Cell Bio Exam 4
During the G2 checkpoint the cell is assessed with regard to
DNA replication
Which of the following will decrease the level of cAMP?
Decrease the activity of adenylate cyclase Submit
When an abnormal, indestructible form of mitotic cyclin is introduced into cells, they enter into mitosis but cannot emerge from it and reenter G1 phase.
Destruction of mitotic cyclin - and hence the inactivation of mitotic Cdk - are required before cells can complete mitosis and begin a new cell cycle.
Which of these is NOT an example of the protein product of an oncogene?
a tumor suppressor
Autophosphorylation is an important part of the mechanism of the receptor tyrosine kinases. Why is this?
The phosphorylation provides sites for recruitment of other signal transduction molecules.
Which of the following would be a reasonable therapeutic strategy to inhibit cancer metastasis?
inhibition of VEGF/FGF secretion
What is another likely role of the SNARE mechanism of vesicle fusion, in addition to secretion of material?
insertion of membrane proteins into the plasma membrane
You are an epidemiologist/pathologist working in a lab analyzing tissue samples. An oncologist brings two biopsies of two different tumors from the same patient. She would like to know which tumor is more malignant and requires more aggressive and timely treatment. Which of the following morphological features of the biopsies will dictate which tumor is more malignant?
The tumor with a high nucleus-to-cytoplasm ratio should require more aggressive and timely treatment.
The dominant negative mutation of the receptor in the animation is effective in blocking the hormone signal because
it is able to dimerize with a functional receptor without the activation of autophosphorylation.
Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of the process. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response. Drag each item to the appropriate bin.
-reception: .G protein-coupled receptor .receptor tyrosine kinase .signaling molecule -transduction: .phosphorylation cascade .second messenger .adenylyl cyclase .Ca2+ .cAMP .IP3 -response: .protein synthesis
Unlike steroid hormones, signaling molecules that are large and/or hydrophilic cannot pass through the cell's plasma membrane and therefore must bind extracellularly to receptor molecules in the plasma membrane. Two types of signal receptors embedded in the cell's plasma membrane are G protein-coupled receptors and receptor tyrosine kinases. Classify each phrase by whether it applies to G protein-coupled receptors only, receptor tyrosine kinases only, both receptors, or neither receptor. Drag each phrase to the appropriate bin.
-G protein-coupled receptors: .interact directly with G proteins -receptor tyrosine kinases: .Catalyzes transfer of a phosphate group to receptor .binding of the signaling molecule forms a dimer -Both types of receptors: .receptor is located in the plasma membrane .binding site for signaling molecule is located on the extracellular side of the cell -neither: .binding of the signaling molecule allows ions to flow through a channel in the receptor
Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor on target cells is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine. Which statements are true about the binding of histamine to the histamine H1 receptor? Select all that apply.
-Histamine binds extracellularly to the H1 receptor. -When histamine binds to the H1 receptor, the receptor undergoes a conformation change and binds the inactive G protein. -Once the G protein is active, it binds to the enzyme phospholipase C, activating it. -Histamine is likely hydrophilic.
The mitotic index is a measure of the mitotic activity of a population of cells. It is calculated as the percentage of cells in mitosis at any one time. Assume that upon examining a sample of 1000 cells, you find 30 cells in prophase, 20 in prometaphase, 20 in metaphase, 10 in anaphase, 20 in telophase, and 900 in interphase. Of those in interphase, 400 are found (by staining the cells with a DNA-specific stain) to have XX amount of DNA, 200 to have 2X2X, and 300 cells to be somewhere in between. Autoradiographic analysis indicates that the G2G2 phase lasted 4 hours.
