A) which induce changes in the cells that lead to cell fusion.
B) which produce more of the a factor in a positive feedback.
C) then one cell nucleus binds the mating factors and produces a new nucleus in the opposite cell.
D) stimulating cell membrane disintegration, releasing the mating factors that lead to new yeast cells.
E) which in turn releases a growth factor that stimulates mitosis in both cells.
A) They might compensate by receiving nutrients via a factor.
B) They could develop normally in response to neurotransmitters instead.
C) They could divide but never reach full size.
D) They might not be able to multiply in response to growth factors from nearby cells.
E) Hormones would not be able to interact with target cells.
A) Even in the simplest organisms, sexual reproduction required several coordinated responses by cells.
B) Multicellular eukaryotes required signals that were responded to by multiple organ systems.
C) Cells of several kinds of mating types needed to sort themselves to allow self-recognition.
D) Rooted plants required chemical diffusible signals that could travel throughout the organism.
E) Hormones required a mechanism for introducing changes in their target tissues.
A) hormonal signaling
B) autocrine signaling
C) paracrine signaling
D) endocrine signaling
E) synaptic signaling
A) formation of mating complexes
B) secretion of apoptotic signals
C) aggregation of bacteria that can cause cavities
D) secretion of substances that inhibit foreign bacteria
E) digestion of unwanted parasite populations
A) must physically and directly interact.
B) produce signal molecules that change themselves so they can interact with one another.
C) produce response molecules that diffuse to other yeast cells.
D) secrete molecules that result in response by other yeast cells.
E) mate, after which the new cells secrete hybrid signals.
A) Plant hormones interact primarily with intracellular receptors.
B) Plant hormones may travel in air or through vascular systems.
C) Animal hormones are found in much greater concentration.
D) Plant hormones are synthesized from two or more distinct molecules.
E) Animal hormones are primarily for mating and embryonic development.
A) The growth factor is a paracrine signal.
B) The growth factor depends on osmosis.
C) The mammal only carries growth factor through the lymph.
D) The growth factor is an exocrine signal.
E) The growth factor is an endocrine signal.
B) relay molecule
D) signal molecule
E) endocrine molecule
A) the active site of an allosteric enzyme that binds to a specific substrate.
B) tRNA specifying which amino acids are in a polypeptide.
C) a metabolic pathway operating within a specific organelle.
D) an enzyme having an optimum pH and temperature for activity.
E) an antibody in the immune system.
A) It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
B) It could activate only the epinephrine system.
C) It would be able to carry out reception and transduction but would not be able to respond to a signal.
D) It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
E) It would employ a transduction pathway directly from an external messenger.
A) acting as a signal receptor that activates tyrosine kinases.
B) binding with a receptor protein that enters the nucleus and activates specific genes.
C) acting as a steroid signal receptor that activates ion channel proteins.
D) becoming a second messenger that inhibits adenylyl cyclase.
E) coordinating a phosphorylation cascade that increases spermatogenesis.
A) They regulate the synthesis of DNA in response to a signal.
B) They transcribe ATP into cAMP.
C) They initiate the epinephrine response in animal cells.
D) They control gene expression.
E) They regulate the synthesis of lipids in the cytoplasm.
A) G protein-coupled receptors
B) ligand-gated ion channels
C) steroid receptors
D) receptor tyrosine kinases
A) They lead to changes in intracellular ion concentration.
B) They open and close in response to protein signals.
C) They are only attached to one membrane surface: exterior or interior.
D) They preferentially bind with lipid or glycolipid signal molecules.
E) They change their conformation after binding with signal polypeptides.
A) The receptor molecules are themselves lipids or glycolipids.
B) The steroid/receptor complex can cross the nuclear membrane.
C) The unbound steroid receptors are quickly recycled by lysosomes.
D) The concentration of steroid receptors must be relatively high in most cells.
E) The receptor molecules are free to move in and out of most organelles.
A) If Herceptin is found in the breast lymph nodes of the patient.
B) If HER2, administered by injection, is in sufficient concentration.
C) If the patient’s cancer cells have detectable HER2.
