AP Biology Chapter 11-13 Test Review

What is the most probable hypothesis about these intermediate forms of cell division? A) They represent a form of cell reproduction which must have evolved completely separately from those of other organisms. B) They demonstrate that these species are not closely related to any of the other protists and may well be a different kingdom. C) They rely on totally different proteins for the processes they undergo. D) They may be more closely related to plant forms that also have unusual mitosis. E) They represent existing species that have retained from an ancestral species some of the evolutionary steps toward complete mitosis.

A) They represent a form of cell reproduction which must have evolved completely separately from those of other organisms.

Use the following information to answer the questions below. A student is looking through his light microscope (~450 X) at a squashed and stained onion root tip. Some, but not all, of the cells have clearly visible chromosome strands. When a cell is in anaphase of mitosis, which of the following will he see? A) a clear area in the center of the cell B) chromosomes clustered at the poles C) individual chromatids separating D) chromosomes clustered tightly at the center E) formation of vesicles at the midline

A) a clear area in the center of the cell

The MPF protein complex turns itself off by A) activating a process that destroys cyclin components. B) activating an enzyme that stimulates cyclin. C) binding to chromatin. D) exiting the cell. E) activating the anaphase-promoting complex.

A) activating a process that destroys cyclin components.

In general, a signal transmitted via phosphorylation of a series of proteins 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) brings a conformational change to each protein.

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger. A) cAMP B) G protein C) GTP D) adenylyl cyclase E) G protein-coupled receptor

A) cAMP

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in A) cells with more than one nucleus. B) cells that are unusually small. C) cells lacking nuclei. D) destruction of chromosomes. E) cell cycles lacking an S phase.

A) cells with more than one nucleus.

The centromere is a region in which A) chromatids remain attached to one another until anaphase. B) metaphase chromosomes become aligned at the metaphase plate. C) chromosomes are grouped during telophase. D) the nucleus is located prior to mitosis. E) new spindle microtubules form at either end.

A) chromatids remain attached to one another until anaphase.

The activation of receptor tyrosine kinases is characterized by A) dimerization and phosphorylation. B) dimerization and IP3 binding. C) a phosphorylation cascade. D) GTP hydrolysis. E) channel protein shape change.

A) dimerization and phosphorylation.

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to A) disruption of mitotic spindle formation. B) inhibition of regulatory protein phosphorylation. C) suppression of cyclin production. D) myosin denaturation and inhibition of cleavage furrow formation. E) inhibition of DNA synthesis.

A) disruption of mitotic spindle formation.

Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting the A) hydrolysis of cGMP to GMP. B) hydrolysis of GTP to GDP. C) phosphorylation of GDP. D) dephosphorylation of cGMP. E) removal of GMP from the cell.

A) hydrolysis of cGMP to GMP.

The toxin of Vibrio cholerae causes profuse diarrhea because it 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) modifies a G protein involved in regulating salt and water secretion.

You have the technology necessary to measure each of the following in a sample of animal cells: chlorophylls, organelle density, picograms of DNA, cell wall components, and enzymatic activity. Which would you expect to increase significantly from M to G1? A) organelle density and enzymatic activity B) cell wall components and DNA C) chlorophyll and cell walls D) organelle density and cell walls E) chlorophyll and DNA

A) organelle density and enzymatic activity

During which phase of mitosis do the chromatids become chromosomes? A) telophase B) anaphase C) prophase D) metaphase E) cytokinesis

A) telophase

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, Taxol must affect A) the formation of the mitotic spindle. B) anaphase. C) formation of the centrioles. D) chromatid assembly. E) the S phase of the cell cycle.

A) the formation of the mitotic spindle.

Using the yeast signal transduction pathways, both types of mating cells release the mating factors. These factors bind to specific receptors on the correct cells, 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) which induce changes in the cells that lead to cell fusion.

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

B) Plant hormones may travel in air or through vascular systems.

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because 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) intracellular receptors are present only in target cells.