-Mitotic index: 10% -Specify the proportion of the cell cycle spent in each of the following phases: prophase, prometaphase, metaphase, anaphase, telophase, G1, S, and G2: 3% of time in prophase, 2% in prometaphase, 2% in metaphase, 1% in anaphase, 2% in telophase, 40% in G1, 30% in S, and 20% in G2. -What is the total length of the cell cycle? 20 hours -What is the actual amount of time (in hours) spent in each of the phases of part B?: 0.6 h in prophase; 0.4 h each in prometaphase, metaphase, and telophase; 0.2 h in anaphase; 8 h in G1; 6 h in S; and 4 h in G2. To measure the G2 phase, radioactive thymidine (a DNA precursor) is added to the culture at some time tt, and samples of the culture are analyzed autoradiographically for labeled nuclei at regular intervals thereafter. What specific observation would have to be made to assess the length of the G2 phase?: The first appearance of label in prophase nuclei would have to be observed. -What proportion of the interphase cells would you expect to exhibit labeled nuclei in autoradiographs prepared shortly after exposure to the labeled thymidine? (Assume a labeling period just long enough to allow the thymidine to get into the cells and begin to be incorporated into DNA.): About 30%, because all cells in S phase will incorporate label immediately, and on the average about 30% of the cells in the culture should be in S phase at any one time.
As in most areas of biology, the study of mitosis and the cell cycle involves a lot of new terminology. Knowing what the different terms mean is essential to understanding and describing the processes occurring in the cell. Drag the terms on the left to correctly complete these sentences. Not all the terms will be used.
1. DNA replication produces two identical DNA molecules, called SISTER CHROMATID(s), which separate during mitosis. 2. After chromosomes condense, the CENTROMERE(s) is the region where the identical DNA molecules are most tightly attached to each other. 3. During mitosis, microtubules attach to chromosomes at the KINETOCHORE(s). 4. In dividing cells, most of the cell's growth occurs during INTERPHASE. 5. The MITOTIC SPINDLE(s) is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division. 6. During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called CHROMATIN. 7. In most eukaryotes, division of the nucleus is followed by CYTOKINESIS, when the rest of the cell divides. 8. The CENTROSOME(s) are the organizing centers for microtubules involved in separating chromosomes during mitosis.
The mitotic spindle consists of two types of microtubules: kinetochore microtubules and nonkinetochore microtubules. In animal cells, these two types of microtubules function differently in the stages of mitosis. Complete the sentences by dragging the terms to the appropriate locations. Terms may be used once, more than once, or not at all.
1. During prophase, the microtubules of the mitotic spindle LENGTHEN. 2. During anaphase, the nonkinetochore microtubules LENGTHEN and move past each other, and the kinetochore microtubules SHORTEN. 3. During telophase, the nonkinetochore microtubules DISASSEMBLE.
Consider an animal cell in which motor proteins in the kinetochores normally pull the chromosomes along the kinetochore microtubules during mitosis. Suppose, however, that during metaphase, this cell was treated with an inhibitor that blocks the function of the motor proteins in the kinetochore, but allows the kinetochore to remain attached to the spindle. The inhibitor has no effect on any other mitotic process, including the function of the nonkinetochore microtubules.
1. Will this cell elongate during mitosis? yes 2. Will the sister chromatids separate from each other? yes 3. Will the chromosomes move to the poles of the cell? no
Cortisol is a steroid hormone that can pass through the plasma membrane. Complete the flowchart describing the interaction of cortisol with intracellular receptors.
1. cortisol passes through the plasma membrane into the cytoplasm. 2. Cortisol-receptor complex forms in the cytoplasm. 3. cortisol-receptor complex enters the nucleus where it binds to genes. 4. cortisol-receptor complex acts as a transcription factor. 5. the transcribed mRNA is translated into a specific protein.
Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine. Complete the flowchart showing the process of histamine signal transduction from the H1 receptor. Drag the labels to their appropriate locations in the flowchart. Some labels will not be used.