D) If the patient’s genome codes for the HER2 receptor.
E) If the patient’s genome codes for the manufacture of Herceptin.
A) ligand-gated ion channels.
B) G protein-coupled receptors.
C) cyclic AMP.
D) receptor tyrosine kinases.
A) brings a conformational change to each protein.
B) requires binding of a hormone to a cytosol receptor.
C) cannot occur in yeasts because they lack protein phosphatases.
D) requires phosphorylase activity.
E) allows target cells to change their shape and therefore their activity.
A) a decrease in levels of cAMP as a result of bypassing the plasma membrane.
B) lower blood glucose by binding to liver cells.
C) interactions with insulin inside muscle cells.
D) interactions directly with glycogen phosphorylase.
E) elevation of cytosolic concentrations of cyclic AMP.
A) blockage of the synaptic signal
B) loss of transcription factors
C) insufficient ATP levels in the cytoplasm
D) low oxygen concentration around the cell
E) low levels of protein kinase in the cell
A) modifies a G protein involved in regulating salt and water secretion.
B) decreases the cytosolic concentration of calcium ions, making the cells hypotonic.
C) binds with adenylyl cyclase and triggers the formation of cAMP.
D) signals IP3 to act as a second messenger for the release of calcium.
E) modifies calmodulin and activates a cascade of protein kinases.
A) G protein-coupled receptor signaling
B) ligand-gated ion channel signaling
C) adenylyl cyclase activity
D) phosphatase activity
E) receptor tyrosine kinase activity
A) protein kinase activity
B) adenylyl cyclase activity
C) GTPase activity
D) protein phosphatase activity
E) phosphorylase activity
A) block the response of epinephrine
B) decrease the amount of cAMP in the cytoplasm
C) block the activation of G proteins in response to epinephrine binding to its receptor
D) prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm
E) block the activation of protein kinase A
A) protein kinase
B) protein phosphatase
A) phosphorylated proteins.
D) adenylyl cyclase.
E) activated G proteins.
A) that activates epinephrine receptors.
B) that increases cAMP production in liver cells.
C) to block G protein activity in liver cells.
D) that increases phosphorylase activity.
E) that keeps sugar molecules from crossing the plasma membrane of liver cells.
A) that mimics epinephrine and can bind to the epinephrine receptor.
B) that stimulates cAMP production in liver cells.
C) to stimulate G protein activity in liver cells.
D) that increases phosphodiesterase activity.
E) that does any of the above.
A) tyrosine kinases
B) serine/threonine kinases
D) phospholipase C
E) adenylyl cyclase
A) When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules.
B) In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP₃ and calcium.
C) In most cases, signal molecules interact with the cell at the plasma membrane and then enter the cell and eventually the nucleus.
D) Toxins such as those that cause botulism and cholera interfere with the ability of activated G proteins to hydrolyze GTP to GDP, resulting in phosphodiesterase activity in the absence of an appropriate signal molecule.
E) Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.
A) kinase activity and the addition of a tyrosine
B) phosphodiesterase activity and the removal of phosphate groups
C) GTPase activity and hydrolysis of GTP to GDP
D) phosphorylase activity and the catabolism of glucose
E) adenylyl cyclase activity and the conversion of cAMP to AMP
A) hydrolyzed cGMP to GMP.
B) hydrolyzed GTP to GDP.
C) phosphorylated GDP.
D) dephosphorylated cGMP.
E) removed GMP from the cell.
A) Most of the steps were already in place because they are steps in other pathways.
B) Multiple steps in a pathway require the least amount of ATP.
C) Multiple steps provide for greater possible amplification of a signal.
D) Each individual step can remove excess phosphate groups from the cytoplasm.
E) Each step can be activated by several G proteins simultaneously.
B) glycine and histidine
C) serine and threonine
D) glycine and glutamic acid
E) Any of the 20 amino acids are equally phosphorylated.
A) move the phosphate group of the transduction pathway to the next molecule of a series.
B) prevent a protein kinase from being reused when there is another extracellular signal.
