiguous with the outer nuclear membrane.
b The ER is the major site for new membrane synthesis in the cell.
c Proteins to be delivered to the ER lumen are synthesized on the smooth ER.
d Steroid hormones are synthesized on the smooth ER.

Answer 2

c Proteins to be delivered to the ER lumen are synthesized on the smooth ER.

Question 3

A key function of the Golgi apparatus is:
a modification, sorting, and packaging of proteins and lipids for either secretion or delivery to
another organelle
b translation of membrane-bound and secreted proteins
c oxidative breakdown of toxic molecules
d intracellular degradation

Answer 3

a modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle

Question 4

(Q023) Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels?
a Golgi → lysosome → plasma membrane
b ER → Golgi → plasma membrane
c ER → lysosome → plasma membrane
d lysosome → endosome → plasma membrane

Answer 4

b ER → Golgi → plasma membrane

Question 5

Q039) Which of the following is NOT a process that delivers material to the
lysosome?
a transcytosis
b pinocytosis
c phagocytosis
d autophagy

Answer 5

a transcytosis

Question 6

(Q020) Which of the following statements about a protein in the lumen of the ER is FALSE?
a A protein in the lumen of the ER is synthesized by ribosomes on the ER membrane.
b Some of the proteins in the lumen of the ER can end up in the lumen of an organelle in the endomembrane system.
c Some of the proteins in the lumen of the ER can end up in the plasma membrane.
d Some of the proteins in the lumen of the ER can end up in the extracellular space.

Answer 6

c Some of the proteins in the lumen of the ER can end up in the plasma membrane.

Question 7

(Q006) Proteins that are fully translated in the cytosol do not end up in
a the mitochondria.
b the interior of the nucleus.
c transport vesicles.
d the cytosol.

Answer 7

c transport vesicles

Question 8

(Q021) Which of the following statements is TRUE?
a Proteins destined for the ER are translated by a special pool of ribosomes whose subunits are always associated with the outer ER membrane.
b Proteins destined for the ER are translated by a pool of cytosolic ribosomes that contain ER-targeting sequences that interact with ER-associated protein translocators.
c Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation.
d Proteins destined for the ER translocate their associated mRNAs into the ER lumen where they are translated.

Answer 8

c Proteins destined for the ER are translated by cytosolic ribosomes and are
targeted to the ER when a signal sequence emerges during translation.

Question 9

Predict the membrane orientation of a protein that is synthesized with an uncleaved,
internal signal sequence (as below in red) but did not contain a stop-transfer
sequence (shown in yellow below)?
a Amino terminus in the ER lumen and carboxy terminus in the cytosol
b Both N- and C-termini in the cytosol
c Both N- and C-termini in the ER lumen
d Amino terminus in the cytosol and carboxy terminus in the ER lumen

Answer 9

d Amino terminus in the cytosol and carboxy terminus in the ER lumen

Question 10

(Q011) A large protein that passes through the nuclear pore must have an appropriate
a. sorting sequence, which typically contains the positively charged amino acids lysine and arginine.
b sequence to interact with the nuclear fibrils.
c Ran-interacting protein domain.
d sorting sequence, which typically contains the hydrophobic amino acids leucine
and isoleucine.

Answer 10

a. sorting sequence, which typically contains the positively charged amino acids lysine and arginine.

Question 11

(Q010) Which of the following statements about nuclear transport is TRUE?
a Nuclear pores are made up of many copies of a single protein.
b Nuclear import receptors bind to proteins in the cytosol and bring the proteins to
the nuclear pores, where the proteins are released from the receptors into the
pores for transit into the nucleus.
c mRNAs and proteins transit the nucleus through different types of nuclear pores.
d Nuclear pores contain proteins with disordered segments that fill the channel and allow small water-soluble molecules to pass through in a non-selective fashion

Answer 11

d Nuclear pores contain proteins with disordered segments that fill the channel and allow small water-soluble molecules to pass through in a non-selective fashion

Question 12

(Q014) Which of the following statements about transport into mitochondria and chloroplasts is FALSE?
a The signal sequence on proteins destined for these organelles is recognized by a receptor protein in the outer membrane of these organelles.
b Proteins that are transported into these organelles are unfolded as they are being transported.
c After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane.
d Signal peptidase will remove the signal sequence once the protein has been imported into these organelles

Answer 12

c After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane.