1. enzyme cleaves PIP2, forming DAG and IP3 2.IP3 binds to a ligand-gated ion channel in the ER membrane 3. Calcium ions flow through the ligand-gated ion channel 4. Calcium ion concentration increases in the cytosol 5. calcium ions activate a protein, leading to a cellular response
In a population of 1000 cells, 200 are in various phase of the M stage. For those in interphase, 400 have 1X amount of DNA, 200 have 2X amount of DNA, and the rest have somewhere in between 1X and 2X amount of DNA. What is the mitotic index?
20%
In a population of 1000 cells, 200 are in various phase of the M stage. For those in interphase, 400 have 1X amount of DNA, 200 have 2X amount of DNA, and the rest have somewhere in between 1X and 2X amount of DNA. What is the total length of the cell cycle if the S phase has a duration of 5 hours?
25 hours
Botulinum toxin blocks neuromuscular transmission, causing paralysis. How does it do this?
Botulinum toxin cleaves the t-SNARE, blocking fusion of the vesicle.
The cell cycle represents the coordinated sequence of events in the life of a cell from its formation to its division into two daughter cells. Most of the key events of the cell cycle are restricted to a specific time within the cycle. In this exercise, you will identify when various events occur during the cell cycle. Recall that interphase consists of the G1, S, and G2 subphases, and that the M phase consists of mitosis and cytokinesis. Drag each label to the appropriate target.
A. Non-dividing cells exit cell cycle. B. at this point, cell commits to go through the cycle C. DNA replicates D. Cell prepares for mitosis E. Mitotic spindle begins to form F. Cell divides, forming two daughter cells
The chemical substance 2-acetylaminofluorene (AAFAAF) causes bladder cancer when injected into rats but not guinea pigs. If normal bladder cells obtained from rats and guinea pigs are grown in culture and exposed to AAFAAF, neither are converted into cancer cells. How can you explain these findings?
AAFAAF is a "precarcinogen" that needs to be metabolically activated before it can cause cancer. Rats, but not guinea pigs, contain a liver enzyme that catalyzes the metabolic activation of AAFAAF.
What would be a possible result if cells under-expressed Mad or Bub proteins?
APC would be inappropriately activated and chromatids not attached to the spindle could separate, resulting in non-disjunction.
What is the relationship between ATP and cAMP?
ATP is converted into cAMP by adenylate cyclase.
What similarities are there at the molecular level between how cells regulate the rate of GTP hydrolysis by the catalytically active portion of a heterotrimeric G protein and by Ras?
Activation of heterotrimeric G proteins involves a conformational change in a protein with which it associates. Ras activation is stimulated by a conformational change in a guanine nucleotide exchange factor (GEF), such as SOS. Regulator of G protein sigNaling (RGS) proteins increases the rate of hydrolysis of GTP by heterotrimeric G proteins, leading to their inactivation. These are similar to GTPase activating proteins (GAPs), which increase the rate of Ras inactivation.
Each of the following is a cancer a cancer screening procedure except PSA test. mammography. Pap smear. colonoscopy. All are screening procedures.
All are screening procedures. Submit
Does your explanation suggest how to predict whether AAFAAF is carcinogenic in humans without actually exposing humans to AAFAAF?
Analyzing human liver cells to see if they contain the activating enzyme would indicate whether AAFAAF is likely to be carcinogenic in humans.
Why was the word "usually" included in the first sentence?