C) amplify the transduction signal so it affects multiple transducers.
D) amplify the second messengers such as cAMP.
E) inactivate protein kinases and turn off the signal transduction.
A) Calcium ions are actively imported from the cytoplasm into the ER.
B) Calcium concentration is kept low in the cytoplasm because of its high usage level.
C) Calcium cannot enter the plasma membrane through ion channels.
D) Calcium levels in the blood or other body fluids are extremely low.
E) The Ca ions are recycled from other molecules in the ER.
A) removal of serine/threonine phosphate acceptors from transduction pathways in colon pre-cancerous growths
B) alteration of protein kinases in cell cycle regulation in order to slow cancer growth
C) increase in calcium ion uptake into the cytoplasm in order to modulate the effects of environmental carcinogens
D) expansion of the role of transduction inhibitors in the cells before they give rise to cancer
E) increase in the concentration of phosphodiesterases in order to produce more AMP
A) lower cytoplasmic levels of cAMP
B) an increase in receptor tyrosine kinase activity
C) a decrease in transcriptional activity of certain genes
D) an increase in cytosolic calcium concentration
E) a decrease in G protein activity
A) Estrogen is produced in very large concentration and therefore diffuses widely.
B) Estrogen has specific receptors inside several cell types, but each cell responds in the same way to its binding.
C) Estrogen is kept away from the surface of any cells not able to bind it at the surface.
D) Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.
E) The subcomponents of estrogen, when metabolized, can influence cell response.
A) ladderlike proteins that allow receptor-ligand complexes to climb through cells from one position to another
B) microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores
C) large molecules to which several relay proteins attach to facilitate cascade effects
D) relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing
E) proteins that can reach into the nucleus of a cell to affect transcription
A) removal of the receptor
B) activation of a different set of relay molecules
C) converting ATP to camp
D) incompatibility of the binding of the signal molecule to the receptor
A) increases the available concentration of phosphate.
B) decreases the amount of G protein in the membrane.
C) hydrolyzes GTP binding to G protein.
D) converts cGMP to GTP.
E) phosphorylates protein kinases.
A) The animal has as many genes as complex organisms, but finding those responsible is easier than in a more complex organism.
B) The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.
C) This plant has a long-studied aging mechanism that has made understanding its death just a last stage.
D) While the organism ages, its cells die progressively until the whole organism is dead.
E) All of its genes are constantly being expressed so all of its proteins are available from each cell.
A) The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled.
B) Its DNA and organelles become fragmented, it dies, and it is phagocytized.
C) The cell dies and the presence of its fragmented contents stimulates nearby cells to divide.
D) Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self-digests.
E) Its nucleus and organelles are lysed, then the cell enlarges and bursts.
B) activation of a developmental pathway found in the worm but not in humans
C) a form of cancer in which there is insufficient apoptosis
D) webbing of fingers or toes
E) excess skin exfoliation
A) Cell death would usually spread from one cell to the next via paracrine signals.
B) Lysosomal enzymes exiting the dying cell would damage surrounding cells.
C) Released cellular energy would interfere with the neighbors’ energy budget.
D) Bits of membrane from the dying cell could merge with neighbors and bring in foreign receptors.
E) Neighboring cells would activate immunological responses.
A) It prevents the caspase activity of ced-3 and ced-4.
B) Ced-9 remains inactive until it is signaled by ced-3 and other caspases.
C) Ced-9 cleaves to produce ced-3 and ced-4.
D) Ced-9 enters the nucleus and activates apoptotic genes.
E) Ced-9 prevents blebbing by its action on the cell membrane.
A) Growth factor ligands do not bind as efficiently to receptors.
B) Their lower hormone concentrations elicit a lesser response.
C) cAMP levels change very frequently.
D) Enzymatic activity declines.
E) ATP production decreases.
A) the nucleus only
B) the ER only
C) ligand binding only
D) mitochondrial protein leakage only
E) all of the above
A) an increase in the relative frequency of deaths from cancer
B) an increased need for gerontologists and other professionals to care for the elderly
C) an increase in the total population of humans on the planet
D) a decrease in the ratio of younger to older members of the population
E) a decrease in the birth rate
Which of the following types of signaling is represented in the figure?