Question 13

All of the following are true about clathrin-coated vesicles EXCEPT:
a Receptor-mediated endocytosis often occurs via clathrin-coated vesicles
b Specificity of cargo is determined by clathrin binding
c As cargo/cargo receptor/adaptin/clathrin complexes come together, clathrin interactions bend the membrane into what is called a “coated pit”
d A protein called dynamin is necessary to pinch off the vesicle from the membrane

Answer 13

b Specificity of cargo is determined by clathrin binding

Question 14

Mechanisms to target proteins to the correct compartment include all of the following
EXCEPT:
a Transport by vesicles.
b Transport by protein translocators.
c Gating through a pore.
d Transport through an aquaporin beta barrel

Answer 14

d Transport through an aquaporin beta barrel

Question 15

(Q036) Vesicles from the ER enter the Golgi at the
a trans Golgi network.
b cis Golgi network.
c medial cisternae.
d trans cisternae.

Answer 15

b cis Golgi network.

Question 16

(Q007) Proteins that are fully translated in the cytosol and lack a sorting signal will end up in the
a mitochondria.
b interior of the nucleus.
c cytosol.
d nuclear membrane.

Answer 16

c cytosol.

Question 17

All of the following targeting sequences are cleaved off during the import process
EXCEPT:
a the nuclear localization sequence
b The mitochondrial targeting sequence
c The ER signal sequence
d The chloroplast targeting sequence

Answer 17

a the nuclear localization sequence

Question 18

Examples of endocytosis include all the following EXCEPT:
a transcytosis
b uptake of glucose from the intestinal lumen
c phagocytosis
d pinocytosis

Answer 18

b uptake of glucose from the intestinal lumen

Question 19

What enzymatic activity does a G protein have?
a Kinase activity
b Translocase activity
c GTPase activity
d Phosphatase activity

Answer 19

c GTPase activity

Question 20

Which of the following is NOT true?
a Addition of a phosphoryl group on a protein adds two negative charges to the protein
b Trimeric G proteins are inactive when they exist as a trimer
c Binding of GTP to a G protein will always result in its activation
d Phosphorylation of a protein will always result in its activation

Answer 20

d Phosphorylation of a protein will always result in its activation

Question 21

Trimeric G proteins:
a Are active when they exist as a trimer
b Do not interact with 7-transmembrane-domain receptor proteins (also known as GPCRs)
c Are only active when all the subunits separate so they can act independently
d Bind a guanine nucleotide in their alpha subunit

Answer 21

d Bind a guanine nucleotide in their alpha subunit

Question 22

Which of the following is NOT true for the signal transduction pathway shown below:
a The second messenger Ca2+ acts to trigger opening of the chloride channel, which makes the neuron more likely to reach the threshold to send an action potential to the brain.
b The trimeric G protein is kept at the membrane by the presence of lipid tails
c GTP-bound G-alpha subunit activates adenylyl cyclase to produce the second messenger
cAMP.
d After binding its receptor, the odorant is internalized via receptor-mediated endocytosis

Answer 22

d After binding its receptor, the odorant is internalized via receptor-mediated endocytosis

Question 23

The pleckstrin homology (PH) domain binds:
a proline-rich motif
b phosphoserine
c phosphorylated inositol
phospholipid
d phosphotyrosine

Answer 23

c phosphorylated inositol
phospholipid

Question 24

Which of the following describes negative feedback regulation?
a. a component acts to further activate the signaling pathway and enhance the cell’s response
b A component amplifies the signal for a more robust response
c a component late in the pathway inhibits an enzyme early in the pathway
d A component generates an all-or-none, switch-like mechanism

Answer 24

c a component late in the pathway inhibits an enzyme early in the pathway

Question 25

(Q028) Akt promotes the survival of many cells by affecting the activity of Bad and and Bcl2. Which of the following statements is FALSE?
a In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2.
b In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active.
c In the absence of a survival signal, Bad is phosphorylated.
d In the presence of a survival signal, Akt is phosphorylated

Answer 25

c In the absence of a survival signal, Bad is phosphorylated.

