Cell Bio HW #8/#9/#10
Which of the answer choices would be found in the cytoplasm and not on the cell surface? A. A receptor that binds a nonpolar steroid hormone and activates transcription B. A receptor that causes GDP to be exchanged for GTP in a G protein C. A receptor that allows ions to enter the cell when a ligand binds D. A receptor that must form a dimer after binding the ligand to transmit a signal
A. A receptor that binds a nonpolar steroid hormone and activates transcription
What protein forms the contractile ring during cytokinesis in animal cells? A. Actin B. Kinesin C. Dynein D. DNA polymerase
A. Actin
You are interested in cell-size regulation and discover that signaling through a GCPR called ERC1 is important in controlling cell size in embryonic rat cells. The G-protein downstream of ERC1 activates Adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version PKA are 15% larger than normal cells. Given these results, which of the following statements to embryonic rat cells should lead to smaller cells? A. Addition of a drug that causes cyclic AMP Phosphodiesterase to be hyperactive B. Addition of a drug that prevents GTP hydrolysis by Gα C. Addition of a drug that activates Adenylyl cyclase D. Addition of a drug that mimics the ligand of ERC1
A. Addition of a drug that causes cyclic AMP Phosphodiesterase to be hyperactive
Which of the events are listed in the correct order of G protein-coupled signaling? A. Adenylyl cyclase catalyzes the formation of cAMP, which activates protein kinase A (PKA). B. Protein kinase A (PKA) phosphorylates adenylyl cyclase, which then synthesizes cAMP from ATP. C. cAMP activates adenylyl cyclase, which activates protein kinase A (PKA).
A. Adenylyl cyclase catalyzes the formation of cAMP, which activates protein kinase A (PKA).
A cellular response to a signal can be terminated by: A. All of these choices are correct. B. inactivation of proteins in the signal pathway over time. C. inactivation of intracellular signal transduction proteins. D. depletion of a second messenger. E. depletion of the signal that activates the receptor.
A. All of these choices are correct.
Which types of cellular activities can be a response to cell signaling? A. All of these choices are correct. B. Enzyme activities are changed. C. Cell signals are released to communicate with other cells. D. Gene expression patterns are changed. E. Cell division is triggered.
A. All of these choices are correct.
Which of the following statements is FALSE? A. Cdc 25 dephosphorylation of Wee1 activates the kinase (CAK), promoting the G2/M transition. B. Phosphorylation of mitotic Cdk by the inhibitory kinase (Wee1) makes the Cdk inactive. C. Inhibiting the Cdc 25 phosphatase will delay the G2/M transition. D. The activating phosphatase (Cdc 25) removes the phosphates from mitotic Cdk that were added by Wee1 so that M-Cdk complex will be active.
A. Cdc 25 dephosphorylation of Wee1 activates the kinase (CAK), promoting the G2/M transition.
What is the result of DNA ligase's activity? A. DNA fragments are joined together B. DNA is broken up at specific sites C. DNA translation occurs D. DNA transcription occurs E. DNA is condensed into chromosomes
A. DNA fragments are joined together
Which of the following statements is TRUE? A. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. B. To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. C. A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response. D. Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type.
A. Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.
