PCB 3023C / PCB3023C Exam 3: (Latest Update 2026 / 2027) Cell Biology | Questions & Answers | Exam study material | 100% Correct - FGCU

PCB 3023C / PCB3023C Exam 3: (Latest Update 2026 / 2027) Cell Biology | Questions & Answers | Exam study material | 100% Correct - FGCU PCB 3023 Exam 2026 / 2027 Academic Year Q: Which of these processes require a membrane? Choose one or more: A) generation of ATP by photosynthesis in plants B) generation of ATP by photosynthesis in bacteria C) generation of energy by mitochondria D) generation of ATP by oxidative phosphorylation E) generation of ATP by glycolysis A) generation of ATP by photosynthesis in plants B) generation of ATP by photosynthesis in bacteria C) generation of energy by mitochondria D) generation of ATP by oxidative phosphorylation Q: In the electron-transport chain, as electrons move along a series of carriers, they release energy that is used to do what?Choose one: A) phosphorylate ADP to form ATP B) hydrolyze ATP C) oxidize food molecules D) split water into protons and oxygen E) pump protons across a membrane E) pump protons across a membrane Q: Now, where do you find an electron to give to the original low-energy electron donor (the first one in the row)? A. take a low energy electron from water B. take a high energy electron from water C. take a low energy electron from NADPH D. take a high energy electron from NADPH E. return the high energy electron from reduced acceptor A. take a low energy electron from water Q: In the light reactions of photosynthesis, a proton gradient is generated which drives ATP synthesis. Where do protons become concentrated in the chloroplast? A. stroma B. thylakoid space C. inner membrane D. thylakoid membrane E. cytosol B. thylakoid space Q: Which of the following statements is true? A. The light-independent reactions of photosynthesis occur only in the absence of light. B. Each round of the Calvin cycle uses five molecules of CO2 to produce one molecule of glyceraldehyde 3-phosphate and one of pyruvate. C. Ribulose 1,5-bisphosphate is similar to oxaloacetate in the Citric acid cycle in that they are both regenerated at the end of their respective cycles. C. Ribulose 1,5-bisphosphate is similar to oxaloacetate in the Citric acid cycle in that they are both regenerated at the end of their respective cycles. Q: Which could be the activated intermediate in the dehydration synthesis forming a phosphodiester bond? A. P, B. AMP C. ADP D. ATP D. ATP Q: Figure 14–38 illustrates the pathway of electron flow in photosynthesis. In an alternative pathway of photosynthesis, called cyclic photophosphorylation, electrons from photosystem I are passed to ferredoxin and are then transferred back to plastoquinone. Which of the following would be expected to result from cyclic photophosphorylation? A. Electrons from cyclic photophosphorylation will be returned to the reaction center chlorophyll molecules of photosystem II, preventing the need to split water and reducing the production of molecular oxygen. B. Electrons from cyclic photophosphorylation will be used to pump protons into the thylakoid lumen, leading to production of additional ATP. C. Electrons from cyclic photophosphorylation will be used to reduce NADP+ to NADPH. D. Cyclic photophosphorylation will require the splitting of additional water molecules, resulting in the production of more molecular oxygen. B. Electrons from cyclic photophosphorylation will be used to pump protons into the thylakoid lumen, leading to production of additional ATP. Q: What is true of the organelles that produce ATP in eukaryotic animal cells?Choose one: A) They evolved from bacteria engulfed by ancestral cells billions of years ago. B) They reproduce sexually.They harbor eukaryotic-like biosynthetic machinery for making RNA and protein. C) They contain the same genes as the chloroplasts of plant cells. D) They have a separate set of DNA that contains many of the same genes found in the nucleus. A) They evolved from bacteria engulfed by ancestral cells billions of years ago. Q: In additions to chlorophylls, chloroplasts also contain accessory pigments. These pigments help to capture light of wavelengths not readily captured by chlorophylls. In addition, some pigments are also anti-oxidant