Question 26

In the following olfactory signal transduction pathway, what is responsible for the
“adaptation” or “desensitization” that occurs after prolonged exposure to the odorant?
a Binding of the Ca2+ by calmodulin
b Degradation of the cAMP by phosphodiesterase
c Inhibition of the odorant receptor by G-alpha
d Inhibition of the odorant receptor by ORK and PKA

Answer 26

d Inhibition of the odorant receptor by ORK and PKA

Question 27

(Q026) Which of the following statements is TRUE?
a Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP.
b Dimerization of GPCRs leads to Gα activation.
c PI 3-kinase phosphorylates a lipid in the plasma membrane.
d MAP kinase is important for phosphorylating MAP kinase kinase.

Answer 27

c PI 3-kinase phosphorylates a lipid in the plasma membrane

Question 28

(Q023) A protein kinase can act as an integrating device in signaling if it
a initiates a phosphorylation cascade involving two or more protein kinases.
b phosphorylates more than one substrate.
c catalyzes its own phosphorylation.
d is activated by two or more proteins in different signaling pathways.

Answer 28

d is activated by two or more proteins in different signaling pathways.

Question 29

(Q006) Which of the following statements is TRUE?
a A cell-surface receptor capable of binding only one type of signal molecule can
mediate only one kind of cell response.
b To function, all extracellular signal molecules must be transported by their
receptor across the plasma membrane into the cytosol.
c Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.
d Any foreign substance that binds to a receptor for a normal signal molecule will
always induce the same response that is produced by that signal molecule on the
same cell type.

Answer 29

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

Question 30

(Q002) 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 paracrine
d endocrine

Answer 30

a. contact-dependent

Question 31

Which of the following types of cell signaling is long range and uses hormones as signals?
a neuronal
b endocrine
c contact-dependent
d paracrine

Answer 31

b endocrine

Question 32

(Q001) When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a
a neurotransmitter.
b scaffold.
c hormone.
d dissolved gas.

Answer 32

c hormone.

Question 33

(Q027) The activation of the serine/threonine protein kinase Akt requires phosphoinositide 3-kinase (PI 3-kinase) to
a activate the RTK.
b create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane.
c create DAG.
d directly phosphorylate Akt.

Answer 33

b create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane.

Question 34

(Q031) Which of the following statements is FALSE?
a Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription.
b Some signal molecules are transmembrane proteins.
c Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.
d Nucleotides and amino acids can act as extracellular signal molecules.

Answer 34

c Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.

Question 35

Effector proteins can include all of the following EXCEPT:
a cytoskeletal protein
b cAMP
c transcription factor
d metabolic enzyme

Answer 35

b cAMP

Question 36

The enzyme that synthesizes cAMP is:
a cyclooxygenase
b adenylyl cyclase
c polyadenylase
d guanylyl cyclase

Answer 36

b adenylyl cyclase

Question 37

During fertilizaton:
a A GPCR is activated that signals a kinase to initiate transcription to inhibit polyspermy
b No signaling can occur until after the sperm nucleus has fused with the egg nucleus
c Na+ channels open to trigger an action potential to inhibit polyspermy
d Rapid diffusion of a wave of Ca2+ across the egg inhibits polyspermy

Answer 37

d Rapid diffusion of a wave of Ca2+ across the egg inhibits polyspermy

Question 38

In a typical human secretory cell, which of the following membranes has the largest surface area?
a rough ER
b plasma membrane
c inner nuclear membrane
d smooth ER

Answer 38

a rough ER

Question 39

Sorting information that directs trafficking or localization within the cell may be found on all of the following EXCEPT:
a signal sequence
b chaperone
c NLS
d SNARE protein

Answer 39

b chaperone

Question 40

Q013) Which of the following statements is TRUE?
a Most mitochondrial proteins are not imported from the cytosol but are synthesized inside the mitochondria.
b Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.
c The signal sequences on mitochondrial proteins are usually at the C-terminus.
d Mitochondrial proteins cross the membrane in their native, folded state.

Answer 40

b Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.

Question 41

(Q026) Which of the following protein families are NOT involved in directing transport vesicles to the target membrane?
a SNAREs
b tethering proteins
c adaptins
d Rabs

Answer 41

c adaptins

Question 42

(Q018) In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins?
a the nucleus
b on the rough ER
c in the cytosol
d in the lumen of the ER

Answer 42

c in the cytosol

Question 43

(Q038) Which of the following statements about phagocytic cells in animals is FALSE?
a Phagocytic cells extend pseudopods that surround the material to be ingested.
b Phagocytic cells can engulf invading microorganisms and deliver them to their lysosomes for destruction.
c Phagocytic cells scavenge dead and damaged cells and cell debris.
d Phagocytic cells are important in the gut to take up large particles of food.