Normally, when adrenaline binds to adrenergic G-protein coupled receptors on the surface of a muscle cell, it activates a G protein, initiating an intracellular signaling pathway in which the activated α subunit activates Adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. How would glycogen levels be affected in the presence of adrenaline in abnormal cells that lack fully functional Adenylyl cyclase? A. Glycogen levels would be higher than in normal cells treated with adrenaline B. Glycogen levels would be lower than in normal cells treated with adrenaline C. Glycogen levels would be about the same as normal cells treated with adrenaline
A. Glycogen levels would be higher than in normal cells treated with adrenaline
Normally, when adrenaline binds to adrenergic G-protein coupled receptors on the surface of a muscle cell, it activates a G-protein, initiating an intracellular signaling pathway in which the activated α subunit activated Adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowing glycogen levels. How would glycogen levels be affected in the presence of adrenaline in abnormal cells in which of the subunit of the G-protein has a 100-fold higher affinity for GDP? A. Glycogen levels would be higher than in normal cells treated with adrenaline B. Glycogen levels would be lower than in normal cells treated with adrenaline C. Glycogen levels would be about the same as normal cells treated with adrenaline
A. Glycogen levels would be higher than in normal cells treated with adrenaline
Normally, when adrenaline binds to adrenergic G-protein coupled receptors on the surface of a muscle cell, it activates a G-protein, initiating an intracellular signaling pathway in which the activated α subunit activates Adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. How would glycogen levels be affected in the presence of adrenaline in abnormal cells that lack the G-protein coupled adrenaline receptor? A. Glycogen levels would be higher than in normal cells treated with adrenaline B. Glycogen levels would be lower than in normal cells treated with adrenaline C. Glycogen levels would be about the same as normal cells treated with adrenaline
A. Glycogen levels would be higher than in normal cells treated with adrenaline
Which enzyme moves outward from the origin of replication and breaks hydrogen bonds between DNA nucleotides? A. Helicase B. RNA polymerase C. Topoisomerase II D. DNA polymerase
A. Helicase
The following enzymes play an important role in DNA replication: DNA polymerase, primase, ligase, and helicase. In what order do they work during replication? A. Helicase, primase, DNA polymerase, ligase B. Primase, helicase, ligase, DNA polymerase C. DNA polymerase, helicase, primase, ligase D. DNA polymerase, primase, ligase, helicase E. Ligase, helicase, DNA polymerase, primase
A. Helicase, primase, DNA polymerase, ligase
In cell communication, which of these is a requirement of the responding cell? A. It must express receptor proteins. B. It must be a prokaryotic cell. C. It must be a eukaryotic cell. D. It must produce signaling molecules.
A. It must express receptor proteins.
When a nucleotide is added to a growing nucleic acid strand during DNA replication, the incoming monomer is __________, and the energy required to drive the polymerization is derived from __________. A. Nucleoside triphosphate; cleaving a pyrophosphate B. A nucleoside monophosphate; cleaving ATP C. An RNA primer; cleaving a pyrophosphate D. A nucleoside triphosphate; DNA polymerase
A. Nucleoside triphosphate; cleaving a pyrophosphate
Which of the following correctly describes a chromosome in G2 of the mitotic cell division cycle? A. One replicated chromosome, each consisting of two sister chromatids. B. One replicated chromosome consisting of two single-stranded DNA molecules C. Two replicated chromosomes, each consisting of two sister chromatids. D. Two replicated chromosomes, each consisting of two single-stranded DNA molecules
A. One replicated chromosome, each consisting of two sister chromatids.
The point at which DNA synthesis is initiated is called the: A. Origin of replication B. Primate C. Start codon D. Replication fork E. Primer
A. Origin of replication
You are doing an experiment on a new class of G protein-coupled receptor. You make several cell lines that each express the receptor, the corresponding G protein, and adenylyl cyclase. Each cell line has different mutations in these components. You decide to measure cyclic AMP (cAMP) in the cells of each cell line to understand the effect of each of these mutations. In one cell line, a mutation in the G protein-coupled receptor prevents it from binding to the G protein. Therefore, which of these would happen? A. The amount of cAMP in cells will decrease compared to cells with no mutations in the signaling pathway. B. The amount of cAMP in cells will be the same compared to cells with no mutations in the signaling pathway. C. The amount of cAMP in cells will increase compared to cells with no mutations in the signaling pathway.
