Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances? Show
A. The proteins receive electrical signals from nerve cells. C. The proteins interact directly with proteins on the surfaces of other cells. When the concentration of GAl is highest, the average height of the control seedlings is approximately A. 10 cm a. 10 Which of the following is a correct conclusion that can be drawn from the data in Figures 1, 2, and 3? A. Most of the increase in the concentration of all gibberellins 40 to 45 days after planting is due to an increase in the concentration of GAl. Which of the following statements best describes how a growth factor stimulates cell division from outside a cell? A. The growth factor binds to other cells in the same area and holds them together to form a large, multicellular structure. B. The growth factor binds to receptors on the cell surface, initiating a signal transduction pathway that activates specific target genes. Type 1 diabetes results from the destruction of insulin-producing cells in the pancreas. Individuals with type 1 diabetes produce insufficient amounts of insulin, a hormone that regulates the
concentration of glucose in the blood. A. The drug will have little or no effect on the signaling pathway because the receptors will not be activated in the absence of insulin. A. The drug will have little or no effect on the signaling pathway because the receptors will not be activated in the absence of insulin. Which of the following statements best predicts the effect of a mutation that results in a loss of the glucocorticoid receptor's ligand binding function? A. The transduction of the glucocorticoid signal across the plasma membrane will be blocked. B. The glucocorticoid receptor will remain associated with the accessory proteins. The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase? A. Residual blood thyroxine, from prior to thyroid gland removal, will bind to cells in the
anterior pituitary, signaling more TSH secretion. D. A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion. The model shown in the figure represents the role of two hormones, calcitonin and parathyroid hormone (PTH), in maintaining normal blood calcium levels in humans. If a dietary change results in an increase in blood calcium concentration above normal levels, which of the following is the most likely effect on calcium homeostasis? A. Calcitonin levels will decline, thus stimulating the release of PTH. B. Calcitonin levels will rise, thus promoting the deposit of calcium into bones. Trypsinogen is split by the enzyme enterokinase to form an activated molecule of the protease trypsin. Which of the following would confirm that the activation of trypsin is an example of how a positive feedback mechanism can amplify a biological process? A. The activated trypsin enzyme can use enterokinase as a substrate. B. The trypsin produced by the reaction is capable of splitting and activating additional trypsinogen molecules. A student claims that the Y chromosome contains the
sex-determining region gene, known as the SRY gene, which causes male fetuses to develop testes. A. The SRY gene produces a protein that binds to specific regions of DNA in certain tissues, which affects the development of these tissues. A. The SRY gene produces a protein that binds to specific regions of DNA in certain tissues, which affects the development of these tissues. An antigen can induce an immune response in a host organism. Antigens are targeted by antibodies that are
produced by the organism's immune system in response to contact with the antigen. Antibodies are specific to antigens. Many different cell types are involved in immune responses. A. Chemicals that are secreted from antigen-presenting cells then activate helper T cells. A. Chemicals that are secreted from antigen-presenting cells then activate helper T cells. Adjacent plant cells have narrow channels called plasmodesmata that pass through the cell walls of the connected cells and allow a cytoplasmic connection between the cells. A. They allow the movement of molecules from one cell to another, enabling communication between cells. A. They allow the movement of molecules from one cell to another, enabling communication between cells. A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of the brain. The hormone targets specific cells in many parts of the body. A. The hormone interacts with the nerves at the base of the brain and directs signals to the target cells through the nervous system. C. The hormone is released into the bloodstream where it can be transported to all cells with the correct receptors. G proteins are a family of receptor proteins that are involved in transmitting signals from outside a cell to inside a cell. When a signaling molecule binds to a G protein, the G protein is activated. The G protein
then activates an enzyme that produces a second messenger called cAMP. A. cAMP carries the signal to the nucleus of the cell and results in new sequences of nucleotides being added to the cell's DNA. D. cAMP results in the activation of an enzyme that amplifies the signal by acting on many substrate molecules. Metformin is a drug used to treat type 2 diabetes by decreasing glucose production in the liver. AMP-activated protein
kinase (AMPK) is a major cellular regulator of glucose metabolism. Metformin activates AMPK in liver cells but cannot cross the plasma membrane. By blocking AMPK with an inhibitor, researchers found that AMPK activation is required for metformin to produce an inhibitory effect on glucose production by liver cells. A. It is a secondary