Because inherited mutations in the gene coding for DNADNA polymerase ηη Because inherited mutations in the gene coding for D N A polymerase η cause a variant form of xeroderma pigmentosum in which excision repair remains intact. D N A polymerase η is a special form of D N A polymerase that catalyzes the translesion synthesis of a new, error-free stretch of D N A across regions in which the template strand is damaged. So inherited defects in D N A polymerase η, like inherited defects in excision repair, hinder the ability to repair pyrimidine dimers. cause a variant form of xeroderma pigmentosum in which excision repair remains intact Because inherited mutations in the gene coding for D N A polymerase η cause a variant form of xeroderma pigmentosum in which excision repair remains intact. D N A polymerase η is a special form of D N A polymerase that catalyzes the translesion synthesis of a new, error-free stretch of D N A across regions in which the template strand is damaged. So inherited defects in D N A polymerase η, like inherited defects in excision repair, hinder the ability to repair pyrimidine dimers. . DNADNA polymerase ηη Because inherited mutations in the gene coding for D N A polymerase η cause a variant form of xeroderma pigmentosum in which excision repair remains intact. D N A polymerase η is a special form of D N A polymerase that catalyzes the translesion synthesis of a new, error-free stretch of D N A across regions in which the template strand is damaged. So inherited defects in D N A polymerase η, like inherited defects in excision repair, hinder the ability to repair pyrimidine dimers. is a special form of DNADNA polymerase that catalyzes Because inherited mutations in the gene coding for D N A polymerase η cause a variant form of xeroderma pigmentosum in which excision repair remains intact. D N A polymerase η is a special form of D N A polymerase that catalyzes the translesion synthesis of a new, error-free stretch of D N A across regions in which the template strand is damaged. So inherited defects in D N A polymerase η, like inherited defects in excision repair, hinder the ability to repair pyrimidine dimers. the translesion synthesis of a new, error-free stretch Because inherited mutations in the gene coding for D N A polymerase η cause a variant form of xeroderma pigmentosum in which excision repair remains intact. D N A polymerase η is a special form of D N A polymerase that catalyzes the translesion synthesis of a new, error-free stretch of D N A across regions in which the template strand is damaged. So inherited defects in D N A polymerase η, like inherited defects in excision repair, hinder the ability to repair pyrimidine dimers. of DNADNA across regions in which the template strand is damaged. So inherited defects in DNADNA polymerase ηη Because inherited mutations in the gene coding for D N A POLYMERASE η cause a variant form of xeroderma pigmentosum in which excision repair REMAINS INTACT. D N A POLYMERASE η is a special form of D N A polymerase that CATALYZES the translesion ~synthesis of a new, error-free stretch ~of DNA across regions in which the template strand is damaged. So inherited defects in DNA POLYMERASE η, like inherited defects in excision repair, hinder the ability to repair pyrimidine dimers. , like inherited defects in excision repair, hinder the ability to repair pyrimidine dimers.
Describe two pieces of evidence supporting the idea that angiogenesis is required for tumors to grow beyond a tiny clump of cells. Drag the terms on the left to the appropriate blanks on the right to complete the sentences.
Cancer cells injected into an isolated rabbit thyroid gland kept alive with a nutrient solution FAIL TO LINK UP to the organ's blood vessels, the tumors grow to 1-2 MM IN DIAMETER. When injected into live animals, the same tumors BECOME INFILTRATED WITH blood vessels and grow to ENORMOUS SIZE. Cancer cells placed in the anterior chamber of a rabbit's eye, where there are no blood vessels, REMAIN ALIVE and reach 1-2 MM IN DIAMETER. In contrast, cancer cells placed directly on the iris BECOME INFILTRATED WITH blood vessels and the tumors grow to ENORMOUS SIZE.
Describe the first stage involved in metastasis.
Cancer cells invade surrounding tissues and penetrate through the walls of lymphatic and blood vessels, thereby gaining access to the bloodstream. The first step is facilitated by decreased cell-cell adhesion, increased motility, and secretion of proteases that degrade the extracellular matrix and basal lamina. Submit
Describe the third stage involved in metastasis.
Cancer cells leave the bloodstream and enter particular organs, where they establish new metastatic tumors. During the third step, the sites to which cancer cells tend to metastasize are determined by the location of the first capillary bed encountered as well as organ-specific conditions that influence cancer cell growth.
Describe two pieces of evidence supporting the idea that cancer cells secrete molecules that stimulate angiogenesis.
