How do cells in the body of a multicellular organism usually communicate with each other?

a) intracellular messenger molecules

b) direct connection by cells through long projections

c) extracellular messenger molecules

d) electrical signals between cells

e) ion transport between cells

c

Sometimes an enzyme is activated by a receptor and brings about the cellular response by generating a second messenger. Such an enzyme is called a(n) __________.

a) activator

b) effector

c) affector

d) refractor

e) generator

b

No matter how the signal initiated by the binding of a ligand is transmitted (via a second messenger or by protein recruitment), what is the outcome of that signal?

a) A protein in the middle of an intracellular signaling pathway is activated.

b) A protein at the top of an intracellular signaling pathway is activated.

c) A protein at the top of an extracellular signaling pathway is activated.

d) A protein at the top of an intracellular signaling pathway is deactivated.

e) A protein at the bottom of an intracellular signaling pathway is activated.

b

Which of the following is (are) not characteristics of the pathways activated by second messengers?

a) Each signaling pathway consists of a series of distinct proteins that operate in sequence.

b) Each protein in the pathway typically acts by altering the conformation of the previous (upstream) protein in the series, an event that activates or inhibits the protein.

c) Alterations in the conformations of signaling proteins are often accomplished by protein kinases and protein phosphatases that, respectively, add or remove phosphate groups from other proteins.

d) Some phosphatases and protein kinases in the pathway have numerous proteins as their substrates; others act on only a single protein substrate or a single amino acid of a protein substrate.

e) Many of the protein substrates of the pathway enzymes are enzymes themselves, like other kinases and phosphatases, but they include ion channels, transcription factors and various regulatory molecules.

b

What kinds of responses are not initiated when signals traveling down signaling pathways reach their target proteins, which are usually involved in basic cellular processes?

a) a change in gene expression

b) a change in ion permeability

c) cessation of DNA synthesis and degradation of DNA

d) the death of the cell

e) an alteration of the activity of metabolic enzymes

c

At which site do virtually all of the signals that regulate the activities in which a cell is engaged originate?

a) at the cell surface

b) in the nucleus

c) in the nucleolus

d) in the endoplasmic reticulum

e) in the cell wall

a

The overall process in which information carried by extracellular messenger molecules is translated into changes that occur inside the cell is called ___________.

a) signal digestion

b) signal destruction

c) signal interaction

d) signal transduction

e) signal induction

d

If the receptor is degraded along with its ligand after internalization, what is the effect on the cell's ability to respond to a hormone?

1) The response is enhanced.

2) The cell has increased sensitivity to subsequent stimuli.

3) The cell has decreased sensitivity to subsequent stimuli.

4) The cell exhibits no change in responsiveness to subsequent stimuli.

a) 1

b) 2

c) 3

d) 4

e) 1 and 2

c

Proteins interact with one another, or with components of the cellular membrane, by means of _________.

1) specific types of interaction domains

2) intercellular glue

3) the SH3 domain

4) peptide bonds

a) 1

b) 2

c) 3

d) 4

e) 1 and 3

e

Most protein kinases transfer phosphate groups to which amino acid(s)?

1) glutamate

2) threonine

3) serine

4) tryptophan

a) 1

b) 2

c) 3

d) 4

e) 2 and 3

e

Which amino acids are known to be phosphorylated by protein kinases?

a) tyrosine, threonine, glycine

b) threonine, serine, tryptophan

c) serine, threonine, tyrosine

d) phenylalanine, serine, tyrosine

e) serine, leucine, tyrosine

c

Which molecule below is unlikely to act as either a neurotransmitter or hormone?

a) glucose

b) glycine

c) dopamine

d) eicosanoids

e) thyroid hormone

a

Which molecule below does not act as a neurotransmitter and a hormone?

a) glutamate

b) glycine

c) dopamine

d) eicosanoids

e) thyroid hormone

d

From what molecule are the steroids derived?