molecules and protect the photosystems from oxidative damage caused by high intensity light. Using the chlorophyll a absorbance spectrum shown in Figure 14–31, determine which of the following pigments has an absorbance that MOST overlaps with the absorbance of chlorophyll a?Figure 14–31 Choose one: A. Oenin (an anthocyanin pigment): peak absorbance range ~450–550 nm B. Phycoerythrin (a phycobilin pigment): peak absorbance range ~500–575 nm C. β-Carotene (a carotenoid pigment): peak absorbance range ~400–500 nm D. Betanin (a betalain pigment): peak absorbance range ~475–575 nm C. β-Carotene (a carotenoid pigment): peak absorbance range ~400–500 nm Q: Stage 1 of photosynthesis is, in large part, equivalent to what process?Choose one: A) glycolysis B) oxidative phosphorylation C) the carbon-fixation cycle D) the production of acetyl CoA by the pyruvate dehydrogenase complexthe citric acid cycle B) oxidative phosphorylation Q: In the electron-transport chain in chloroplasts, which molecule serves as the final electron acceptor?Choose one: A) ADP B) H2O C) NAD+ D) O2 E) NADP+ E) NADP+ Q: Which of these is able to boost electrons to the very high energy level needed to make NADPH from NADP+?Choose one: A) photosystem I B) ATP synthase C) H2O D) photosystem II E) cytochrome b6-f complex A) photosystem I Q: In photosynthesis, what drives the generation of ATP by ATP synthase?Choose one: A) the transfer of high-energy electrons to ATP synthase B) a proton gradient across the thylakoid membrane C) the phosphorylation of ATP synthase D) the absorption of light by a photosynthetic reaction center E) the generation of a charge separation in the photosynthetic reaction center B) a proton gradient across the thylakoid membrane Q: During stage I of photosynthesis, excited electrons move in which direction?Choose one: A) from the stroma to the thylakoid membrane to the thylakoid space B) from the chlorophyll special pair to an electron carrier to NADP+ C) from NADPH to a mobile electron carrier to the chlorophyll special pair D) from sunlight to the chlorophyll special pairfrom an electron carrier to NADP+ to ATP synthase B) from the chlorophyll special pair to an electron carrier to NADP+ Q: Which photosystem is depicted in this simplified diagram?Choose one: A) either photosystem I or II B) More information is needed to determine which photosystem is depicted. C) photosystem I D) photosystem II D) photosystem II Q: Which photosystem is depicted in this simplified diagram?Choose one: A) either photosystem I or II B) More information is needed to determine which photosystem is depicted. C) photosystem I D) photosystem II C) photosystem I Q: During photosynthesis, what happens in the water-splitting step?Choose one: A) It is catalyzed by an enzyme containing an iron–sulfur cluster. B) It consumes protons and thereby depletes the proton gradient across the thylakoid membrane. C) It takes place during stage 2 of photosynthesis. D) It generates essentially all of the O2 in the Earth's atmosphere. E) It occurs on the stromal side of the thylakoid membrane. D) It generates essentially all of the O2 in the Earth's atmosphere. Q: Which photosystem is depicted in this simplified diagram?Choose one: A) either photosystem I or II B) More information is needed to determine which photosystem is depicted. C) photosystem I D) photosystem II D) photosystem II Q: As the human population grows, it becomes increasingly important to maximize crop yields. As such, scientists search for more efficient ways for plants to convert CO2 into biomass. One approach is to genetically modify plant enzymes involved in photosynthesis to increase their efficiency. Which plant enzyme, directly responsible for carbon fixation, is a focus of research? Choose one: A. ATP synthase B. cytochrome c oxidase C. chlorophyll D. Rubisco D. Rubisco Q: What is true of the process of combining CO2 and H2O to make a carbohydrate?Choose one: A) It is energetically favorable. B) It is energetically unfavorable. C) It occurs only during daylight hours. D) It takes place in all eukaryotic cells. E) It produces ATP. B) It is energetically unfavorable. Q: What provides the fuel to convert CO2 into sugars in chloroplasts?Choose one: A) Nothing; the reactions do not