Answer 43

d Phagocytic cells are important in the gut to take up large particles of food.

Question 44

(Q017) After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode?
a ER membrane proteins
b plasma membrane proteins
c soluble secreted proteins
d all of these answers are correct

Answer 44

d all of these answers are correct

Question 45

Which of the following is NOT required for targeting and import of a mitochondrial protein?
a an N-terminal amphipathic targeting signal sequence
b a signal recognition particle (SRP) that recognizes the signal sequence and arrests translation until the ribosome can dock at the mitochondrial translocator
c protein unfolding during translocation
d involvement of chaperones to unfold and refold the protein before and during mitochondrial import

Answer 45

b a signal recognition particle (SRP) that recognizes the signal sequence and arrests translation until the ribosome can dock at the mitochondrial translocator

Question 46

One of the three types of GTP-binding proteins, often called “G-proteins”, are membrane bound. These are the:
a monomeric GTP-binding proteins
b trimeric GTP-binding proteins
c G-protein coupled receptors
d Elongation factor GTP-binding proteins

Answer 46

b trimeric GTP-binding proteins

Question 47

Which of the following is NOT true?
a GDIs are necessary for G proteins to release GDP so they can bind GTP
b G proteins can hydrolyze GTP on their own but it is very slow
c G proteins can release GDP on their own but at an extremely slow rate
d GAP proteins stimulate the rate of GTP hydrolysis by a G protein

Answer 47

a GDIs are necessary for G proteins to release GDP so they can bind GTP

Question 48

All of the following is true about RTKs EXCEPT:
a Dimerization by other means, such as IgG antibody binding two RTKs to bring them together, can result in activation
b They are receptors that, when activated will phosphorylate a serine residue on their partner
c They are integral membrane proteins that can relay extracellular signals to the inside of a cell.
d Ligand binding causes dimerization

Answer 48

b They are receptors that, when activated will phosphorylate a serine residue on their partner

Question 49

The Src homology 2 domain (SH2) binds:
a proline-rich motif
b phosphotyrosine
c phosphorylated phosphinositol phospholipid
d cAMP

Answer 49

b phosphotyrosine

Question 50

(Q030) All members of the nuclear receptor family
a do not undergo conformational changes.
b are found only in the cytoplasm.
c are cell-surface receptors.
d interact with signal molecules that diffuse through the plasma membrane.

Answer 50

d interact with signal molecules that diffuse through the plasma membrane.

Question 51

What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute?
a one that involves the firing of an action potential along a neuron
b one that involves the release of secretory vesicles
c one that uses a phosphorylation event to activate an enzyme
d one that involves a change in gene expression

Answer 51

d one that involves a change in gene expression

Question 52

(Q029) When the cytosolic tail of the __________ receptor is cleaved, it migrates to the nucleus and affects gene regulation.
a G-protein coupled
b nuclear
c Notch
d growth factor

Answer 52

c Notch

Question 53

The pleckstrin homology (PH) domain binds:
a phosphotyrosine
b phosphoserine
c proline-rich motif
d phosphorylated inositol phospholipid

Answer 53

d phosphorylated inositol phospholipid

Question 54

Which of the following signaling pathways would be likely to trigger the most rapid cell response?
a Adrenaline binds to a GPCR to activate a cyclic AMP signaling pathway that triggers glycogen breakdown
b Nerve growth factor binds to a receptor tyrosine kinase to activate a signaling pathway that enhances the transcription of Bcl2, a protein that suppresses cell death
c Platelet-derived growth factor binds to a RTK to activate a signaling pathway that stimulates cell proliferation at the site of a wound
d Acetylcholine binds to anion-channel-coupled receptor that allows Na+ to flow down its electrochemical gradient, triggering contraction of a skeletal muscle cell

Answer 54

d Acetylcholine binds to anion-channel-coupled receptor that allows Na+ to flow down its electrochemical gradient, triggering contraction of a skeletal muscle cell

Question 55

A protein kinase’s activity can be modulated in a number of different ways that include all of the following EXCEPT:
a Packaging it in an LDL particle to sequester it from potential substrates.
b Binding to a “pseudosubstrate” domain to block its ability to bind to a natural substrate
c Phosphorylation by another kinase (which can have a positive or a negative effect on its activity level, depending on the example)
d Tethering or anchoring the kinase to a specific location (which could allow it to be active or could prevent its activity, depending on the example)

Answer 55

a Packaging it in an LDL particle to sequester it from potential substrates.

