Practice Questions ch. 16 and 20 PDF

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Chapter 16 – Practice Exam Questions 1. When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________. a. neurotransmitter. b. hormone. c. dissolved gas. d. scaffold. 2. Which of the following statements is false? a. Nucleotides an...

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Chapter 16 – Practice Exam Questions 1. When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________. a. neurotransmitter. b. hormone. c. dissolved gas. d. scaffold. 2. Which of the following statements is false? a. Nucleotides and amino acids can act as extracellular signal molecules. b. Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription. c. Some signal molecules are transmembrane proteins. d. Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids. 3. 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. 4. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? a. a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO b. a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP c. a muscle cell that has cyclic GMP phosphodiesterase constitutively active d. a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO 5. Which of the following statements about molecular switches is false? a. Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. b. Protein kinases transfer the terminal phosphate from ATP onto a protein. c. Serine/threonine kinases are the most common types of protein kinase. d. A GTP-binding protein exchanges its bound GDP for GTP to become activated.

6. 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. parcrine c. neuronal d. contact-dependent 7. Which of the following statements about G-protein-coupled receptors (GPCRs) is false? (a) GPCRs are the largest family of cell-surface receptors in humans. (b) GPCRs are used in endocrine, paracrine, and neuronal signaling. (c) GPCRs are found in yeast, mice, and humans. (d) The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains. 8. Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is false? (a) Heart muscle cells decrease their rate and force of contraction when they receive acetylcholine, whereas skeletal muscle cells contract. (b) Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family. (c) Active acetylcholine receptors on salivary gland cells and heart muscle cells activate different intracellular signaling pathways. (d) Heart muscle cells, salivary gland cells, and skeletal muscle cells all respond to acetylcholine within minutes of receiving the signal. 9. All members of the steroid hormone 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. 10. Which of the following statements is true? (a) Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal. (b) The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. (c) Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism. (d) The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells.

A protein kinase can act as an integrating device in signaling if it ___________________. (a) phosphorylates more than one substrate. (b) catalyzes its own phosphorylation. (c) is activated by two or more proteins in different signaling pathways. (d) initiates a phosphorylation cascade involving two or more protein kinases. The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by ________________. (a) activating a G protein. (b) activating a receptor tyrosine kinase. (c) diffusing into cells and stimulating the cyclase directly. (d) activating an intracellular protein kinase. The length of time a G protein will signal is determined by _______. (a) the activity of phosphatases that turn off G proteins by dephosphorylating Gα. (b) the activity of phosphatases that turn GTP into GDP. (c) the degradation of the G protein after Gαseparates from Gβγ (d) the GTPase activity of Gα The following happens when a G-protein-coupled receptor activates a G protein. (a) The β subunit exchanges its bound GDP for GTP. (b) The GDP bound to the α subunit is phosphorylated to form bound GTP. (c) The α subunit exchanges its bound GDP for GTP. (d) It activates the α subunit and inactivates the βγ complex. 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 the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid When Ras is activated, cells will divide. A dominant-negative form of Ras clings too tightly to GDP. You introduce a dominant-negative 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 extracellular signals that typically activate Ras. (d) The normal Ras in the cells you create will not be able to bind GDP because the dominantnegative Ras binds to GDP too tightly.

Which of the following mechanisms is not directly involved in inactivating an activated RTK? (a) dephosphorylation by serine/threonine phosphatases (b) dephosphorylation by protein tyrosine phosphatases (c) removal of the RTK from the plasma membrane by endocytosis (d) digestion of the RTK in lysosomes A protein kinase can_______________. a. be the receptor for a hormone b. convert ATP to cAMP c. directly activate G proteins d. decrease the cytosolic calcium level e. be inhibited by a phosphorylation by other proteins GPCRs are often referred to as seven-pass transmembrane receptors because they have: a. seven pores that signal molecules can use to pass through the bilayer b. seven receptor on each side of the lipid bilayer that receives and transmit signals. c. seven different G proteins with which they interact to amplify signals d. a polypeptide chain that crosses the lipid bilayer seven times. Cyclic AMP is a. an allosteric regulator of Ga b. an allosteric regulator of PKA c. an allosteric regulator of phosphodiesterase d.an allosteric regulator of protein kinase B e. an allosteric regulator of phosphodiesterase C Tyrosine kinase receptor can activate the enzyme P13K , which phosphorylated inositol phospholipids. These phospholipids then: a. serves as phosphate donors in phosphorylation reactions b. activates Ras c. serves as docking sites that recruit intracellular PH domain contain signaling proteins to the plasma membrane d. activates G proteins c. serves as docking sites that recruit intracellular PH domain contain signaling proteins to the plasma membrane G protein-linked receptors interact with G proteins________. (a). with the G protein binding domain adjacent to the cytosol-exposed segment between two sets of helices (b). with the G protein binding domain directly adjacent to the ligand-binding site when the receptor binds GTP (c). with the membrane spanning region of the receptor most distant from the ligand-binding αhelices (d). with the membrane-spanning region of the G protein adjacent to the ligand-binding α-helices