a) CO₂

b) cholesterol

c) glucose

d) phospholipids

e) glucagons

b

Which signaling molecules are nonpolar molecules containing 20 carbons that are derived from a fatty acid named arachidonic acid?

a) eicosanoids

b) steroids

c) acetylcholine

d) acetylsalicylic acid

e) epinephrine

a

Which of the following processes is not regulated by eicosanoids?

a) pain

b) inflammation

c) blood pressure

d) blood clotting

e) neurotransmission

e

What allows receptors for extracellular signaling molecules present on the responding cell's surface to recognize such molecules so readily?

a) They bind the signaling molecules with low affinity.

b) They bind the signaling molecules with high affinity.

c) They denature the signaling molecules.

d) They stabilize the signaling molecules.

e) They infiltrate the signaling molecules.

b

What role do activated steroid receptors play in the cell?

a) activation of inactive enzymes

b) inactivation of active enzymes

c) ligand-regulated transcription factors

d) opening of specific ion channels

e) activation of cytoplasmic proteins

c

Where are steroid receptors generally located and where do they bind the steroid hormone once it enters the cell?

a) They are located and bind the steroids in the cytoplasm.

b) They are located and bind the steroids in the middle of the cell membrane.

c) They are located and bind the steroids on the extracellular membrane surface.

d) They are located and bind the steroids on the intracellular membrane surface.

e) The receptors are located in the cytoplasm but they bind their ligands in the lysosomes.

a

Why are G-protein coupled receptors often known as 7TM receptors?

a) They have 7 tyrosine-methionine dipeptides in their structure.

b) They have 7 transmembrane b-pleated sheets.

c) They have 7 transmembrane a--helices.

d) They have 7 methionine-tryptophan dipeptides in their structure.

e) They have 7 nucleotides attached to their structure.

c

What is the largest protein superfamily encoded by animal genomes?

a) G-protein coupled receptors

b) RTKs

c) steroid receptors

d) tubulin superfamily

e) ligand-gated channels

a

Which of the following are not natural ligands that bind to G-protein coupled receptors?

a) hormones

b) neurotransmitters

c) chemoattractants

d) opium derivatives

e) steroid hormones

e

For many years, _______ was the only member of the GPCR superfamily to have its X-ray crystal structure determined.

a) rhodopsin

b) the steroid receptor

c) the insulin receptor

d) the glucagon receptor

e) the endocrine receptor

a

Why does rhodopsin have an unusually stable structure for a GPCR?

a) Its ligand is permanently bound to the protein.

b) A retinal group is permanently bound to the protein.

c) The protein molecule can only exist in a single conformation in the absence of a stimulus.

d) The protein molecule can only exist in a single conformation in the dark.

e) All of these are correct.

e

Place the events below in the correct order.

1) G protein binds to activated receptor forming a receptor-G protein complex

2) Release of GDP by the G protein

3) Change in conformation of the cytoplasmic loops of the receptor

4) Binding of GTP by the G protein

5) Increase in the affinity of the receptor for a G protein on the cytoplasmic surface of the membrane.

6) Binding of a hormone or neurotransmitter to a G-protein coupled receptor

7) Conformational shift in the  subunit of the G protein

a) 6 – 3 – 5 – 1 – 2 – 4 – 7

b) 3 – 6 – 5 – 1 – 7 – 2 – 4

c) 6 – 3 – 5 – 1 – 7 – 2 – 4

d) 6 – 7 – 3 – 5 – 1 – 2 – 4

e) 6 – 3 – 5 – 1 – 7 – 4 – 2

c

The subunits of the heterotrimeric G protein are called ___________ subunits.

a) a, b and c

b) a, b and d

c) a, b and g

d) a, g and d

e) g, d and h

c

Where is the guanine nucleotide-binding site of the G protein located?

a) on the G_a subunit

b) on the G_b subunit

c) on the G_g subunit

d) on the G_bg subunit

e) on all three subunits

a

Place the following events in the proper order.