require energy. B) a proton gradient across a membrane C) ATP generated by cell respiration D) oxidation of food molecules E) ATP and NADPH generated in the photosynthetic light reactions E) ATP and NADPH generated in the photosynthetic light reactions Q: Which is true of the carbon-fixation (Calvin) cycle?Choose one or more: A) It produces CO2. B) It regenerates energy-rich ribulose 1,5-bisphosphate. C) It produces O2. D) It produces NADPH and ATP. E) It requires energy-rich ribulose 1,5-bisphosphate. F) It requires CO2. G) It requires O2. H) It requires NADPH and ATP. B) It regenerates energy-rich ribulose 1,5-bisphosphate. E) It requires energy-rich ribulose 1,5-bisphosphate. F) It requires CO2. H) It requires NADPH and ATP. Q: For every three molecules of CO2 that enter the carbon-fixation cycle, what is produced and what is consumed?Choose one: A) 3 molecules of glyceraldehyde 3-phosphate are produced, and 9 molecules of ATP + 6 molecules of NADPH are consumed. B) 6 molecules of glyceraldehyde 3-phosphate are produced, and 6 molecules of ATP + 9 molecules of NADPH are consumed. C) 1 molecule of glyceraldehyde 3-phosphate is produced, and 9 molecules of ATP + 6 molecules of NADPH are consumed. D) 1 molecule of glyceraldehyde 3-phosphate is produced, and 9 molecules of ATP + 12 molecules of NADPH are consumed. E) 1 molecule of glyceraldehyde 3-phosphate is produced, and 6 molecules of ATP + 9 molecules of NADPH are consumed. C) 1 molecule of glyceraldehyde 3-phosphate is produced, and 9 molecules of ATP + 6 molecules of NADPH are consumed. Carbon fixation occurs in the second stage of photosynthesis, during the light-independent reactions of the Calvin cycle. In the first step of this cycle, the enzyme Rubisco adds CO2 to the energy-rich compound ribulose 1,5-bisphosphate, ultimately producing two molecules of 3 phosphoglycerate. In a culture of green alga that is carrying out photosynthesis in the presence of CO2 in the laboratory, what would happen to the levels of ribulose 1,5-bisphosphate and 3 phosphoglycerate in the minutes after the lights were turned off and the cultures were plunged into darkness?Choose one: A) Ribulose 1,5-bisphosphate would be depleted, but 3-phosphoglycerate would accumulate. B) Nothing would happen because the Calvin cycle is not light-dependent. C) Ribulose 1,5-bisphosphate would accumulate, but 3-phosphoglycerate would be depleted. D) Both would accumulate. E) Both would be depleted. A) Ribulose 1,5-bisphosphate would be depleted, but 3-phosphoglycerate would accumulate. During very active periods of photosynthesis, the glyceraldehyde 3-phosphate generated by carbon fixation in the chloroplast stroma is stored as which molecule?Choose one: A) CO2 B) pyruvate C) glycogen D) ATP E) starch E) starch How can the glyceraldehyde 3-phosphate produced in the carbon-fixation cycle be used?Choose one or more: A) It can be converted into fat and stored in the chloroplast stroma. B) It can be consumed by the carbon-fixation cycle to produce ribulose 1,5-bisphosphate. C) It can be converted into starch and stored in the chloroplast stroma. D) It can be converted into sucrose in the chloroplast stroma. C) It can be fed into the citric acid cycle in the chloroplast stroma. A) It can be converted into fat and stored in the chloroplast stroma. B) It can be consumed by the carbon-fixation cycle to produce ribulose 1,5-bisphosphate. C) It can be converted into starch and stored in the chloroplast stroma. When a chlorophyll molecule captures light energy, what form does the energy take?Choose one: A) formation of a high-energy bond in ATP in the thylakoid membrane B) release of the chlorophyll's hydrophobic tail C) transfer of high-energy electrons to the porphyrin ring D) excitation of electrons in the porphyrin ring E) oxidation of magnesium within the porphyrin ring D) excitation of electrons in the porphyrin ring During photosynthesis, charge separation takes place when which of the following occurs?Choose one: A) The special pair passes an electron to an electron carrier in the antenna complex, leaving behind a positive charge. B) The special pair passes an electron to an electron carrier in the antenna complex, leaving behind a negative charge. C) The special pair passes an electron