E) long distance
In the figure, the dots in the space between the two structures represent which of the following?
A) receptor molecules
B) signal transducers
Where would you expect to find the carboxyl end?
A) at the exterior surface
B) at the cytosol surface
C) connected with the loop at H5 and H6
D) between the membrane layers
The coupled G protein most likely interacts with this receptor
A) at the NH₃ end.
B) at the COO- end.
C) along the exterior margin.
D) along the interior margin.
E) at the loop between H5 and H6.
If you wish to design an experiment to block the G protein-coupled receptor interaction, the block would preferentially affect which of the following?
A) the exterior (cytoplasmic) end of the receptor
B) the cytosolic end of the receptor
C) the phospholipid’s transmembrane domain
D) the amino acid sequence in the binding site for the G protein
E) the amino acids in the binding site for the transduction molecules
When an excess of the ligand (hormone) is poured through the column after the receptor binding step, what do you expect will occur?
A) The ligand will attach to those beads that have the receptor and remain on the column.
B) The ligand will cause the receptor to be displaced from the beads and eluted out.
C) The ligand will attach to the bead instead of the receptor.
D) The ligand will cause the bead to lose its affinity by changing shape.
E) The reaction will cause a pH change due to electron transfer.
This method of affinity chromatography would be expected to collect which of the following?
A) molecules of the hormone
B) molecules of purified receptor
C) G proteins
D) assorted membrane proteins
E) hormone-receptor complexes
The description above illustrates which of the following?
A) Just because a drug acts on one type of receptor does not mean that it will act on another type.
B) Beta blockers can be used effectively on any type of muscle.
C) Beta adrenergic receptors must be in the cytosol if they are going to influence contraction and relaxation.
D) The chemical structures of the beta 1 and beta 2 receptors must have the same active sites.
The use of beta 2 antagonist drugs may be useful in asthma because they may
A) increase constriction of the skeletal muscle of the chest wall.
B) increase heart rate and therefore allow the patient to get more oxygen circulated.
C) dilate the bronchioles by relaxing their smooth muscle.
D) override the beta blockers that the patient is already taking.
E) obstruct all G protein-mediated receptors.
Beta 2 antagonist drugs might also be used most effectively for which of the following?
A) cardiac arrhythmias
B) increased gastric acid production
C) neuropathy of the extremities
D) increasing low blood pressure
E) decreasing peristalsis
A) they are species specific.
B) they always lead to the same cellular response.
C) they amplify the original signal manyfold.
D) they counter the harmful effects of phosphatases.
E) the number of molecules used is small and fixed.
A) receptor tyrosine kinase
B) G protein-coupled receptor
C) phosphorylated receptor tyrosine kinase dimer
D) ligand-gated ion channel
E) intracellular receptor
A) dimerization and phosphorylation.
B) dimerization and IP3 binding.
C) a phosphorylation cascade.
D) GTP hydrolysis.
E) channel protein shape change.
A) only target cells retain the appropriate DNA segments.
B) intracellular receptors are present only in target cells.
C) most cells lack the Y chromosome required.
D) only target cells possess the cytosolic enzymes that transduce the testosterone.
E) only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor.
B) G protein
D) adenylyl cyclase
E) G protein-coupled receptor
A) fragmentation of the DNA
B) cell-signaling pathways
C) activation of cellular enzymes
D) lysis of the cell
E) digestion of cellular contents by scavenger cells
A) Enzymatic activity was proportional to the amount of calcium added to a cell-free extract.
B) Receptor studies indicated that epinephrine was a ligand.
C) Glycogen breakdown was observed only when epinephrine was administered to intact cells.
D) Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined.
E) Epinephrine was known to have different effects on different types of cells.
A) regulation of transcription by extracellular signaling molecules.
B) enzyme activation.
C) activation of G protein-coupled receptors.
D) activation of receptor tyrosine kinases.
E) activation of protein kinase molecules.