1) Activation of one or more cellular signaling proteins.

2) Dissociation of G_a from the G protein complex.

3) Production of a second messenger, like cAMP.

4) Replacement of GDP by GTP on the G_a after interaction with an activated GPCR.

5) Conformational change in the G_a subunit causing a decreased affinity for the G_{b g} subunit.

6) G_a-subunit with its attached GTP activates an effector like adenylyl cyclase.

a) 4 – 5 – 2 – 6 – 3 – 1

b) 5 – 4 – 2 – 6 – 3 – 1

c) 4 – 6 – 2 – 5 – 3 – 1

d) 4 – 5 – 2 – 3 – 1 – 6

e) 1 – 5 – 2 – 4 – 3 – 6

a

Which heterotrimeric G proteins couple receptors to adenylyl cyclase via the activation of GTP-bound G_a subunits?

a) G_s family

b) G_q family

c) G_i family

d) G_12/13 family

e) G_r family

a

Which heterotrimeric G proteins function by inhibiting adenylyl cyclase?

a) G_s family

b) G_q family

c) G_i family

d) G_12/13 family

e) G_r family

c

Which heterotrimeric G proteins are less well characterized than the other G protein families and have had their inappropriate activation associated with excessive cell proliferation and malignant transformations?

a) G_s family

b) G_q family

c) G_i family

d) G_12/13 family

e) G_r family

d

The process that blocks active receptors from turning on additional G proteins is called ________.

a) hypersensitization

b) desensitization

c) hyposensitization

d) deactivation

e) sensitivitization

b

In order to begin desensitization, the ________ domain of the activated G protein-coupled receptor is phosphorylated by a specific enzyme called a(n) ________.

a) extracellular, G protein-coupled receptor kinase

b) extracellular, G protein-coupled receptor phosphatase

c) cytoplasmic, G protein-coupled receptor kinase

d) cytoplasmic, G protein-coupled receptor phosphatase

e) extracellular, GRK

c

GRKs are a small family of ________ protein kinases, most of which are localized to the _______ surface of the plasma membrane.

a) serine-threonine, cytoplasmic

b) serine-threonine, extracellular

c) tyrosine, cytoplasmic

d) tyrosine, extracellular

e) serine-tyrosine, cytoplasmic

a

What recruits cytoplasmic GRKs (G protein-coupled receptor kinases) to the plasma membrane?

a) inhibition of certain G proteins

b) destruction of the GPCRs

c) activation of GPCRs

d) inhibition of the GPCRs

e) destruction of the hormone

c

________ form a small group of proteins that bind to GPCRs and compete for binding to those GPCRs with heterotrimeric G proteins.

a) Stablins

b) Arrestins

c) Monomeric G proteins

d) G protein-coupled receptor kinases

e) Desensitizers

b

Arrestin binding to GPCRs __________.

a) causes the binding of additional G proteins

b) prevents further activation of additional G proteins

c) causes denaturation of G proteins

d) stabilizes G proteins

e) stabilizes GPCRs

b

While bound to phosphorylated GPCRs, to what else can arrestins bind?

a) G proteins

b) clathrin molecules in clathrin-coated pits

c) other arrestins

d) hormones

e) GRKs

b

What does the interaction between arrestin and clathrin promote?

a) the uptake of free hormone

b) the uptake of phosphorylated GPCRs into the cell by exocytosis

c) the uptake of phosphorylated GPCRs into the cell by endocytosis

d) the expulsion of phosphorylated GPCRs from the cell by exocytosis

e) the secretion of GPCRs

c

What happens to cells if the receptors are degraded once they are internalized?

a) The cells are able to make a magnified response to the same stimulus from the ligand in question.

b) The cells permanently lose sensitivity for the ligand in question.

c) The cells lose, at least temporarily, sensitivity for the ligand in question.

d) The cells remain sensitive to the ligand in question.

e) The cells expand.

c

How is signaling by an activated G_a subunit terminated?