messenger that amplifies a signal through a cascade reaction. B. It is a ligand that activates the signal transduction pathway of the activation of AMPK. Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell? C. A ligand binds to a receptor. During a fight-or-flight
response, epinephrine is released into the body's circulatory system and transported throughout the body. Some cells exhibit a response to the epinephrine while other cells do not. A. Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors for epinephrine. Only cells with such receptors are capable of
responding. A. Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors for epinephrine. Only cells with such receptors are capable of responding. Signal transduction may result in changes in gene expression and cell function, which may alter phenotype in an embryo. An example is
the expression of the SRY gene, which triggers the male sexual development pathway in mammals. This gene is found on the Y chromosome. A. If the SRY gene is absent or nonfunctional, the embryo will exhibit male sexual development. B. If the SRY gene is absent or nonfunctional, the embryo will exhibit female sexual development. Researchers have discovered details about apoptosis (programmed cell death) by studying embryologic development of a nematode worm, Caenorhabditis elegans. Apoptosis is a normal
developmental process in C. elegans. They found several genes involved in apoptosis, including ced−9 and ced−3 . The ced−3 gene was found to promote cell death, and ced−9 to inhibit it. The ced−9 gene serves as a regulator that prevents apoptosis in the absence of a signal promoting apoptosis. A. An experiment showed that a mutation
in the ced−9 gene led to excessive cell death in C. elegans. A. An experiment showed that a mutation in the ced−9 gene led to excessive cell death in C. elegans. Which of the following statements best predicts the effect of a loss of function of the insulin receptor's intracellular domain? A. The stimulation of the signal transduction pathway will increase. B. The storage of GLUT4 in vesicles inside the cell will increase. Which of the following outcomes will most likely result from the inactivation of the beta-2 adrenergic receptor? A. The cellular concentration of cyclic AMP will increase. D. The rate of glycogen synthesis in the cell will increase. Which of the following changes in the FGFR signaling pathway is most likely to result in uncontrolled cell proliferation? A. The irreversible association of FGFR proteins
A. The irreversible association of FGFR proteins A researcher found a mutation that resulted in the PFK enzyme being unable to bind ATP to the allosteric site. Which of the following best predicts the effect of the mutation? A. The activity of the enzyme will not be affected because the active site is not involved in substrate binding at the allosteric site. B. Negative feedback regulation does not occur, so the enzyme will be active when glycolysis is not needed. Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 p.m.? A. Immediately after the meal, the blood glucose level will decrease because of the increase in glucagon levels. B. Immediately after the meal, the blood glucose level will increase, and then insulin will be secreted to counter the increase. Warfarin is a drug used to treat certain blood clots. Warfarin blocks the formation of the active form of vitamin K-dependent clotting factors. Based on the model, which of the following best predicts the effects of warfarin on a patient? A. Fibrinogen will form fibrin, but the clot will not form because Factor XIII will not be synthesized. D. Factor X will not be activated, which will prevent thrombin from forming. Based on Table 1, what percent of the life cycle of yeast cells is spent in DNA replication? A. 5 percent C. 25 percent Based on the sample means, which of the following conclusions about the cells in the growing root tips of Zea mays seedlings is best supported by the results of the experiment? A. The cells of the root tips grow to larger sizes when the seedlings are planted in compact sand than when the seedlings are planted in loose sand. D. More cells are produced per unit of time in the root tips growing in compact sand than in the root tips growing in loose sand. Based on Figure 1, which of the following statements correctly links a stage of the cell cycle with the event occurring at that stage? A. Stage II
represents the G2 phase of the cell cycle. B. Synthesis of sufficient DNA for two daughter cells occurs in stage IIII. Which of the following statements is consistent with the data in Figure 1? A. The cells have a haploid
chromosome number of 3. C. There is a change from 3 to 6 picograms of DNA because DNA is replicated before each round of cell division. Which of the following most accurately describes an observation and an effect of the viral infection indicated by the data in Table 1? A. Normal cells spend 98 percent of their time cycling in and out of interphase. The virus reduces this to 5 percent of the time. D. Seventy-five percent of the virus-infected cells are found in mitosis. The virus stimulates frequent cell division. Based on the data, the percent of the mitotic cells that were in metaphase is closest to which of the following? A.