A. The amount of cAMP in cells will decrease compared to cells with no mutations in the signaling pathway.
When RAS is activated, cells will divide. A dysfunction form of RAS clings too tightly to GDP. You introduce the dysfunctional form of RAS into cells that also have a normal version of RAS. Which of the following statements is true? A. The cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate RAS B. The cells you create will run out of the GTP necessary to activate RAS C. The cells you create will divide more frequently compared to normal cells in response to the extra cellular signals that typically activate RAS D. The normal RAS in the cells you create will not be able to bind GDP because the dominant-negative RAS binds to GDP too tightly
A. The cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate RAS
In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? A. At the transition between G1 and S B. When cells enter G0 C. During M D. At the end of G2
D. At the end of G2
Refer to Figure 16.23 Activated protein kinase C (PKC) can lead to the modification of the membrane lipids in the vicinity of the active PKC. Figure 16-17 shows how G proteins can indirectly activate PKC. You have discovered the enzyme activated by PKC that mediates the lipid modification. You call the enzyme Rafty and demonstrate that activated PKC directly phosphorylates Rafty, activating it to modify the plasma membrane lipids in the vicinity of the cell where PKC is active; these lipid modifications can be detected by dyes that bind to the modified lipids. Cells lacking Rafty do not have these modifications, even when PKC is active. Which of the following conditions would lead to signal-independent modification of the membrane lipids by Rafty? A. The expression of a constitutively active phospholipase C B. A mutation in the GPCR that binds the signal more tightly C. A Ca2+ channel in the endoplasmic reticulum with an increased affinity for IP3 D. A mutation in the gene that encodes Rafty such that the enzyme can no longer be phosphorylated by PKC
A. The expression of a constitutively active phospholipase C
Okazaki fragments are found on ____________ strand of DNA. A. The lagging B. The leading C. The parental D. Both leading and lagging
A. The lagging
The centromere is: A. The microtubule organizing center for the mitotic spindle B. A region of the chromosome where kinetochores attach C. A region of the chromosome where microtubules attach to chromosomes during mitosis D. A region of the chromosome where sister chromatids are attached to each other
A. The microtubule organizing center for the mitotic spindle
What is the function of the centromere? A. To attach the sister chromatids to each other B. To attach the chromosome to the spindle C. to attach the DNA to the plasma membrane D. To organize the microtubules to form a spindle
A. To attach the sister chromatids to each other
Which answer option correctly lists the types of cellular communication from shortest to longest distance traveled by the signaling molecule to reach its responding cell? A. autocrine, paracrine, endocrine B. endocrine, paracrine, autocrine C. paracrine, autocrine, endocrine D. autocrine, endocrine, paracrine
A. autocrine, paracrine, endocrine
An increased heart rate caused by the release of adrenaline from the adrenal glands, which are located just above the kidney, is an example of _____ signaling. A. endocrine B. autocrine C. contact-dependent D. paracrine
A. endocrine
Communication between neurons is an example of which type of cell signaling? A. paracrine signaling B. contact-dependent signaling C. endocrine signaling D. autocrine signaling
A. paracrine signaling
Which is the correct order for these steps in cell signaling? A. receptor activation, signal transduction, response B. receptor activation, response, signal transduction C. signal transduction, receptor activation, response D. response, signal transduction, termination
A. receptor activation, signal transduction, response
How many replication forks are formed when an origin of replication is opened? A. 1 B. 2 C. 3 D. 4
B. 2
The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization? A. A mutation that increases the affinity of RGFR for RGF B. A mutation that prevents RGFR from binding to RGF C. Changing the tyrosine's that are normally phosphorylated on RGFR dimerization to alanine's D. Changing the tyrosine's that are normally phosphorylated on RGFR dimerization to glutamic acid
B. A mutation that prevents RGFR from binding to RGF
The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization? A. A mutation that increases the affinity of RGFR for RGF B. A mutation that prevents RGFR from binding to RGF C. Changing the tyrosines that are normally phosphorylated on RGFR dimerization to alanines D. Changing on the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid
B. A mutation that prevents RGFR from binding to RGF
Normally, when adrenaline binds to adrenergic G-protein coupled receptors on the surface of a muscle cell, it activates a G-protein, initiating an intracellular signaling pathway in which the activated α subunit activates Adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. How would glycogen levels be affected in the presence of adrenaline in abnormal cells that lack cAMP Phosphodiesterase? A. Glycogen levels would be higher than in normal cells treated with adrenaline B. Glycogen levels would be lower than in normal cells treated with adrenaline C. Glycogen levels would be about the same as normal cells treated with adrenaline
B. Glycogen levels would be lower than in normal cells treated with adrenaline
Which of the following statements is true? A. MAP kinase is most important for phosphorylating MAP kinase kinase B. PI-3 kinase phosphorylated a lipid in the plasma membrane C. RAS becomes activated when an RTK phosphorylates its bound GDP to create GTP D. Dimerization of GPCR's leads to Gα activation
B. PI-3 kinase phosphorylated a lipid in the plasma membrane
Progression through the cell cycle requires a cyclin to bind to a CDK because... A. The cyclin are the molecules with the enzymatic activity in the complex B. The binding of a cyclic to CDK is required for CDK enzymatic activity C. Cyclic binding inhibits CDK activity until the appropriate time in the cell cycle D. Without cyclin binding, a cell-cycle checkpoint will be activated
B. The binding of a cyclin to CDK is required for CDK enzymatic activity
Which of the following events does not usually occur during interphase? A. Cells grow in size B. The nuclear envelope breaks down C. DNA is replicated D. The centromeres are duplicated
B. The nuclear envelope breaks down
Many scientists use chemical inhibitors to interfere with normal signaling pathways within eukaryotic cells. If such inhibitors are large polar molecules, what is the likely method of action of these chemical inhibitors? A. These chemical inhibitors likely function in the cytoplasm, where they interfere with the termination of signaling, so eukaryotic cells can't process new signals. B. These chemical inhibitors likely bind to receptors on the cell surface and interfere with receptor activation or signal-receptor binding. C. These chemical inhibitors likely enter the nucleus and prevent the transcription of the pathway of interest's target genes. D. These chemical inhibitors likely enter eukaryotic cells and interfere with components of the signal transduction pathway.