a) The bound GTP is hydrolyzed to GMP.

b) The bound GDP is hydrolyzed to GTP.

c) The bound GTP is hydrolyzed to GDP.

d) The bound GDP is phosphorylated to GTP.

e) The G_a subunit releases GDP and binds GTP.

c

What is the function of carbon number 1 on the inositol ring of phosphatidylinositol?

a) It binds to steroid receptors.

b) It joins inositol to diacylglycerol.

c) It joins a phosphate group to diacyglycerol.

d) It joins glucose to diacylglycerol.

e) It joins two diacyglycerol molecules together.

b

What group of enzymes phosphorylates most of the carbons on inositol?

a) phospholipases

b) phosphoinositide kinases

c) phosphorylases

d) phosphodiesterases

e) phosphatases

b

What enzyme below does diacylglycerol (DAG) recruit and activate?

a) phosphatidylinositol (PI)-specific phospholipase C-b

b) protein kinase A

c) protein kinase C

d) glycogen phosphorylase

e) phosphorylase kinase

c

The effect of inositol triphosphate is usually transient because __________.

a) it is so stable

b) it is rapidly inactivated enzymatically

c) it is slowly activated enzymatically

d) it is so big

e) it is so small

b

In what form do animal cells store glucose?

a) glucogen

b) glycogen

c) agarose

d) amylose

e) amylopectin

b

Which cells secrete epinephrine?

a) a-cells in the pancreas

b) b-cells in the pancreas

c) D-cells in the pancreas

d) cortical cells in the adrenal gland

e) medulla cells in the adrenal gland

e

Which hormone is secreted by a-cells in the pancreas in response to low blood glucose levels?

a) insulin

b) glycogen

c) glucagon

d) epinephrine

e) somatostatin

c

What might cause a person to have an inability to detect a particular chemical in the environment that most other members of the population can perceive?

a) mutations is a specific gene encoding the odorant receptor for that particular chemical

b) mutations in the genes for all odorant molecules

c) mutations in the genes for G proteins

d) mutations in the genes for neurotransmitters

e) mutations in the gene for one neurotransmitter

a

Perception of sour tastes depends upon _________.

a) a compound interacting with a G protein coupled receptor on the receptor cell surface

b) sodium ions in the food that enter cation channels in the taste receptor plasma membrane, leading to a membrane depolarization

c) protons in the food that enter cation channels in the taste receptor plasma membrane, leading to a membrane depolarization

d) potassium ions in the food that enter cation channels in the taste receptor plasma membrane, leading to a membrane depolarization

e) protons in the food that enter cation channels in the taste receptor plasma membrane, leading to a membrane hyperpolarization

c

How many high-affinity sweet-taste receptors have been identified?

a) none

b) 30

c) 1

d) 10

e) 3

c

Where are the olfactory receptor cells located?

a) the brain

b) the nasal septum

c) the nasal mucosa

d) the surface of the tongue

e) the nasal serosa

c

Why do colds cause us to lose some of our appreciation for the taste of food?

a) The symptoms of colds interfere with the stimuli reaching the taste bud receptors, thus dulling the perception of taste.

b) The symptoms of colds prevent stimuli from reaching olfactory neurons efficiently, thus dulling the perception of taste.

c) Cold viruses raise the firing threshold of olfactory neurons, thus dulling the perception of taste.

d) Cold viruses lower the firing threshold of olfactory neurons, thus dulling the perception of taste.

e) Cold viruses denature olfactory neurons, thus dulling the perception of taste.

b

_________ are enzymes that phosphorylate specific tyrosine residues on protein substrates.

a) Protein tyrosinases

b) Protein-tyrosine kinases

c) Tyrosine pronases

d) Proteokinases

e) Tyrokinases

b

Which of the following features would be a requirement for a receptor that exhibits ligand-mediated dimerization?

a) The ligand has only one binding site for receptors.

b) The ligand has two binding sites for receptors.

c) The receptor must have a phenylalanine residue in a specific location.