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

B) molecules of purified receptor

Which of the following does not occur during mitosis? A) condensation of the chromosomes B) replication of the DNA C) separation of sister chromatids D) spindle formation E) separation of the spindle poles

B) replication of the DNA

Anchorage dependence of animal cells in vitro or in vivo depends on which of the following? A) attachment of spindle fibers to centrioles B) response of the cell cycle controls to signals from the plasma membrane C) the absence of an extracellular matrix D) the absence of cell-surface phospholipids to those of adjoining cells E) the binding of cell-surface phospholipids to the substrate

B) response of the cell cycle controls to signals from the plasma membrane

Why do chromosomes coil during mitosis? A) to increase their potential energy B) to allow the chromosomes to move without becoming entangled and breaking C) to allow the chromosomes to fit within the nuclear envelope D) to allow the sister chromatids to remain attached E) to provide for the structure of the centromere

B) to allow the chromosomes to move without becoming entangled and breaking

For anaphase to begin, which of the following must occur? A) Chromatids must lose their kinetochores. B) Cohesin must attach the sister chromatids to each other. C) Cohesin must be cleaved enzymatically. D) Kinetochores must attach to the metaphase plate. E) Spindle microtubules must begin to depolymerize.

C) Cohesin must be cleaved enzymatically.

Which of the following is a correct association? 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

C) GTPase activity and hydrolysis of GTP to GDP

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

C) Glycogen breakdown was observed only when epinephrine was administered to intact cells.

You have a series of cells, all of which were derived from tumors, and you first need to find out which ones are malignant. What could you do? A) See which ones are not overproliferating. B) Find out which ones have a higher rate of apoptosis. C) Karyotype samples to look for unusual size and number of chromosomes. D) Measure metastasis. E) Time their cell cycles.

C) Karyotype samples to look for unusual size and number of chromosomes.

A particular cyclin called cyclin E forms a complex with Cdk 2 (cyclin-dependent kinase 2). This complex is important for the progression of the cell from G1 into the S phase of the cell cycle. Which of the following statements is correct? A) The amount of free cyclin E is greatest during the S phase. B) The amount of free Cdk 2 is greater during G1 compared to the S phase. C) The amount of free cyclin E is highest during G1. D) The amount of free Cdk 2 is greatest during G1. E) The activity of the cyclin E/Cdk 2 complex is highest during G2.

C) The amount of free cyclin E is highest during G₁.

A plant-derived protein known as colchicine can be used to poison cells by blocking the formation of the spindle. Which of the following would result if colchicine is added to a sample of cells in G2? A) The cells would immediately die. B) The cells would be unable to begin M and stay in G2. C) The chromosomes would coil and shorten but have no spindle to which to attach. D) The chromosomes would segregate but in a disorderly pattern. E) Each resultant daughter cell would also be unable to form a spindle.

C) The chromosomes would coil and shorten but have no spindle to which to attach.

Why do neurons and some other specialized cells divide infrequently? A) They no longer have active nuclei. B) They no longer carry receptors for signal molecules. C) They have been shunted into G0. D) They can no longer bind Cdk to cyclin. E) They show a drop in MPF concentration.

C) They have been shunted into G₀.

Which of the following is a likely explanation of why natural selection favored the evolution of signals for sexual reproduction? 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) Even in the simplest organisms, sexual reproduction required several coordinated responses by cells.

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling? 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) Growth factor ligands do not bind as efficiently to receptors.

In C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways? 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) It prevents the caspase activity of ced-3 and ced-4.

Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP? 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) It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

Which of the following is released by platelets in the vicinity of an injury? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk

A) PDGF

At the M phase checkpoint, the complex allows for what to occur? A) Separase enzyme cleaves cohesins and allows chromatids to separate. B) Cohesins alter separase to allow chromatids to separate. C) Kinetochores are able to bind to spindle microtubules. D) All microtubules are made to bind to kinetochores. E) Daughter cells are allowed to pass into G1.

A) Separase enzyme cleaves cohesins and allows chromatids to separate.

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

C) aggregation of bacteria that can cause cavities

The human population's life expectancy has increased significantly but seems to have an upper limit. Which of the following might be described as an ecological consequence of passing that upper limit by regulating cell death? 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

C) an increase in the total population of humans on the planet

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of A) phosphorylated proteins. B) GTP. C) cAMP. D) adenylyl cyclase. E) activated G proteins.

C) cAMP.