During G-protein activation, _______ binds _______, thus become activated A. Gα; GTP B. Gβ; GTP C. Gα; ATP D. Gβ; GDP E. Gα; GDP Tyrosine-kinase receptors ____. (a). bind to nonpolar signal molecules such as NO and steroids (b). enzymatically hydrolyze the signal molecule shortly after its arrival (c). enzymatically degrade GTP to GDP (d). directly allow specific ions to enter the cell after ligand binding (e). send signals though recruiting SH2 domain proteins During Ras activation, ____ binds _____. A. B. C. D.

Ras; GTP RasGEF; ATP RasGEF; GDP RasGap; GTP

The PDGFR is a typical receptor tyrosine kinase. Therefore, it does ________. (a). require G proteins (b). bind to proteins with PH domains (c). have seven transmembrane domains (d) form a dimer Paracrine hormones ________. (a). include androgens and estrogens (b). include epinephrine and norepinephrine (c). are stable for long periods (d). act locally e). act over large distances Which if the following proteins contain switch helix? (a). phospholipase (b). MAP kinase (c). Ras (d). Albumin (e). tyrosine-kinase receptors

The binding of ________ to endothelial cells triggers the production of ________, which leads to muscle relaxation. (a). histamine; nitric oxide (b). acetylcholine; calcium (c). somatotropin; growth factors (d). histamine; calcium (e). acetylcholine; nitric oxide

You have been assigned to identify a novel purified protein in your lab. You immediately notice this protein contains a polypeptide chain that traverses the membrane seven times and the transmembrane portion of the protein consist of alpha helices. What can you conclude about this protein? a)it belongs to the family of G-protein coupled receptors b)it belongs to the cyclin dependent kinase family c)it belongs to the receptor tyrosine kinase family d) it belongs to the enzyme-coupled receptor proteins e)it belongs to the integrin family of cell membrane proteins Mitogens are____. a)extracellular signals that stimulate cell division b)transcription factors important for cyclin production c)kinases that cause cells to grow in size d)produced by mitotic cells to keep nearby neighboring cells from dividing The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? (a) a mutation that prevents dimerization of the receptor (b) a mutation that destroys the kinase activity of the receptor (c) a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor (d) a mutation that prevents the binding of the normal extracellular signal to the receptor Chapter 20 – Cancer A malignant tumor is more dangerous than a benign tumor because ______________________. (a) its cells are proliferating faster. (b) it causes neighboring cells to mutate. (c) its cells attack and phagocytose neighboring normal tissue cells. (d) its cells invade other tissues.

A metastasis is _________. (a) a secondary tumor in a different part of the body that arises from a cell from the primary tumor (b) a cell that is dividing in defiance of normal constraints. (c) a part of the primary tumor that has invaded the surrounding tissue. (d) the portion of the cancerous tumor that displays genetic instability. Which of the following statements about cancer is false? (a) Viruses cause some cancers. (b) Tobacco use is responsible for more than 20% of all cancer deaths. (c) A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell. (d) Chemical carcinogens cause cancer by changing the nucleotide sequence of DNA. Which of the following genetic changes cannot convert a proto-oncogene into an oncogene? (a) A mutation that introduces a stop codon immediately after the codon for the initiator methionine. (b) A mutation within the coding sequence that makes the protein hyperactive. (c) An amplification of the number of copies of the proto-oncogene, causing overproduction of the normal protein. (d) A mutation in the promoter of the proto-oncogene, causing the normal protein to be transcribed and translated at an abnormally high level. Which of the following statements about tumor suppressor genes is false? (a) Gene amplification of a tumor suppressor gene is less dangerous than gene amplification of a proto-oncogene. (b) Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells. (c) Inactivation of tumor suppressor genes leads to enhanced cell survival and proliferation. (d) Individuals with only one functional copy of a tumor suppressor gene are more prone to cancer than individuals with two functional copies of a tumor suppressor gene. Ras is a GTP-binding protein that is often defective in cancer cells. A common mutation found in cancer cells causes Ras to behave as though it were bound to GTP all the time, which will cause cells to divide inappropriately. From this description, the normal Ras gene is _______. (a) a tumor suppressor. (b) an oncogene. (c) a proto-oncogene. (d) a gain-of-function mutation.