d) The receptor must have a molecular weight of 50,000 daltons.

e) Ligand binding causes a conformational shift that reveals a binding site for another receptor.

b

Which of the following supports the ligand-mediated model of receptor dimerization?

a) Some growth and differentiation factors like PDGF or CSF-1 are composed of two similar or identical disulfide-linked subunits, each of which has a binding site for a receptor.

b) Ligands have been found to be small proteins.

c) Ligands have been found to be steroid hormones.

d) Ligands were found to bind to each other

e) Receptors have been shown to have multiple binding sites for ligands.

a

Which statement below is an accurate description of receptor-mediated dimerization?

a) Ligands act as allosteric regulators that turn on the ability of their receptors to form dimers.

b) Ligands act as allosteric inhibitors that turn on the ability of their receptors to form dimers.

c) Ligands act as allosteric inhibitors that turn off the ability of their receptors to form dimers.

d) Ligands act as allosteric regulators that turn off the ability of their receptors to form dimers.

e) Ligands act as bridging factors that allow the receptors to dimerize.

a

Once the kinase domain of receptor protein-tyrosine kinase has been activated, what does the activated receptor protein-tyrosine kinase do?

a) The receptor subunits denature.

b) Each receptor subunit phosphorylates its partner on tyrosine residues found in regions adjacent to the kinase domain.

c) Each receptor subunit phosphorylates itself on tyrosine residues found in regions adjacent to the kinase domain.

d) The receptor subunits dephosphorylate each other.

e) The receptor subunits refold into a more effective conformation.

b

What phosphorylates the tyrosine residues found on docking proteins?

a) a G protein coupled receptor

b) a receptor protein-tyrosine kinase

c) a cytoplasmic protein-tyrosine kinase

d) adaptor proteins

e) receptor protein phosphatases

b

Which of the following contains an SH2 domain together with a tyrosine phosphorylation site that can act as a binding site for the SH2 domain of an identical molecule leading to dimerization?

a) adaptor proteins

b) docking proteins

c) transcription factors

d) enzymes

e) All of these are correct.

c

What event is usually responsible for terminating signal transduction by RTKs?

a) dephosphorylation of the receptor

b) degradation of the ligand

c) receptor internalization

d) phosphorylation of the receptor

e) acetylation of the receptor

c

________ is a small protein that is linked covalently to other proteins, thereby marking those proteins for internalization or degradation.

a) Chaperonin

b) Ubiquitin

c) Proinsulin

d) Transcriptin

e) Tubulin

b

Viruses that carry their genetic information in the form of RNA are called ________.

a) viria

b) retroviruses

c) reverse transcriptases

d) retrons

e) provirions

b

Genes that enable viruses to transform normal cells into tumor cells are called _________.

a) oncogenes

b) cancogenes

c) haplogenes

d) tumor enhancer genes

e) transformer genes

a

What kind of enzyme is the RAS gene product, the Ras protein?

a) an ATPase

b) a kinase

c) a phosphodiesterase

d) a GTPase

e) a phosphatase

d

What holds Ras at the inner surface of the plasma membrane?

a) weak interactions with the phospholipid head groups

b) weak interactions with integral membrane proteins

c) hydrophilic interactions of the Ras protein with the interior of the phospholipid bilayer

d) attachment to a lipid group that is embedded in the inner leaflet of the bilayer

e) attachment to a carbohydrate group that is embedded in the inner leaflet of the bilayer

d

How is Ras activity turned off?

a) It is turned off by phosphorylation.

b) It is turned off by hydrolysis of its bound GTP to GDP.

c) It is turned off by hydrolysis of its bound GDP to GTP.

d) It is turned off by an allosteric inhibitor.

e) It is turned off by hydrolysis of its bound GTP to GMP.

b

In cells exposed to stressful stimuli, like X-rays or damaging chemicals, what response does the MAP kinase cascade coordinate?