5% C. 18% The epidermal growth factor receptor EGFR is a cell surface receptor. When a growth factor binds to EGFR, the receptor is activated. The activated EGFR triggers a signal transduction pathway, which leads to increased frequency of cell division. A. Increased apoptosis will lead to abnormal growth of the tissue. B. Increased cell division will lead to the formation of a tumor. The tumor suppressor protein p53 binds to DNA and activates target
genes, which results in the synthesis of p21, CD95, and other proteins. The p21 protein promotes cell-cycle arrest, whereas the CD95 protein promotes apoptosis. A. Rapid cell growth without cell division C. Uncontrolled cell proliferation Which statement best predicts why a cell's progression through the cell cycle might be halted at the G1/S checkpoint? A. Spindle fibers have not correctly attached to chromosomes. B. There are not enough nucleotides available to construct new DNA When epinephrine binds to cardiac (heart) muscle cells, it speeds up their contraction. When it binds to muscle cells of the small intestine, it inhibits their contraction. How can the same hormone have different effects on muscle cells? a. Cardiac cells have more receptors for epinephrine than do intestinal cells. c. The two types of muscle cells have different signal transduction pathways for epinephrine and thus have different cellular responses. A signal molecule that binds to a plasma-membrane protein functions as a a. Ligand How do receptor tyrosine kinases transduce a signal? a. They transport the signal molecule into the cell, where it binds to and activates a transcription factor. The transcription factor then alters gene expression. e. They form a dimer; they phosphorylate each other's tyrosoines; specific proteins bind to and are activated by these phosphorylated tyrosines. Which of the following can activate a protein by transferring a phosphate group to it? a. cAMP d. Protein kinase Many signal transduction pathways use second messengers to a. Transport a signal
through the lipid bilayer portion of the plasma membrane c. Relay the message from the inside of the membrane throughout the cytoplasm. Signal amplification is most often achieved by a. An enzyme cascade involving multiple protein kinases. a. An enzyme cascade involving multiple protein kinases. Which of the following is incorrectly matched with its description? a. Scaffolding protein- large relay protein that may bind with several other relay proteins to increase the efficiency of a signaling pathway. b. Protein phosphatase- enzyme that transfers a phosphate group from ATP to a protein, causing a conformational change that usually activates the protein. Based on Figure 1, which of the following statements best describes the epinephrine pathway? a. It involves the opening and closing of ion channels. b. It involves enzymes activating other enzymes. Which of the following statements best describes the role of adenyl cyclase in the epinephrine signaling pathway? a. It converts a polymer to its monomer subunits. c. It accelerates the production of a second messenger. A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the researcher's claim? a. Epinephrine is a signaling molecule that binds to a transmembrane protein. d. Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate. In a certain signal transduction pathway, the binding of an extracellular molecule to a cell-surface protein results in a rapid increase in the concentration of cyclic AMP inside the cell. The cyclic AMP binds to and activates cytosolic enzymes that then activate other enzymes in the cell. Which of the following statements best describes the role of cyclic AMP in this pathway? a. It acts as the
signaling molecule that passes the signal from the cell to other cells. c. It acts as a second messenger that helps relay and amplify the signal within the cell. Air is less dense at very high elevations, so less oxygen is available than in the denser air at sea level. Based on the model in figure 1, if a person travels from sea level to a high elevation location, which of the following correctly predicts the response to the decreased blood oxygen level? a. More erythropoietin will be secreted from the kidneys, decreasing production of erythrocytes. b. More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes. Which of the following best describes how the amount of DNA in the cell
changes during M phase? d. The amount of DNA is halved as the cell divides into two daughter cells. Sister chromatids a. have
one-half the amount of genetic material as does the original chromosome. c. each have their own kinetochore. Which of the following would not be exhibited by cancer cells? a.
changing levels of MPF concentration c. density-dependent inhibition A cell that passes the restriction point in G1 will most likely a. undergo chromosome duplication. a. undergo chromosome duplication. The rhythmic changes in cyclin concentration in a cell cycle are due to a. its increased production once the restriction point is passed. c. its degradation, which is initiated by active MPF. What is the expected percent change in DNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of G1 phase to the end of G2 phase? a. -100% d. +100% Figure 1, what percent of the time required to complete a full cycle do the cells typically spend in interphase?(G1-9hrs, S- 7hrs, G2- 3 hrs, M- 1hr) a. 5% d. 95% Which of the following best predicts the effect of the mutation?Which of the following best predicts the effect of a mutation that causes EGFR to be active in the absence of a growth factor? Increased cell division will lead to the formation of a tumor.
Which of the following outcomes will most likely result from the irreversible binding of GDP to the G protein quizlet?Which of the following outcomes will most likely result from the irreversible binding of GDP to the G protein? The intracellular concentration of glycogen will increase.
Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the target cells in the body?Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the target cells in the body? The hormone is released into the bloodstream where it can be transported to all cells with the correct receptors.
Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 pm?Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 p.m.? Immediately after the meal, the blood glucose level will decrease because of the increase in glucagon levels.
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