One difference between cancer cells and normal cells is that cancer cells A) are unable to synthesize DNA. B) are arrested at the S phase of the cell cycle. C) continue to divide even when they are tightly packed together. D) cannot function properly because they are affected by density -dependent inhibition. E) are always in the M phase of the cell cycle.

C) continue to divide even when they are tightly packed together.

GTPase activity is involved in the regulation of signal transduction because it A) increases the available concentration of phosphate. B) decreases the amount of G protein in the membrane. C) hydrolyzes GTP to GDP. D) converts cGMP to GTP. E) phosphorylates protein kinases.

C) hydrolyzes GTP binding to G protein.

Which of the following most accurately describes a cyclin? A) It is present in similar concentrations throughout the cell cycle. B) It is activated to phosphorylate by complexing with a Cdk. C) It decreases in concentration when MPF activity increases. D) It activates a Cdk molecule when it is in sufficient concentration. E) It activates a Cdk when its concentration is decreased.

D) It activates a Cdk molecule when it is in sufficient concentration.

Which of the following is a protein maintained at constant levels throughout the cell cycle that requires cyclin to become catalytically active? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk

D) cyclin

In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis? A) seedless plants B) dinoflagellates C) diatoms D) dinoflagellates and diatoms only E) seedless plants, dinoflagellates, and diatoms

D) dinoflagellates and diatoms only

The termination phase of cell signaling requires which of the following? A) removal of the receptor B) activation of a different set of relay molecules C) converting ATP to cAMP D) dissociation of the signaling molecule from the receptor E) apoptosis

D) dissociation of the signaling molecule from the receptor

What causes the decrease in the amount of cyclin at a specific point in the cell cycle? A) an increase in production once the restriction point is passed B) the cascade of increased production once its protein is phosphorylated by Cdk C) the changing ratio of cytoplasm to genome D) its destruction by a process initiated by the activity of its complex with a cyclin E) the binding of PDGF to receptors on the cell surface

D) its destruction by a process initiated by the activity of its complex with a cyclin

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane? A) receptor tyrosine kinase B) G protein-coupled receptor C) phosphorylated receptor tyrosine kinase dimer D) ligand-gated ion channel E) intracellular receptor

D) ligand-gated ion channel

Apoptosis involves all but which of the following? 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

D) lysis of the cell

Which of the following is a function of those spindle microtubules that do not attach to kinetochores? A) maintaining an appropriate spacing among the moving chromosomes B) producing a cleavage furrow when telophase is complete C) providing the ATP needed by the fibers attached to kinetochores D) maintaining the region of overlap of microtubules in the cell's center E) pulling the poles of the spindles closer to one another

D) maintaining the region of overlap of microtubules in the cell's center

If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the spindle apparatus, at which stage will mitosis be arrested? A) anaphase B) prophase C) telophase D) metaphase E) interphase

D) metaphase

Which of the following describes the events of apoptosis? A) The cell dies, it is lysed, its organelles are phagocytized, and its contents are recycled. B) The cell's DNA and organelles become fragmented, the cell dies, and it is phagocytized. C) The cell dies, and the presence of its fragmented contents stimulates nearby cells to divide. D) The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells. E) The cell's nucleus and organelles are lysed, and the cell enlarges and bursts.

D) The cell's DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell's parts are packaged in vesicles that are digested by specialized cells.

A research team began a study of a cultured cell line. Their preliminary observations showed them that the cell line did not exhibit either density-dependent inhibition or anchorage dependence. What could they conclude right away? A) The cells originated in the nervous system. B) The cells are unable to form spindle microtubules. C) They have altered series of cell cycle phases. D) The cells show characteristics of tumors. E) They were originally derived from an elderly organism.

D) The cells show characteristics of tumors.

An inhibitor of phosphodiesterase activity would have which of the following effects? 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

D) prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm

Using which of the following techniques would enable your lab group to distinguish between a cell in G2 and a cell from the same organism in G1? A) fluorescence microscopy B) electron microscopy C) spectrophotometry D) radioactive-labeled nucleotides E) labeled kinetochore proteins

D) radioactive-labeled nucleotides

The receptors for a group of signaling molecules known as growth factors are often A) ligand-gated ion channels. B) G protein-coupled receptors. C) cyclic AMP. D) receptor tyrosine kinases. E) neurotransmitters.