a) cell proliferation

b) withdrawal from the cell cycle

c) rapid differentiation

d) slowing of the Krebs cycle

e) a loss of sensory ability

b

What is the reason for the withdrawal of cells from the cell cycle after exposure to stressful stimuli, like X-rays and damaging chemicals?

a) It gives the cell time to repair damage resulting from such adverse conditions.

b) It allows the cell to initiate programmed cell death.

c) It allows cells to initiate sodium transport.

d) It allows the cell to secrete defensive chemicals.

e) It gives the cell time to switch its developmental pathways.

a

Specificity in MAP kinase pathways is sometimes achieved by spatial localization of the pathway's component proteins. Spatial localization of these components is done by structural (i.e., nonenzymatic) proteins called _____________.

1. a) sequestration proteins
2. b) partitioning proteins
3. c) scaffolding proteins
4. d) framework proteins
5. e) spatial organization proteins

c

Two ab heterodimers of the insulin receptor are held together by ____ between the _______.

a) ionic bonds, a chains

b) ionic bonds, b chains

c) disulfide bonds, a chains

d) disulfide bonds, b chains

e) disulfide bonds, a chain of one heterodimer and the  chain of the other

c

What part of an insulin-receptor substrate binds to tyrosine phosphorylation sites on the activated insulin receptor?

a) an N-terminal PH domain

b) a PTB domain

c) a long tail containing tyrosine phosphorylation sites

d) a C-terminal PH domain

e) a PKB domain

b

The enzyme below that has been identified as a negative regulator of glycogen synthase is ______.

a) glycogen phosphorylase

b) glycogen phosphorylase kinase

c) glycogen synthase kinase-3

d) insulin synthase kinase

e) protein kinase A

c

What is responsible for deactivating glycogen synthase kinase-3?

a) its phosphorylation by PKB

b) its dephosphorylation by protein phosphatase 1

c) its dephosphorylation by PKB

d) its phosphorylation by protein phosphatase 1

e) its degradation by PKB

a

Type I diabetes is caused by ________.

a) degradation of insulin in the bloodstream

b) an inability to produce insulin

c) a decrease in the ability of target cells for insulin to respond to the presence of the hormone

d) insulin resistance

e) an overproduction of insulin

b

The concentration of calcium ions in the ER lumen, the plant cell vacuole and the extracellular space are on average more than _______ times higher than in the cytosol.

a) 10

b) 100

c) 1,000

d) 10.000

e) 1,000,000

d

Following a nerve impulse, what triggers the opening of plasma membrane voltage-gated Ca2+ channels?

a) membrane hyperpolarization

b) binding of an appropriate ligand

c) membrane depolarization

d) membrane hypopolarization

e) binding of K⁺ ions

c

How is the distribution of free calcium ions in the living cell detected?

a) fluorescent probes that emit light in the presence of calcium ions

b) antibodies bound to ferritin

c) an electron microscope

d) autoradiography and the distribution of radioisotope

e) NMR imaging

a

What generally triggers the release of calcium ions by ryanodine receptors?

a) potassium efflux

b) sodium influx

c) an action potential

d) IP₃ release

e) IP₃ uptake

c

Among the agents that can cause ryanodine receptors to open are _______ ions, in a phenomenon called _______.

a) calcium, calcium-integrated calcium release

b) calcium, calcium-induced calcium release

c) potassium, potassium-induced calcium release

d) chlorine, chlorine-induced calcium release

e) copper, copper-induced calcium release

b

What is activated by calcium ions entering an egg cell just after fertilization?

a) protein kinase A

b) insulin

c) cyclin-dependent kinases that drive the zygote toward its first mitotic division

d) cyclin-dependent kinases that drive the zygote toward its first meiotic division

e) glucagon-dependent kinases that drive the zygote toward its first mitotic division

c

What can cause the stockpile of intracellular calcium ions to be depleted?