Cancer cells produce and secrete angiogenesis-activating proteins called vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF), which bind to receptor proteins on the surface of endothelial cells. The activated endothelial cells then organize into hollow tubes that develop into new blood vessels. When cancer cells are placed in a chamber surrounded by a filter possessing tiny pores that cells cannot pass through, and the chamber is then implanted into animals, new capillaries proliferate in the surrounding host tissue. Since the cancer cells cannot pass through the filter, the most straightforward interpretation is that the cells produce molecules that diffuse through the tiny pores in the filter and activate angiogenesis in the surrounding normal tissue. Submit
Treatment of cells with organic compounds that enter the cell and bind with high affinity to the active site of caspase-3.
Caspase-3 is a key activator of the apoptosis pathway, so inhibiting it would suppress cell death.
Different chemotherapeutic drugs can do each of the following except inhibit DNA topoisomerases required for DNA replication. inhibit metabolic pathways required for DNA synthesis. disrupt spindle microtubules.chemically cross-link DNA strands.
Chemotherapeutic drugs can do all of the above.
G1 and M
Chromosomes are in an extended form during G1, but in a condensed form during most of M phase. Submit
G2 and M
Chromosomes are in an extended form during G2, but in a condensed form during most of M phase. Submit
Which of these is NOT correct? Cyclic AMP binds to calmodulin. Ion channels are found on both the plasma membrane and the endoplasmic reticulum. Kinases are enzymes that phosphorylate other molecules. Tyrosine-kinase receptors consist of two polypeptides that join when activated by a signal molecule. Phospholipase C catalyzes the formation of IP3.
Cyclic AMP binds to calmodulin.
The following second messenger activates protein kinase C
DAG
G1 and S
DNA is being synthesized during S; little or no synthesis occurs during G1.
Describe the second stage involved in metastasis.
During the second step, the cancer cells are transported by the circulatory system throughout the body. Only a tiny fraction of the cancer cells that enter the bloodstream survive the trip and establish successful metastases.
A student wishes to develop a novel strategy to inhibit cancer metastasis involving the use of gene therapy to introduce a virus with a constitutively expressing gene into tumor cells to enhance cell-cell adhesion. Which of the following molecules should the student focus on to constitutively express through gene therapy?
E-cadherin
Match the infectious agent with the appropriate cancer type. Drag the appropriate labels to their respective targets.
Epstein-Barr viruts: burkitt's lymphoma hepatitis b virus: liver cancer human papilloma virus: cervical cancer H. pylori: stomach cancer Parasitic flatworms: bladder cancer
A researcher generates a mutant cell line in a laboratory culture in which the mutants have an RGS-GAP that is increased in activity. What is the likely outcome of this mutation?
G protein-mediated cellular signaling will terminate faster. Submit
A toxin that inhibits the production of GTP would interfere with the function of a signal transduction pathway that is initiated by the binding of a signal molecule to _____ receptors.
G-protein-linked
Epinephrine acts as a signal molecule that attaches to _____ proteins.
G-protein-linked receptor Submit
G1 and G2
G1 has the 2C amount of DNA; G2 has the 4C amount.
Which of the following is NOT a category for the gene product for an oncogene? -Transcription factor -Glycolysis enzyme -nonreceptor protein kinase -growth factor receptor -growth factor
Glycolysis enzyme
Which of these second messengers opens calcium channels?
IP3
Cells are treated with a small molecule called pifithrin-alpha, which was originally isolated for its ability to reversibly block p53-dependent transcriptional activation. Select the three correct statements.
In such cells, apoptosis would be less likely to occur, and they would be more likely to divide. Puma would not be expressed, leading to more efficient inhibition of mitosis. p21 would not be expressed, leading to loss of cell cycle arrest. Submit
When mitotic Cdk-cyclin is injected into cells that have just emerged from S phase, chromosome condensation and nuclear envelope breakdown occur immediately, rather than after the normal G2 delay of several hours. Select the four correct statements.