to an electron carrier in the reaction center, leaving behind a negative charge. D) Energy jumps randomly from one chlorophyll molecule to another in the antenna complex. E) Light energy is captured by a chlorophyll molecule in the antenna complex. F) The special pair passes an electron to an electron carrier in the reaction center, leaving behind a positive charge. F) The special pair passes an electron to an electron carrier in the reaction center, leaving behind a positive charge. What is true of the antenna complex of a photosystem?Choose one: A) It converts light energy into chemical energy. B) It passes electrons to a photosynthetic electron transport chain. C) It extracts electrons from water. D) It captures light energy. E) It includes a special pair of chlorophylls. D) It captures light energy. Once excited by sunlight, chlorophylls in the antenna complex do which of the following?Choose one: A) release that energy as heat B) reflect the energy as light C) transfer electrons to the chlorophyll special pair D) transfer the energy to the chlorophyll special pair E) transfer protons to the chlorophyll special pair D) transfer the energy to the chlorophyll special pair What is true of stage 2 of photosynthesis?Choose one: A) It takes place in the chloroplast grana. B) It produces all of the O2 we breathe. C) It generates a proton gradient across the thylakoid membrane. D) It produces glyceraldehyde 3-phosphate in the stroma. E) It begins with the production of ATP and NADPH and ends with their consumption. D) It produces glyceraldehyde 3-phosphate in the stroma. In eukaryotic cells, where does the conversion of CO2 and H2O to sugar take place?Choose one: A) mitochondrial matrix B) chloroplast stroma C) thylakoid membrane D) plasma membrane E) cytosol B) chloroplast stroma Photosynthesis allows plants to capture energy from sunlight to produce what?Choose one: A) H2O B) NADH C) chlorophyll D) CO2 E) sugars E) sugars In chloroplasts, the pigment chlorophyll donates electrons to an electron-transport chain in which cellular compartment?Choose one: A) mitochondrial inner membrane B) thylakoid membrane C) inner membrane of the chloroplast envelope D) plasma membrane E) stroma B) thylakoid membrane Chlorophyll molecules absorb which color of light most strongly?Choose one: A) red B) green C) black D) white E) UV A) red During Earth’s history, with the rise of cyanobacteria, what molecule began accumulating in the atmosphere for the first time?Choose one: A) H2O B) CO2 C) O2 D) N2 C) O2 What electron acceptor allows an organism to completely break down organic molecules into CO2 and H2O and thereby release a large amount of energy that can be harnessed by the cell to do work?Choose one: A) NADH B) pyruvate C) H2O D) O2 E) H2S D) O2 What is true of nitrogen fixation?Choose one: A) It promoted the evolution of ancient cells by allowing them to convert N2 to NO2 near thermal vents. B) It reduces N2 to ammonia (NH3). C) It can be used to generate an H+ gradient. D) It converts CO2 and H2O into sugars. E) It requires a small energy input and is thus energetically favorable. B) It reduces N2 to ammonia (NH3). Shown here is the mechanism believed to be used for pumping protons by cytochrome c oxidase across the inner mitochondrial membrane. One of the steps shown is unidirectional because it is driven by the energy of electron transport. Why must this step be performed only in one direction?Choose one: A. The protons could be also captured from the intermembrane space and released back into the matrix. B. The inner membrane would become porous to all molecules. C. The complex would stay stuck in the closed (center conformation). D. The H+ affinity in the two conformations would reverse. A. The protons could be also captured from the intermembrane space and released back into the matrix. In oxidative phosphorylation in mitochondria, high-energy electrons are transferred to the electron transport chain from activated carriers like NADH. Stage 1 of photosynthesis also uses an electron transport chain to pump protons and make ATP. In this case, where do the high-energy electrons come from?Choose one: A. NADPH B. chlorophyll C. FADH2 D. ADP B. chlorophyll The outer membrane of the nucleus is continuous with the