1) periods of repeated cellular responses

2) a paucity of cellular responses

3) crystallization of calcium ions with chlorine ions

4) crystallization of calcium with phosphate ions

a) 1

b) 2

c) 3

d) 4

e) 3 and 4

a

Ora1 is a tetrameric _______ that has been identified as being involved in a particular type of inherited human immune deficiency that results from a lack of Ca2+ stores in ________.

a) Ca^2+--ion channel, B lymphocytes

b) Ca^2+--ion pump, B lymphocytes

c) Ca^2+-ion channel, T lymphocytes

d) Ca^2+--ion pump, T lymphocytes

e) Ca^2+--ion channel, macrophages

c

What is the name of a calcium-binding protein that acts in conjunction with calcium to bring about the responses associated with cytoplasmic rises in calcium ion concentration?

a) calpectin

b) calmodulin

c) calcariain

d) callistin

e) modulocalcin

b

In which organism below has calmodulin not been found?

a) plants

b) animals

c) bacteria

d) yeasts

e) humans

c

Why does calcium not bind to calmodulin in an nonstimulated cell?

a) Calmodulin's affinity for calcium ions is too low to allow binding in an nonstimulated cell.

b) Calmodulin's affinity for calcium ions is too high to allow binding in an nonstimulated cell.

c) In an nonstimulated cell, calcium ions are destroyed.

d) In an nonstimulated cell, calcium ions are produced.

e) In an nonstimulated cell, calcium ions preferentially bind to another protein in the cytosol.

a

The activation of a common effector by signals from a variety of unrelated receptors, each of which binds to its own ligand, is called _________.

a) divergence

b) convergence

c) crosstalk

d) transvergence

e) coherence

b

The passage of signals back and forth between different pathways is referred to as _________.

a) divergence

b) convergence

c) crosstalk

d) transvergence

e) coherence

c

What molecule is responsible for activating Rsk-2?

a) PKA

b) CREB

c) MAPKK

d) MAPK

e) cAMP

d

What inorganic gas has been shown to act as a second messenger that relaxes the smooth muscles of blood vessels?

a) NO

b) N₂O

c) nitrous oxide

d) CO

e) N₂

a

_____ is formed from the amino acid L-______ in a reaction catalyzed by the enzyme _____.

a) Nitrous oxide, arginine, nitrous oxide synthase

b) Nitric oxide, asparagine, nitric oxide synthase

c) Nitric oxide, alanine, nitric oxide synthase

d) Nitric oxide, arginine, nitric oxide synthase

e) Nitrous oxide, arginine, nitric oxide synthase

d

Why did the smooth muscle in cultured strips of aorta not respond to acetylcholine by relaxing, while the smooth muscle of aortic rings did?

a) Smooth muscle cells in aortic strips are physically incapable of relaxing under any circumstances.

b) Acetylcholine in the strips could not penetrate to the muscle cells while in the rings it could.

c) Smooth muscle cells in aortic rings express acetylcholine receptors, while those in strips do not.

d) The delicate endothelial layer in aortal strips had been rubbed away during dissection, while in aortal rings it remained intact.

e) The endothelial layer in aortal strips was abnormally thickened, while in aortal rings it was not.

d

n which of the following biological processes is nitric oxide not involved?

a) anticoagulation

b) neurotransmission

c) smooth muscle relaxation

d) visual perception

e) hearing

e

What agent made by endothelial cells makes blood vessel smooth muscle cells relax?

a) nitrous oxide

b) acetylcholine

c) nitric oxide

d) cAMP

e) cGMP

c

What stimulus triggered by the binding of acetylcholine then activates nitric oxide synthase?

a) a rise in cytoplasmic Ca²⁺ concentration

b) a drop in cytoplasmic Ca²⁺ concentration

c) an action potential

d) cellular hyperpolarization

e) release of cGMP

a

How were nitroglycerine's therapeutic benefits discovered?

a) through careful drug testing

b) the fact that dynamite factory workers with heart conditions had less angina on days that they worked

c) the fact that dynamite factory workers with heart conditions had more angina on days that they worked

d) by reading the literature

e) by prayer

b

How does Viagra enhance erectile function of the penis?