D) receptor tyrosine kinases.

Movement of the chromosomes during anaphase would be most affected by a drug that prevents A) nuclear envelope breakdown. B) cell wall formation. C) elongation of microtubules. D) shortening of microtubules. E) formation of a cleavage furrow.

D) shortening of microtubules.

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway? A) receptor B) relay molecule C) transducer D) signal molecule E) endocrine molecule

D) signal molecule

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound 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.

D) that increases phosphodiesterase activity.

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

D) the amino acid sequence in the binding site for the G protein

Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic (animal) nucleus. It might consist of which of the following? A) one-twelfth of the genes of the organism B) two chromosomes, each with six chromatids C) a single circular piece of DNA D) two long strands of DNA plus proteins E) two chromatids attached together at a centromere

D) two long strands of DNA plus proteins

Which of the following describe(s) cyclin-dependent kinase (Cdk)? A) Cdk is inactive, or "turned off," in the presence of cyclin. B) Cdk is present throughout the cell cycle. C) Cdk is an enzyme that attaches phosphate groups to other proteins. D) Cdk is inactive, or "turned off," in the presence of cyclin and it is present throughout the cell cycle. E) Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins.

E) Cdk is present throughout the cell cycle and is an enzyme that attaches phosphate groups to other proteins.

For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable? A) It is safe enough to limit all apoptosis. B) It does not alter metabolically active cells. C) It only attacks cells that are density dependent. D) It interferes with cells entering G0. E) It interferes with rapidly dividing cells.

E) It interferes with rapidly dividing cells.

The cyclin component of MPF is destroyed toward the end of which phase? A) G0 B) G1 C) S D) G2 E) M

E) M

Which of the following is true of transcription factors? 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.

D) They control gene expression.

The following information applies to the questions below. Several organisms, primarily protists, have what are called intermediate mitotic organization These protists are intermediate in what sense? A) They reproduce by binary fission in their early stages of development and by mitosis when they are mature. B) They never coil up their chromosomes when they are dividing. C) They use mitotic division but only have circular chromosomes. D) They maintain a nuclear envelope during division. E) None of them form spindles.

D) They maintain a nuclear envelope during division.

What is most likely to happen to an animal's target cells that lack receptors for local regulators? 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.

D) They might not be able to multiply in response to growth factors from nearby cells.

Which of the following proteins are involved in binary fission as well as eukaryotic mitotic division? A) cyclins B) Cdks C) MPF D) actin and tubulin E) cohesins

D) actin and tubulin

The function of phosphatases in signal transduction is best described as to 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.

E) inactivate protein kinases and turn off the signal transduction.

At which phase are centrioles beginning to move apart in animal cells? A) telophase B) anaphase C) prometaphase D) metaphase E) prophase

E) prophase

When the cell has just completed telophase, which of the following will he see? A) a clear area in the center of the cell B) chromosomes clustered at the poles C) individual chromatids separating D) breakdown of the nuclear envelope E) two small cells with chromatin

E) two small cells with chromatin

If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis? A) 10 B) 20 C) 30 D) 40 E) 80

A) 10

If there are 20 chromatids in a cell, how many centromeres are there? A) 10 B) 20 C) 30 D) 40 E) 80

A) 10

Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells? A) kinetochores B) Golgi-derived vesicles C) actin and myosin D) centrioles and centromeres E) tubulin and dynein

B) Golgi-derived vesicles

After which checkpoint is the cell first committed to continue the cell cycle through M? A) G0 B) G1 C) G2 D) S E) previous M

B) G₁

Which of the following triggers the cell's passage past the G2 checkpoint into mitosis? A) PDGF B) MPF C) protein kinase D) cyclin E) Cdk

B) MPF

Use this information to answer the following questions. Affinity chromatography is a method that can be used to purify cell-surface receptors, while they retain their hormone-binding ability. A ligand (hormone) for a receptor of interest is chemically linked to polystyrene beads. A solubilized preparation of membrane proteins is passed over a column containing these beads. Only the receptor binds to the beads. 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 removed from the column. 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.

B) The ligand will cause the receptor to be displaced from the beads and eluted out.

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

B) The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.

Since steroid receptors are located intracellularly, which of the following is true? 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.