membrane of which other organelle?Choose one: A. mitochondrion B. Golgi apparatus C. endoplasmic reticulum D. endosome E. peroxisome C. endoplasmic reticulum Which organelle is the major site of new membrane synthesis in a cell?Choose one: A) nucleus B) endoplasmic reticulum C) Golgi apparatus D) mitochondrion E) peroxisome B) endoplasmic reticulum Which organelle receives proteins and lipids from the endoplasmic reticulum, modifies them, and then dispatches them to other destinations in the cell?Choose one: A) endosome B) nucleus C) Golgi apparatus D) peroxisome E) mitochondrion C) Golgi apparatus How do the interiors of the ER, Golgi apparatus, endosomes, and lysosomes communicate with each other?Choose one: A. by excreting hormones and other small signaling molecules B. by fusing with one another C. by open pores that allow ions to exit and enter the organelles D. by small vesicles that bud off of one organelle and fuse with another E. They do not communicate with one another. D. by small vesicles that bud off of one organelle and fuse with another Which membrane-enclosed organelles most likely evolved in a similar manner?Choose one: A) mitochondria and the ER B) mitochondria and the nucleus C) mitochondria and the Golgi apparatus D) chloroplasts and peroxisomes E) the nucleus and the ER E) the nucleus and the ER In muscle cells, which organelle sequesters Ca2+ from the cytosol?Choose one: A) lysosome B) rough ER C) mitochondrion D) smooth ER E) endosome D) smooth ER In a typical human secretory cell, which of the following membranes has the largest surface area?Choose one: A) lysosome B) rough ER C) nuclear inner membrane D) smooth ER E) plasma membrane B) rough ER Proteins that lack a sorting signal remain as permanent residents of which part of a eukaryotic cell?Choose one: A) cytosol B) ER C) proteasome D) nucleus E) Golgi apparatus A) cytosol What would happen to a protein that is engineered to contain both a nuclear localization signal and a nuclear export signal?Choose one: A) It would shuttle in and out of the nucleus. B) It would bind to nuclear import receptors and nuclear export receptors, forming a nonfunctional complex. C) It would spend most of its time in the cytosol. D) It would spend most of its time in the nucleus. E) It would be unable to fold properly and would be targeted for destruction. A) It would shuttle in and out of the nucleus. Which proteins bind to nuclear localization signals on newly synthesized proteins?Choose one: A) nuclear import receptors B) nuclear pore proteins C) nuclear export receptors D) signal-recognition particles (SRPs) E) cytosolic fibrils A) nuclear import receptors Which of these actions occur(s) commonly at a nuclear pore complex?Choose one or more: A) mRNA molecules are exported to the cytosol. B) Proteins with a nuclear localization signal enter at the same time that proteins with a nuclear export signal exit. C) Small water-soluble molecules are selectively transported into the nucleus. D) Protein complexes diffuse into the nucleus. E) Nuclear import receptors are exported to the cytosol. F) Nuclear import receptors enter from the cytosol. A) mRNA molecules are exported to the cytosol. B) Proteins with a nuclear localization signal enter at the same time that proteins with a nuclear export signal exit. E) Nuclear import receptors are exported to the cytosol. F) Nuclear import receptors enter from the cytosol. Proteins destined for the Golgi apparatus, endosomes, lysosomes, and even the cell surface must pass through which organelle?Choose one: A) mitochondrion B) peroxisome C) ER D) nucleus C) ER Which is true of ribosomes?Choose one: A) Polyribosomes translate only cytosolic proteins. B) A special class of ribosomes attached to the ER membrane translates the proteins destined for that organelle. C) A common pool of ribosomes is used to synthesize both cytosolic proteins and proteins destined for the ER. D) All ribosomes are attached to the ER when they begin synthesizing a protein. E) Polyribosomes translate only those proteins that have an ER signal sequence. C) A common pool of ribosomes is used to synthesize both cytosolic proteins and proteins destined for the ER. As a polypeptide is being translocated across the membrane of the endoplasmic