APC is a tumor suppressor and acts in the Wnt signaling pathway to prevent the TCF complex from turning on Wnt-responsive genes. Mice that lack the gene encoding TCF4 do not have the ability to maintain the pool of proliferating gut stem cells needed to renew the gut lining. What do you predict will happen in mice that lack the APC gene? (a) Mice lacking the APC gene will be like the mice lacking TCF4 and not be able to renew the gut lining. (b) Mice lacking the APC gene will have inappropriate proliferation of gut stem cells. (c) Mice lacking the APC gene will have a hyperactive Wnt receptor even though there is no Wnt signal. (d) Mice lacking the APC gene will be like normal healthy mice, since APC is a tumor suppressor and thus not needed unless there is a tumor present. What is the difference between a malignant and benign tumor? A. A malignant tumor proliferates in defiance of normal constraints, while a benign tumor does not B. A malignant tumor invades and colonizes other tissues, while a benign tumor does not C. A benign tumor can be treated while a malignant tumor cannot be treated. Cancer is fundamentally which type of disease? A. A genetic disease B. A disease of obesity C. An environmental disease D. An infectious disease Which of the following is NOT a key behavior of cancer cells? A. They have a reduced dependence on signals from other cells for their growth, survival, and division B. They are less prone than normal cells to kill themselves by apoptosis C. They can often proliferate indefinitely D. Most are genetically unstable, with a greatly increased mutation rate E. They are abnormally invasive F. They digest neighboring cells to fuel proliferation G. They can often survive and proliferate in foreign tissues to form secondary tumors. A single mutation can activate which class of cancer causing gene? A. DNA repair gene B. Oncogene C. Tumor suppressor gene Many of the genes mutated in individual tumors fall under which of the following regulatory pathways? A. Pathways governing the initiation of cell division B. Pathways controlling cell growth C. Pathways regulating the cellular response to DNA damage or stress D. All the above

Part II – Fill In Given the generic signaling pathway in Figure Q16-12, write the number corresponding to the item on the line next to the description below.

___2____ receptor protein ____4____ effector proteins ____3____ intracellular signaling proteins ____1___ ligand

Match the class of cell-surface receptor with the best description of its function. Not all descriptors will be used. G-protein-coupled receptors __D___ ion-channel-coupled receptors __A___ enzyme-coupled receptors ___E___ A. alter the membrane potential directly by changing the permeability of the plasma membrane B. signal by opening and closing in a ligand-independent manner C. must be coupled with intracellular monomeric GTP-binding proteins D. all receptors of this class are polypeptides with seven transmembrane domains E. discovered for their role in responding to growth factors in animal cells

Rank the following types of cell signaling from 1 to 4, with 1 representing the type of signaling in which the signal molecule travels the least distance and 4 the type of signaling in which the signal molecule travels the largest distance. __3___ paracrine signaling __1__ contact-dependent signaling __2__ neuronal signaling __4___ endocrine signaling

Circle the phrase in each pair that is likely to occur more rapidly in response to an extracellular signal. A. Changes in cell secretion / increased cell division B. Changes in protein phosphorylation / changes in proteins being synthesized C. Changes in mRNA levels / changes in membrane potential

Match the target of the G protein with the appropriate signaling outcome. adenylyl cyclase ___B____ ion channels ___C_____ phospholipase C ____A____ A. cleavage of inositol phospholipids B. increase in cAMP levels C. changes in membrane potential

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