It is possible to trigger chromosome condensation and nuclear envelope breakdown prematurely by experimentally introducing mitotic Cdk-cyclin into cells that have just emerged from S phase. Phosphorylation of condensins and lamins contributes to chromosome condensation and nuclear envelope breakdown. Mitotic Cdk-cyclin is normally activated at the end of G2. Mitotic Cdk-cyclin catalyzes the phosphorylation of condensins and lamins. Submit
Based on the graph, how long does it take for maximal Ras activation to be achieved?
It takes approximately 1.5−−2 min to reach maximal Ras activation
Which of the following outcomes would you expect to see if Ras were to acquire a mutation in which its GTPase activity were abolished?
MAP kinases will be continuously activated, promoting continual and repeating mitotic divisions.
Cancer cell aneuploidy (the gain or loss of chromosomes) is most likely caused by a defect in
Mad.
Imagine that you are a graduate student working in a cancer lab. You accidentally mix unlabeled tubes of carcinoma cells with tubes of normal epithelial cells. Which of the following is NOT a possible strategy to allow you to distinguish which tubes contain carcinoma cells?
Monitor the rate of cell division.
How could you determine which sample contains the cancer cells?
Normal cells: dont divide more than 50-60 times in culture. need anchorage for growth. cancer cells: produce tumors being injected into nude mice. grow to higher population densities in culture. have mechanisms for replenishing their telomeres in culture. grow well in culture.
Phosphorylated p53 can act as a transcription factor. When there is major damage to the genome, p53 increases the transcrption of which gene?
PUMA
Why does Ras activity decline after a few minutes, even when EGF is still present?
Ras activity gradually decreases due to the action of RasGAPs, which stimulate Ras to hydrolyze GTP to GDP, inactivating Ras.
What kind of receptor is likely to be involved in responding to bacterial proteins?
Pertussis toxin ADP ribosylates certain G proteins. It would be likely that a neutrophil responds to bacterial proteins through a G protein-linked receptor.
Mitosis unfolds through a sequence of stages marked by specific events in the cell. The structural changes in the cell are brought about by a series of tightly coordinated underlying mechanisms. Sort each process into the appropriate bin to indicate the stage of mitosis in which it occurs. If a process occurs in more than one stage, sort it to the stage when it first occurs.
Prophase: -cohesins join sister chromatids of duplicated chromosome -tubulins assemble into spindle microtubules Prometaphase: -microtubules attach to kinetochores Metaphase: -kinetochores are motionless in relation to poles of cell Anaphase: -Cohesins break down -kinetochores move toward poles of cell Telophase: -spindle microtubules disassemble
Why do you suppose that the concentration of p53 is controlled by its degradation rather than at the level of its transcription like many other proteins?
Protection from degradation allows for a much faster build up in response to changes in cellular conditions.
Mutations that inactivate the main protein phosphatase used to catalyze protein dephosphorylations cause a long delay in the reconstruction of the nuclear envelope that normally takes place at the end of mitosis.
Proteins phosphorylated by mitotic Cdk-cyclin at the beginning of prophase must be dephosphorylated again before cells can finish mitosis
Children with xeroderma pigmentosum usually cannot carry out excision repair. Why does this makes them so susceptible to developing cancer?
Pyrimidine dimers caused by exposure to sunlight can create mutations that lead to cancer, and one of the main mechanisms for repairing such defects is excision repair.
What is the role of Rab GTPase in the process?
Rab GTPase locks the t-SNARE and v-SNARE together, facilitating fusion of the vesicle.
A person who smokes for the first time tends to experience much more severe effects from a cigarette than does someone who smokes frequently. Given that the smoke contains nicotine, provide a reasonable explanation for this difference. Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.
Smokers DO develop tolerance to nicotine. Therefore, it would be reasonable to suggest that CHRONIC exposure to nicotine might lead to RECEPTOR DOWN-REGULATION as a basis for this tolerance.