Question 56

(Q024) Which of the following mechanisms is NOT directly involved in inactivating an activated RTK?
a dephosphorylation by serine/threonine phosphatases
b digestion of the RTK in lysosomes
c removal of the RTK from the plasma membrane by endocytosis
d dephosphorylation by protein tyrosine phosphatases

Answer 56

a dephosphorylation by serine/threonine phosphatases

Question 57

Which type of cell-surface receptor(s), when activated, catalyze(s) a reaction inside the cell?
a enzyme-coupled receptors AND G-protein coupled receptors
b enzyme-coupled receptors
c ion-channel-coupled receptors
d G-protein coupled receptors

Answer 57

b enzyme-coupled receptors

Question 58

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 mimics the ligand of ERC1
b addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive
c addition of a drug that prevents GTP hydrolysis by Gα.
d addition of a drug that activates adenylyl cyclase

Answer 58

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

Question 59

All of the following are examples of second messengers EXCEPT:
a Ca2+
b cAMP
c IP3
d Na+

Answer 59

d Na+

Question 60

ATP is important for chaperone protein function. Why would protein import into mitochondria be disrupted if ATP were depleted from inside mitochondria?
a The protein could slip back out of the mitochondria during transport
b The translocation apparatus would be unable to function without ATP hydrolysis
c The signal sequence would not be recognized on the mitochondrial protein
d The protein would be blocked from entering the translocation apparatus

Answer 60

a The protein could slip back out of the mitochondria during transport

Question 61

The “endomembrane system” includes:
a mitochondrial inner membrane
b Golgi apparatus
c mitochondrial outer membrane
d clathrin

Answer 61

b Golgi apparatus

Question 62

(Q008) Signal sequences that direct proteins to the correct compartment are
a added to a protein by a protein translocator.
b added to proteins through post-translational modification.
c encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.
d always removed once a protein is at the correct destination.

Answer 62

c encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination.

Question 63

What normal process is blocked by cleavage and inhibition of SNARE proteins?
a fusion of vesicles with target membranes
b docking of vesicles to target membranes
c budding of vesicles from the endoplasmic reticulum
d entry of proteins with the ER signal sequence into the ER lumen

Answer 63

a fusion of vesicles with target membranes

Question 64

A person with a PDH deficiency was identified and found to have a point mutation that resulted in an R –> P substitution in the first 10 amino acids of the newly synthesized E1alpha subunit. Their cells showed a decrease in the import of the E1alpha subunit into mitochondria. Which of the following could explain their disease symptoms?
a The mutant protein is more tightly folded preventing the translocator from unfolding the E1alpha protein.
b Chaperone proteins within the mitochondria are unable to bind the E1alpha subunit.
c The signal sequence is unable to be cleaved off of E1alpha resulting in Elalpha staying in the cytoplasm.
d The mitochondrial signal sequence of E1alpha is not being recognized by the import receptor.

Answer 64

d The mitochondrial signal sequence of E1alpha is not being recognized by the import
receptor.

Question 65

V-SNARES participate directly in:
a uncoating of the vesicle
b movement of the vesicle along cytoskeletal filaments
c docking of the vesicle to the target organelle
d assembly or formation of the transport vesicle

Answer 65

c docking of the vesicle to the target organelle

Question 66

(Q012) Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport?
a Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils
b Nuclear transport receptors would be unable to enter the nucleus.
c Nuclear transport receptors would be unable to bind cargo.
d Nuclear transport receptors would be unable to release their cargo in the nucleus.

Answer 66

d Nuclear transport receptors would be unable to release their cargo in the nucleus

Question 67

GTPase switch proteins such as ras:
a synthesize GTP from GDP
b are active when bound to GDP but inactive when bound to GTP
c Are converted from the active to inactive state by a guanine nucleotide exchange factor
d are active when bound to GTP but inactive when bound to GDP

Answer 67

d are active when bound to GTP but inactive when bound to GDP

Question 68

(Q012) The length of time a G protein will signal is determined by the
a activity of phosphatases that turn TP into GDP.
b degradation of the G protein after Ga separates from GBy.
c activity of phosphatases that turn off G proteins by dephosphorylating Ga.
d GTPase activity of Ga.

