https://quizlet.com/_6q0qbm Chapter 11 1. Which of the following statements about quorum sensing is FALSE? Quorum sensing… ANSWER: is a cell-cell communication in eukaryotes 2. In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function? ANSWER: aggregation of bacteria that can cause cavities 3. Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells. ANSWER: Paracrine signaling 4. Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must… ANSWER: have receptors that recognize and bind the hormone molecule 5. In which of the following ways do plant hormones differ from hormones in animals. ANSWER: Plant hormones often travel in air as gas 6. When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway? ANSWER: Signal molecule 7. Put the steps of the process of signal transduction in the order they occur. ANSWER: A signal molecule binds to a receptor. A conformational change in the signal-receptor complex activates an enzyme. Second messenger molecules are released. Protein kinases are activated. Target proteins are phosphorylated. 8. Testosterone functions inside a cell by… ANSWER: binding with a receptor protein that enters the nucleus and activates specific genes 9. One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this? ANSWER: Receptor tyrosine kinases 10. Which of the following types of signaling is represented in the figure. ANSWER: Synaptic 11. Which observation suggested to Sutherland the involvement of a second messenger in epinephrine’s effect on liver cells? ANSWER: Glycogen breakdown was observed only when epinephrine was administered to intact cells 12. A G-protein receptor with GTP bound to it ANSWER: is in its active site 13. Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because____ ANSWER: Intracellular receptors are present only in target cells. 14. Which of the following is the best explanation by the inability of a specific animal cell to reduce the Ca^2+ concentration in its cytosol compared with the extracellular fluid? ANSWER: insufficient ATP levels in the cytosol 15. In general, a signal transmitted via phosphorylation of a series of proteins…. ANSWER: results in a conformational change to each protein 16. Which of the following would be inhibited by a drug that specifically block the addition of phosphate groups to proteins? NSWER: receptor tyrosine kinase activity A 17. Binding of a signal molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane. ANSWER: Ligand-gated ion channel 18. If an animal cell suddenly lost the ability to produce GTP, what might happen to it's signaling system. ANSWER: It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane. 19. The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is not a problem for steroids because___. ANSWER: Steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane 20. Which of the following is a correct association? ANSWER: GTPase activity and hydrolysis of GTP to GDP 21. If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound ________. ANSWER: to block G protein activity in liver cells 22. Consider this pathway: epinephrine > G protein-coupled receptor > G Protein > adenylyl cyclase > cAMP. The second messenger in this pathway is _____. ANSWER: cAMP 23. 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? ANSWER: Estrogen binds to specific receptors inside many kinds of cells, each with different responses 24. Transcription Factors____. ANSWER: Control Gene expression 25. Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they _________. ANSWER: amplify the original signal many times 26. Which of the following describes the events of apoptosis? ANSWER: 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. 27. Why is apoptosis potentially threatening to the healthy “neighbors” of a dying cell? ANSWER: lysosomal enzymes exiting the dying cell would damage surrounding cells 28. In a phosphorylation cascade (transduction pathway), a series of different molecules in a cell signaling pathway are phosphorylated. Each molecule adds a phosphate group to the next one in line. Protein phosphatases are enzymes that dephosphorylate each molecule returning the previous one to its inactive form. Use information from the figure to select which sentence best describes what would occur if the protein phosphatases were inhibited. ANSWER: signals would continue to be sent as there is no mechanism to turn off the signal Chapter 12 1. What is the final result of mitosis in a human? ANSWER: genetically identical 2n somatic cells 2. If there are 20 duplicated chromosomes in a cell, how many centromeres are there? ANSWER: 20 3. The first gap in the cell cycle (G1) corresponds to… ANSWER: normal growth and cell function 4. In human and many other eukaryotic species’ cells, the nuclear membrane has to disappear to permit____. ANSWER: cytokinesis 5. The mitotic spindle is a microtubular structure that is involved in… ANSWER: separation of sister chromatids 6. Which of the following are primarily responsible for cytokinesis in plant cells but not in animal cells? ANSWER: centrioles and centromeres 7. Kinetochore microtubules assist in the process of splitting centromeres by… ANSWER: creating tension by pulling toward opposite poles 8. During which phase of mitosis do the chromatids become chromosomes. ANSWER: anaphase 9. FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in bacterial cytokinesis. Its function is analogous to… ANSWER: the cleavage furrow of eukaryotic animal cells 10. How is plant cell cytokinesis different from animal cell cytokinesis. ANSWER: Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow. 11. Some cells have several nuclei per cell. How could such multinucleated cells be explained? ANSWER: the cell underwent repeated mitosis, but cytokinesis did not occur 12. Taxol, is an anticancer drug extracted from the pacific yew tree. In animal cells, taxol disrupts microtubule formation. Surprisingly, this stops mitosis. specifically , taxol must affect____. ANSWER: the structure of the mitotic spindle 13. Movement of the chromosomes during anaphase would be most affected by a drug that prevents… ANSWER: shortening of microtubules 14. Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA? ANSWER: G2 15. The beginning of anaphase is indicated by which of the following? ANSWER: Cohesion is cleaved enzymatically 16. The drug cytochalasin B blocks the function of actin. Which of the following aspects of the cell cycle would be most disrupted by cytochalasin B? ANSWER: Cleavage furrow formation and cytokinesis 17. Neurons and some other specialized cells divide infrequently because they… ANSWER: have entered into G0 18. Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis? ANSWER: The cyclin component of MPF is degraded 19. The M-phase checkpoint ensures that all chromosomes are attached to the mitotic spindle. If this does not happen, cells would most likely be arrested in… ANSWER: metaphase 20. Motor proteins require which of the following to function in the movement of chromosomes toward the poles of the mitotic spindle? ANSWER: ATP as an energy source 21. What is the correct chromosomal condition at prometaphase of mitosis? ANSWER: B (4 chromosomes scattered) 22. What is the correct chromosomal condition for one daughter nucleus at telophase of mitosis? ANSWER: E 23. If the cell whose nuclear material is shown in the accompanying figure continues toward completion of mitosis, which of the following events would occur next? ANSWER: formation of telophase nuclei 24. MPF is a dimer consisting of____. ANSWER: Cyclin and a cyclin-dependent kinase 25. Which of the following triggers the cell’s passage past the G2 checkpoint into mitosis? ANSWER: MPF 26. In the figure, G1 is represented by which numbered parts of the cycle? ANSWER: I or V 27. In the figure above, which number represents DNA synthesis? ANSWER: 2 28. Density-dependent inhibition is explained by which of the following? ANSWER: as cells become more numerous, the cell surface proteins of one cell contact the adjoining cells and they stop dividing 29. Besides the ability of some cancer cells to overproliferate, what else could logically result in a tumor? ANSWER: lack of appropriate cell death 30. A research team began a study of a cultured cell line. Their preliminary observation showed them that the cell line did not exhibit either density-dependent inhibition or anchorage dependence. What could they conclude right away? ANSWER: the cells show characteristics of tumors 31. For a chemotherapeutic drug to be useful for treating cancer cells, which of the following is most desirable? ANSWER: it interferes with rapidly dividing cells 32. Cells from advanced malignant tumors often have very abnormal chromosomes and an abnormal number of chromosomes. What might explain the association between malignant tumors and chromosomal abnormalities? ANSWER: cell cycle checkpoints are not in pace to stop cells with chromosome abnormalities