a) by inhibiting nitric oxide release

b) by inhibiting guanylyl cyclase activity

c) by preventing cGMP production

d) by inhibiting cGMP phosphodiesterase

e) by inhibiting cGMP phosphatase

d

The addition of nitric oxide to the sulfhydryl groups of certain cysteine residues in a number of proteins, including hemoglobin, Ras, ryanodine channels and caspases alters the activity, turnover or interactions of the proteins. This posttranslational modification is called _______.

a) S-nitrosylation

b) SH-nitrosylation

c) sulfhydration

d) nitrofruition

e) nitric acidification

a

To which amino acid is nitric oxide added, altering the activity, turnover and/or interactions of proteins like hemoglobin, Ras, ryanodine channels and caspases?

a) alanine

b) cysteine

c) methionine

d) asparagine

e) phenylalanine

b

How does the immune system manage to avoid recognizing and attacking normal cells within the body?

a) The body never makes T lymphocytes that can react against normal cells within the body.

b) T lymphocytes that have the ability to recognize normal cells within the body are eliminated by apoptosis early in the development of the immune system.

c) Normal body cells are coated with a special secreted protective proteoglycan that prevents the immune system from attacking them.

d) Normal body cells are coated with a special secreted protective glycoprotein that prevents the immune system from attacking them.

e) Normal body cells are coated with a mixture of special secreted protective proteoglycans and glycoproteins that prevents the immune system from attacking them.

b

What gene in C. elegans was found to play a critical role in apoptosis?

a) CED-3

b) DEG-3

c) NSO-1

d) Eco R1

e) CEL-3

a

A family of proteins homologous to the products of the CED-3 gene in C. elegans has been discovered in mammals. What is this family of proteins called?

a) capsidases

b) caspases

c) capsasins

d) capsulases

e) apoptases

b

How is caspase-activated DNase (CAD) activated?

a) A caspase cleaves CAD, activating it.

b) A caspase cleaves an activator of CAD, turning it on and causing it to activate CAD.

c) A caspase cleaves a CAD inhibitor, relieving the CAD of inhibition.

d) A caspase binds to CAD allosterically, activating it.

e) None of these are correct.

c

The _________ pathway of apoptosis is one in which external stimuli activate apoptosis via a signaling pathway.

a) extrinsic

b) external

c) intrinsic

d) peripheral

e) integral

a

The _________ pathway of apoptosis is one in which internal stimuli activate apoptosis.

a) extrinsic

b) external

c) intrinsic

d) peripheral

e) integral

c

What is the name of an extracellular messenger protein that is named for its ability to kill tumor cells and also serves as an apoptotic stimulus?

a) tumor angiogenesis factor

b) tumor death factor

c) tumor necrosis factor

d) necromancer factor

e) tumorigenic factor

c

Evidence suggests that TNFR1 is present in the plasma membrane as __________.

a) a preassembled trimer

b) a preasembled dimer

c) a disassembled trimer

d) a disassembled dimer

e) a tetrameric trimer

a

Each TNFR1 receptor subunit has a cytoplasmic domain with a segment of about 70 amino acids that mediates protein-protein interactions. This domain of the receptor is referred to as the ______ domain.

a) central

b) morte

c) death

d) terminal

e) cytoplasmic

c

Bcl-2 acts as a(n) ________ by promoting ___________.

a) oncogene, cell division

b) haplogene, survival of potential cancer cells that would otherwise die by apoptosis

c) oncogene, survival of potential cancer cells that would otherwise die by apoptosis

d) cancer gene, survival of potential cancer cells that would otherwise die by apoptosis

e) haplogene, cell division

c

Once activated, what does caspase-9 itself activate?

a) phospholipase C

b) protein kinase A

c) other initiator caspases

d) downstream executioner caspases

e) downstream caspase-8

d