Exposing cells to recombinant TRAIL protein, a ligand for the tumor necrosis factor family of receptors.
TRAIL would activate pathways similar to TNF-alpha, a known stimulator of apoptosis.
The annual incidence of colon cancer in the United States is about 55 cases per 100,000. Because colon cancer often causes bleeding, doctors sometimes use a screening procedure called the fecal occult blood test (FOBT) to look for tiny amounts of blood in the feces. One form of this test has a specificity of about 98%, which means that when it indicates the presence of blood in the feces, the result is an error (i.e., cancer is not present) only 2% of the time. While this may seem like excellent specificity, a 2% "false positive" rate makes this test almost useless as a tool for colon cancer screening. Why is this test almost useless as a tool for colon cancer screening?
Testing 100,000 people, the 2% false positive rate yields many more incorrect results (2,000) compared to real cancer cases (55).
Upon binding to the receptor, the Gβγ subunit catalyzes GDP/GTpexchange by the Gα subunit. How is this similar to the activation of Ras by a receptor tyrosine kinase? Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used.
The activation of RAS requires the assistance of another protein called SOS Upon binding to the TYROSINE kinase receptor, SOS catalyzes the RAsGDP/GTP exchange reaction. In this respect, SOS and RAS together are similar to a heterotrimeric G protein. Here, SOS acts like the G BETA GAMMA subunits, whereas RAS is similar to a G ALPHA subunit. .
Which of the following would be expected if a researcher added an inhibitor of cyclin-dependent kinases (Cdk) at the end of prophase and beginning of prometaphase?
The nuclear envelope would not break down.
Why do you think beta-blockers are effective in reducing blood pressure? Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Terms can be used once, more than once, or not at all.
The binding of EPINEPHRINE to beta-adrenergic receptors causes A STIMULATION of heart function, both in terms of heart rate and with respect to the amount of work done in pumping blood. The effect appears to be mediated by CYCLIC AMP. When an antagonist such as the beta blocker propranolol is given to patients with hypertension, the cellular response caused by the binding of EPINEPHRINE to beta receptors is PARTIALLY INHIBITED. Heart function is gradually restored over a period of time, with a corresponding DECREASE in blood pressure.
A mutant cell line is produced in which a motor protein specific for astral microtubules is inactivated. Which of these statements accurately describes the status of the cells and functional consequence of the mutation?
The cells will be stuck in anaphase because the astral motor proteins cannot help pull the spindle to the spindle poles.
Using these tools, describe how you could demonstrate that a hormone exerts its effect by (1) causing Ca2+ to enter the cell through channels or (2) releasing Ca2+ from intracellular stores such as the ER.
The chelator could be added to the extracellular medium to REDUCE the calcium levels OUTSIDE the cell. Addition of the chelator to the extracellular medium should BLOCKthe action of the hormone if it depends on calcium influx. If the action of the hormone depends solely on calcium release from INTRACELLULAR stores, then addition of a calcium ionophore should MIMIC the action of the hormone. In this case, the ionophore should be EFFECTIVE even when EGTA is added to the extracellular medium to reduce the free calcium ion concentration.
What would be the effect of adding colchicine to cells that were at the metaphase-anaphase transition?
The chromosomes would segregate but the cell would not elongate. Submit
What activity do APC and Mdm2 share?
They are ubiquitin ligases.
Which of the following is NOT true of both ATP and cAMP?
They both have the same number of ring structures.
Many chemicals are more mutagenic after being processed in the liver.
True
The anti-angiogenic drug Avastin works by binding to and inhibiting the activity of
VEGF
Consider the mechanism of Botulinum toxin. Is this toxin reversible?
Yes, however the cell must regenerate new t-SNAREs.