Answer 68

d GTPase activity of Ga.

Question 69

RTKs can activate the enzyme phosphoinositide 3-kinase, which phosphorylates inositol phospholipids. These phospholipids then do what?
a activate ras
b serve as phosphate donors in phosphorylation reactions
c serve as a docking site that recruit specific intracellular signaling proteins to the plasma membrane
d activate G proteins

Answer 69

c serve as a docking site that recruit specific intracellular signaling proteins to the plasma membrane

Question 70

A typical signaling pathway for a steroid hormone involves:
a Steroid hormone crosses membrane to bind intracellular (or intranuclear) receptor –> receptor underses allosteric change - -> receptor now acts as a transcription factor to turn on gene expression
b Steroid hormone binds to RTK –> activation of RTK promotes assembly of signaling complex –> signaling complex activates a kinase cascade - -> different effector proteins change cell behavior
c Steroid hormone binds to GPCR –> trimeric G protein is activated to produce cAMP and Ca2+ second messengers -> effector proteins activated to change cytoskeleton and cell morphology
*cess
d Steroid hormone activates nitric oxide synthase to produce NO –> NO diffuses to neighboring muscle cells –> muscle relaxation is triggered

Answer 70

a Steroid hormone crosses membrane to bind intracellular (or intranuclear) receptor –> receptor underses allosteric change - -> receptor now acts as a transcription factor to turn on gene expression

Question 71

(Q003) Which of the following statements is TRUE?
a The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells.
b Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism.
c Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal.
d The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.

Answer 71

d The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling.

Question 72

(Q022) The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization?
a changing the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid
b changing the tyrosines that are normally phosphorylated on RGFR dimerization to alanines
c a mutation that prevents RGFR from binding to RGF

Answer 72

c a mutation that prevents RGFR from binding to RGF

Question 73

Nitric oxide:
a Is the primary signaling molecule in plants
b Is an example of an endocrine signal
c Has a long half-life.
d Is a second messenger that rapidly diffuses through membranes

Answer 73

d Is a second messenger that rapidly diffuses through membranes

Question 74

(Q019) The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by
a activating a receptor tyrosine kinase.
b activating an intracellular protein kinase.
c diffusing into cells and stimulating the cyclase directly.
d activating a G protein.

Answer 74

c diffusing into cells and stimulating the cyclase directly.

Question 75

(Q037) Which of the following statements about secretion is TRUE?
a Vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received by the cell.
b The signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles.
c Proteins destined for constitutive exocytosis aggregate as a result of the acidic pH of the trans Golgi network.
d The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell’s exterior.

Answer 75

d The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell’s exterior.

Question 76

Proteins encoded by nuclear genes and destined for the mitochondrial matrix are:
a able to diffuse into the mitochondrial intermembrane space first
b transported across the membrane as a folded protein
c synthesized on ribosomes on the rough ER
d in possession of an amphipathic signal sequence for targeting to the mitochondria

Answer 76

d in possession of an amphipathic signal sequence for targeting to the mitochondria

Question 77

(Q007) Which of the following statements about molecular switches is FALSE?
a A GTP-binding protein exchanges its bound GDP for GTP to become activated.
b Protein kinases transfer the terminal phosphate from ATP onto a protein.
c Serine/threonine kinases are the most common types of protein kinase.
d Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off.

Answer 77

d Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off.

Question 78

Shown below is a diagram of how theoretical intracellular signaling pathways could integrate incoming signals to produce a coordinated cell response. Which signal(s)
would lead to activation of both kinase 1 and kinase 2?
A. signal C
B. signals A and C
C. signals C and D
D. signals A and D

Answer 78

D. signals A and D

Question 79

Q034) Figure 16-34 shows that intracellular signaling pathways can be highly interconnected.
From the information in Figure 16-34, which of the following statements is FALSE?
A. Ras is activated only when the RTK is active and not when the GPCR is active.
B. CaM-kinase is only activated when the GPCR is active and not when the RTK is active.
C. The GPCR and the RTK both activate phospholipase C.
D. Activation of either the GPCR or the RTK will lead to activation of transcriptional regulators

Answer 79

B. CaM-kinase is only activated when the GPCR is active and not when the RTK is active.