B. These chemical inhibitors likely bind to receptors on the cell surface and interfere with receptor activation or signal-receptor binding
What is the function of the kinetochores? A. To attach the sister chromatids to each other B. To attach the chromosome to the spindle C. To attach the DNA to the plasma membrane D. To organize the microtubules to form a spindle
B. To attach the chromosome to the spindle
Which of the answer choices would be found in the cytoplasm and not on the cell surface? A. a receptor that causes GDP to be exchanged for GTP in a G protein B. a receptor that binds a nonpolar steroid hormone and activates transcription C. a receptor that allows ions to enter the cell when a ligand binds D. a receptor that must form a dimer after binding the ligand to transmit a signal
B. a receptor that binds a nonpolar steroid hormone and activates transcription
At the end of DNA replication, the sister chromatids are held together by the A. Kinetochores B. Securins C. Cohesins D. Histones
C. Cohesins
*Graph is depicted. Cells growing in culture were treated with a growth factor and were monitored as they progressed through the cell cycle. The amounts of cyclin B, CDK1 and DNA polymerase III activity were measured. Based on what you know about the different phases of the cell cycle and its regulation by cyclins and CDKs, answer the following three questions using the information in the graph to the right. Which of the curves in the graph represents the amount of cyclin B? A. Curve A B. Curve B C. Curve C D. None of the curves represent this.
C. Curve C
DNA replication is considered semi conservative because... A. After many rounds of DNA replication, the original DNA double helix is still intact B. Each new daughter DNA molecule consists of two new strands copied from the parent DNA molecule C. Each new daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand D. New DNA strands must be copied from a DNA template
C. Each new daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand
The concentration of mitotic cyclin (M cyclin) A. Rises markedly during M phase. B. Is activated by phosphorylation. C. Falls toward the end of M phase as a result of ubiquitylation and degradation. D. Is highest in G1 phase.
C. Falls toward the end of M phase as a result of ubiquitylation and degradation.
The process of DNA replication requires that each of the parental DNA strands be used as a __________ to produce a duplicate of the opposing strand. A. Catalyst B. Competitor C. Template D. Copy
C. Template
You are doing an experiment on a new class of G protein-coupled receptor. You make several cell lines that each express the receptor, the corresponding G protein, and adenylyl cyclase. Each cell line has different mutations in these components. You decide to measure cyclic AMP (cAMP) in the cells of each cell line to understand the effect of each of these mutations. In one cell lines, a mutation in the alpha subunit of the G protein prevents the release of bound GDP when the receptor is activated by its ligand. Therefore, which of these would happen? A. The amount of cAMP in cells will be the same compared to cells with no mutations in the signaling pathway. B. The amount of cAMP in cells will increase compared to cells with no mutations in the signaling pathway. C. The amount of cAMP in cells will decrease compared to cells with no mutations in the signaling pathway.
C. The amount of cAMP in cells will decrease compared to cells with no mutations in the signaling pathway.
What causes the deactivation of a G protein? A. The inactive receptor catalyzes the replacement of GTP by GDP. B. A phosphatase removes the inorganic phosphate group from GTP. C. The α (alpha) subunit catalyzes the hydrolysis of GTP to GDP and inorganic phosphate. D. The β (beta) and γ (gamma) subunits trigger the hydrolysis of GTP to GDP.