Receptor tyrosine kinases are activated by hormones that cause cell division (mitogens). Which of the following describes a way that a protein in the pathway could be mutated to result in its constitutive activation causing unregulated cell division?
a mutation in Ras that makes it unable to hydrolyze GTP
Which of the following would be a histological indicator of a pre-cancerous or cancerous state in intestinal epithelial cells?
accumulation of beta-catenin in the nucleus of the colon epithelium Submit
Which of the following experimental strategies could be used to block the IP3 branch but not the DAG branch of the IP3 pathway?
adding an antagonist of the IP3 receptor
cAMP is an abbreviation for
adenosine 3',5'-cyclic monophosphate
Which microtubules shrink during mitosis?
astral and kinetochore microtubules
The molecular motors that are most active in Prophase are the ones attached to __________.
astral microtubules
The difference between benign and malignant tumors is
benign tumors have not spread to other sites.
Which of these is the second messenger that leads to glucose mobilization?
cAMP
Which of the following reactions is catalyzed by a phosphodiesterase?
cAMP converted to AMP
Match the second messenger with the properties. Drag the terms on the left to the appropriate blanks on the right.
cAMP: glucose mobilization IP3: opens calcium ion channels DAG: activates protein kinase C calcium: binds to calmodulin cGMP: smooth muscle relaxation
Which of these second messengers triggers vasodilation (think Cialis)
cGMP
Which of these is the second messenger for calmodulin?
calcium
Which of these is activated by calcium ions?
calmodulin
Hormones that use the tyrosine kinase receptor mechanism as shown in the animation are important for
cellular growth and survival.
Which protein holds the sister chromatids together?
cohesions
Each of the following can contribute to proliferation of cancer cells except
density-dependent inhibition of growth.
Organ transplant patients often develop cancers at rates higher than normal. This observation supports the idea that cancer formation is dependent on
evasion of immune surveillance.
The cleavage of glycogen by glycogen phosphorylase releases _____.
glucose-1-phosphate
Which of the following is NOT a mechanism used to temporally regulate the activity of maturation-promoting factor (MPF)?
glycosylation
Sos activates Ras. Sos is an example of a
guanine-nucleotide exchange factor (GEF).
Based on the direction of movement, the kinetochore molecular motor is most likely _____-based.
kinesin
What protein complex or complexes provide initial recognition of the vesicle with the target membrane?
multisubunit tethering proteins and coiled-coil tethering proteins
Polycyclic aromatic hydrocarbons in tobacco smoke are potent carcinogens because they preferentially bind to, and trigger base substitutions, in the
p53 gene.
A physician using a microscope to examine suspect cells in biopsy tissue would expect to find each of the following characteristics in metastatic cancer cells except
perfectly spherical nuclei.
Which type of microtubule is responsible for the elongation of the cell in Anaphase B?
polar
In order to be active, a Cdc-cyclin needs to be
singly phosphorylated
In the Ames Test, the appearance of his+ revertants in the presence of a non-mutagenic control compound indicates that _______.
some of the reversion mutations are not caused by the mutagen being tested
The purpose of the Ames Test is to _______.
test the mutagenic effects of chemicals
A new compound developed in the lab was tested as a DNA mutagen. When the Ames test was 2) performed, the results were numerous bacterial colonies following exposure. This result means
the chemical is a mutagen and may also be a carcinogen
Alpha- and beta-adrenergic receptors can bind epinephrine and norepinephrine, yet they trigger different signal transduction pathways. This is because __________.
the receptors activate different G proteins
The histamine H1 receptor is one of several existing histamine G protein-coupled receptors. Depending on many factors, including the type of receptor, histamine can trigger a variety of responses, including vasodilation, smooth muscle contraction, stimulation of gastric secretion, cardiac stimulation, and increased vascular permeability (causing runny nose and watery eyes). Which of the following could account for the different cellular responses to histamine? Select all that apply.
the types of relay molecules within the cell the enzyme that is activated by the G protein associated with the receptor the cell type in which the histamine receptor is located the type of second messengers involved in the signal transduction pathway