B) The steroid/receptor complex can cross the nuclear membrane.

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely A) an animal cell in the process of cytokinesis. B) a plant cell in the process of cytokinesis. C) an animal cell in the S phase of the cell cycle. D) a bacterial cell dividing. E) a plant cell in metaphase.

B) a plant cell in the process of cytokinesis.

In which of the following ways could signal transduction most probably be explored in research to treat cancer? 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

B) alteration of protein kinases in cell cycle regulation in order to slow cancer growth

Use this description to answer the following questions. A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others. 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

B) at the cytosol surface

Testosterone functions inside a cell by 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 nitric oxide. E) coordinating a phosphorylation cascade that increases spermatogenesis.

B) binding with a receptor protein that enters the nucleus and activates specific genes.

Where do the microtubules of the spindle originate during mitosis in animal cells? A) centromere B) centrosome C) centriole D) chromatid E) kinetochore

B) centrosome

Which of the following is the best explanation for the inability of a specific animal cell to reduce the Ca2+ concentration in its cytosol compared with the extracellular fluid? 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

C) insufficient ATP levels in the cytoplasm

Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor? A) enhanced anchorage dependence B) changes in the order of cell cycle stages C) lack of appropriate cell death D) inability to form spindles E) inability of chromosomes to meet at the metaphase plate

C) lack of appropriate cell death

What are scaffolding proteins? 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

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

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding? A) hormonal signaling B) autocrine signaling C) paracrine signaling D) endocrine signaling E) synaptic signaling

C) paracrine signaling

Adenylyl cyclase has the opposite effect of which of the following? A) protein kinase B) protein phosphatase C) phosphodiesterase D) phosphorylase E) GTPase

C) phosphodiesterase

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction? A) tyrosines B) glycine and histidine C) serine and threonine D) glycine and glutamic acid E) Any of the 20 amino acids are equally phosphorylated.

C) serine and threonine

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because 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.

C) they amplify the original signal manyfold.

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound 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.

C) to block G protein activity in liver cells.

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells? A) 4 B) 8 C) 16 D) 32 E) 64

D) 32

Which of the following is (are) required for motor proteins to function in the movement of chromosomes toward the poles of the mitotic spindle? A) intact centromeres B) an MTOC (microtubule organizing center) C) a kinetochore attached to the metaphase plate D) ATP as an energy source E) synthesis of cohesin

D) ATP as an energy source

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

D) Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.

Which of the following statements is true of signaling molecules? A) When signaling 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, signaling 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 signaling molecule. E) Protein kinase A activation is one possible result of signaling molecules binding to G protein-coupled receptors.

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

All cell cycle checkpoints are similar in which way? A) They respond to the same cyclins. B) They utilize the same Cdks. C) They give the go-ahead signal to progress to the next checkpoint. D) They each have only one cyclin/Cdk complex. E) They activate or inactivate other proteins.

E) They activate or inactivate other proteins.

Because most receptors are membrane proteins, which of the following is usually true? 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.

E) They change their conformation after binding with signal polypeptides.

Which of the following is true concerning cancer cells? A) They do not exhibit density-dependent inhibition when growing in culture. B) When they stop dividing, they do so at random points in the cell cycle. C) They are not subject to cell cycle controls. D) When they stop dividing, they do so at random points in the cell cycle, and they are not subject to cell cycle controls. E) When they stop dividing, they do so at random points in the cell cycle; they are not subject to cell cycle controls; and they do not exhibit density-dependent inhibition when growing in culture.

E) When they stop dividing, they do so at random points in the cell cycle; they are not subject to cell cycle controls; and they do not exhibit density-dependent inhibition when growing in culture.

Where do apoptotic signals come from? A) the nucleus only B) the ER only C) ligand binding only D) mitochondrial protein leakage only E) all of the above

E) all of the above

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.

E) at the loop between H5 and H6.

Proteins that are involved in the regulation of the cell cycle, and that show fluctuations in concentration during the cell cycle, are called A) ATPases. B) kinetochores. C) kinases. D) estrogen receptors. E) cyclins.

E) cyclins.

Sutherland discovered that epinephrine signals 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.

E) elevation of cytosolic concentrations of cyclic AMP.