C. The α (alpha) subunit catalyzes the hydrolysis of GTP to GDP and inorganic phosphate.
The signaling molecule involved in contact-dependent cell signaling must be: A. a small soluble peptide. B. a neurotransmitter. C. a transmembrane protein. D. a growth factor.
C. a transmembrane protein.
Refer to Figure 16.21. Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen, as depicted in Figure 16-16. Which of the following statements is FALSE? A. A constitutively active mutant form of PKA in skeletal muscle cells would lead to a decrease in the amount of unphosphorylated phosphorylase kinase. B. A constitutively active mutant form of PKA in skeletal muscle cells would not increase the affinity of adrenaline for the adrenergic receptor. C. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glucose available. D. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.
D. A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.
During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in __________signaling. A. Endocrine B. Paracrine C. Neuronal D. Contact-dependent (juxtacrine)
D. Contact-dependent (juxtacrine) Pg. 565
Levels of Cdk activity change during the cell cycle, in part because A. the Cdks phosphorylate each other. B. The Cdks activate the cyclins. C. Cdk degradation precedes entry into the next phase of the cell cycle. D. Cyclin activity change during the cycle.
D. Cyclin activity change during the cycle.
Levels of CDK activity change during the cell cycle, in part because... A. The CDK's phosphorylate each other B. The CDK's activate the cyclins C. CDK degradation precedes entry into the next phase of the cell cycle D. Cyclin levels change during the cycle
D. Cyclin levels change during the cycle
Which diagram accurately represents the directionality of DNA strands at one side of a replication fork? A. Diagram A B. Diagram B C. Diagram C D. Diagram D
D. Diagram D
The length of time a G protein will signal is determined by the: A. Activity of phsophatases that turn off G-proteins by dephosphorylating Gα B. Activity of phosphatases that turn GTP into GDP C. Degradation of the G protein Adler Gα separates from Gβγ D. GTPase activity of Gα
D. GTPase activity of Gα
The length of time a G protein will signal is determined by the A. Activity of phosphatases that turn off G proteins by dephosphorylating Gα. B. Activity of phosphatases that turn GTP into GDP. C. Degradation of the G protein after Gα separates from Gβγ. D. GTPase activity of Gα.
D. GTPase activity of Gα.
All members of the nuclear receptor family A. Are cell-surface receptors. B. Do not undergo conformational changes. C. Are found only in the cytoplasm. D. Interact with signal molecules that diffuse through the plasma membrane.
D. Interact with signal molecules that diffuse through the plasma membrane.
Compared to cells with normal GTP, what would result if a G protein-coupled receptor was activated but treated with a nonhydrolyzable version of GTP (a form of GTP that cannot be converted to GDP) that was taken up by the cells? These treated cells would have: A. decreased cAMP and decreased protein kinase A (PKA) activity. B. decreased cAMP and increased protein kinase A (PKA) activity. C. increased cAMP and decreased protein kinase A (PKA) activity. D. increased cAMP and increased protein kinase A (PKA) activity.
D. increased cAMP and increased protein kinase A (PKA) activity.
Which type of protein converts phosphatidyl inositol to phosphatidylinositol phosphate (PIP)? A. G protein B. phospholipase C. phosphorylase D. kinase E. phosphatase
D. kinase
Which type of protein adds cleaves a phospholipid into the lipid-derived second messengers, inositol trisphosphate (IP3) and diacylglycerol (DAG)? A. phosphatase B. phosphorylase C. G protein D. phospholipase E. kinase
D. phospholipase
Cyclic AMP (cAMP) is an example of a(n): A. effector or target protein. B. ligand. C. G protein. D. second messenger.
D. second messenger.
Which of these are second messengers generated by phospholipase C? A. inositol trisphosphate and cyclic AMP B. PIP2 and PIP C. cyclic AMP and Ca++ ions D. diacylglycerol and protein kinase C E. diacylglycerol and inositol trisphosphate
E. diacylglycerol and inositol trisphosphate
Which type of protein adds a phosphate group to another molecule? A. phosphatase B. phosphorylase C. G protein D. phospholipase E. kinase
E. kinase