reticulum, a stop transfer sequence can halt the process. What eventually becomes of this stop-transfer sequence?Choose one: A) It is translocated into the lumen of the endoplasmic reticulum. B) It stops protein synthesis and causes the ribosome to be released back to the cytosol. C) It is cleaved from the protein. D) It remains in the cytosol. E) It forms an α-helical membrane-spanning segment of the protein. E) It forms an α-helical membrane-spanning segment of the protein. The ER signal sequence on a growing polypeptide chain is recognized by a signal-recognition particle (SRP) in the cytosol. What does this interaction accomplish?Choose one: A) It cleaves the ER signal sequence from the polypeptide chain. B) It returns the ribosome to the pool of free ribosomes in the cytosol. C) It guides the ribosome and its polypeptide to the ER. D) It releases the polypeptide chain from the ribosome. E) It speeds the synthesis of the polypeptide chain. C) It guides the ribosome and its polypeptide to the ER. Which of these statements is true?Choose one: A) The N-terminus of a protein translocated into the ER will always remain in the ER lumen. B) Membrane-bound ribosomes and free ribosomes are structurally and functionally identical; they differ only in the proteins they are making at a particular time. C) The signal sequence that directs a growing polypeptide chain to enter the ER membrane is always removed by a transmembrane signal peptidase. D) Attachment to a polyribosome prevents a growing polypeptide chain from being translocated into the ER. E) Only those proteins that are destined to remain inserted in the membrane are made on the rough ER; soluble proteins are made in the cytosol. B) Membrane-bound ribosomes and free ribosomes are structurally and functionally identical; they differ only in the proteins they are making at a particular time. Which organelle cannot receive proteins directly from the cytosol?Choose one: A) mitochondrion B) nucleus C) chloroplast D) Golgi apparatus E) peroxisome D) Golgi apparatus What is the source of energy for protein translocation into the ER?Choose one: A) hydrolysis of ATP by the translocator B) the action of chaperones C) hydrolysis of ATP by the SRP receptor D) hydrolysis of GTP by the translocator E) synthesis of the protein E) synthesis of the protein Nuclear import is driven by the hydrolysis of GTP, which is triggered by an accessory protein called Ran-GAP (GTPase-activating protein). Which is true of this process?Choose one: A) Ran-GAP is present exclusively in the nucleus. B) Ran-GTP is present in high concentrations in the cytosol. C) Nuclear receptors carry Ran-GTP from the nucleus to the cytosol. D) Ran-GDP displaces proteins from nuclear import receptors inside the nucleus. E) Nuclear import receptors have the ability to catalyze hydrolysis of GTP. C) Nuclear receptors carry Ran-GTP from the nucleus to the cytosol. What enables proteins destined for nuclear import to pass through the nuclear pore?Choose one: A) They are recognized by receptors that interact with repeated amino acid sequences in proteins lining the nuclear pore. B) Their nuclear localization signal interacts with the unstructured meshwork of proteins lining the pore. C) They promote the hydrolysis of GTP, which provides the energy needed for their transport. D) They are unfolded to allow them to snake through the meshlike network of proteins lining the nuclear pore. E) Their nuclear localization signal interacts with the cytosolic fibrils that extend from the pore. A) They are recognized by receptors that interact with repeated amino acid sequences in proteins lining the nuclear pore. Where in the cell are some proteins initially decorated with an oligosaccharide tree on asparagine residues?Choose one: A) nucleus B) Golgi apparatus C) ER D) peroxisome E) cytosol C) ER Which best describes a pathway that a protein might follow from synthesis to secretion?Choose one: A) ER → Golgi apparatus → secretory vesicle → plasma membrane B) Cytosol → ER → Golgi apparatus → transport vesicle → endosome → secretory vesicle → plasma membrane C) Cytosol → ER → secretory vesicle → plasma membrane D) ER → Golgi apparatus → transport vesicle → endosome → secretory vesicle → plasma membrane E) Cytosol → ER → transport vesicle → Golgi apparatus → transport vesicle → plasma membrane E) Cytosol → ER → transport vesicle → Golgi apparatus → transport vesicle → plasma membrane How are newly made lipids supplied to the plasma membrane?Choose one: A) via lysosomes B) via vesicles that bud from the ER and fuse with the plasma membrane C) via enzymes that synthesize phospholipids, which are attached to the plasma membrane D) via the constitutive pathway of exocytosis E) via secretory vesicles produced by the regulated exocytosis pathway D) via the constitutive pathway of exocytosis How are proteins destined to function in the ER retained there?Choose one: A) They bind to chaperones within the ER. B) They are anchored to dolichol in the ER membrane. C) They contain a C-terminal ER retention signal. D) They are embedded in the ER membrane by a transmembrane α helix. E) They retain their N-terminal ER signal sequence. C) They contain a C-terminal ER retention signal. Which of the following accurately describes a step in GTP-driven nuclear transport?Choose one: A. GTP hydrolysis powers a membrane-bound transporter protein. B. Ran-GDP escorts the nuclear receptor back to the cytosol. C. GTP-bound cargo interacts specifically with the protein fibrils of the pore. D. Binding of Ran-GTP to the receptor releases the cargo protein. D. Binding of Ran-GTP to the receptor releases the cargo protein. Where does this dehydration synthesis in the formation of a peptide bond occur? A. cytosol B. ribosome C. nucleus D. mitochondria E. stroma B. ribosome Which molecule has the most free energy? A. tRNA3 B. tRNA3 - AA3 C. AA3 - АА4 D. AA4 B. tRNA3 - AA3 All are examples of proteins that are transported into the nucleus through nuclear pores except: A. DNA and RNA polymerases B. transcription factors (TFs) C. chromatin assembly proteins (histones) D. ATP synthase E. lamins D. ATP synthase Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? A. Nuclear transport receptors would be unable to bind cargo. B. Nuclear transport receptors would be unable to enter the nucleus. C. Nuclear transport receptors would be unable to release their cargo in the nucleus. D. Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils. C. Nuclear transport receptors would be unable to release their cargo in the nucleus. Your research studies Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statement must be true A. Fuzzy has a C-terminal signal sequence that binds to SRP. B. Only one ribosome can be bound to the mRNA encoding Fuzzy during translation. C. Fuzzy must contain a hydrophobie stop-transfer sequence. D. Once the signal sequence from Fuzzy has been cleaved, the signal peptide remains in the ER membrane while Fuzzy is released. D. Once the signal sequence from Fuzzy has been cleaved, the signal peptide remains in the ER membrane while Fuzzy is released. All of the proteins below should be retained by the ER instead of being sent to the Golgi, except: A. SRP receptor B. a plasma membrane protein C. translocation channel D. signal peptidase B. a plasma membrane protein When cells respond to an extracellular signal, they most often convert the information carried by this molecule from one form to another. What is this process called?Choose one: A) signal production B) signal integration C) signal amplification D) signal transduction E) signal detection D) signal transduction When the hormone insulin is released into the bloodstream, what form of cell–cell signaling is being used?Choose one: A) endocrine B) paracrine C) neuronal D) contact-dependent A) endocrine What does a target cell require to respond to an extracellular signal molecule?Choose one or more: A) effector molecules that alter cell behavior in response to the signal molecule B) the appropriate machinery to produce and secrete the signal molecule C) access to the signal molecule D) appropriate intracellular signaling pathways E) a receptor that recognizes the signal molecule A) effector molecules that alter cell behavior in response to the signal molecule C) access to the signal molecule D) appropriate intracellular signaling pathways E) a receptor that recognizes the signal molecule Which statement about cell signaling is correct?Choose one: A) All extracellular signal molecules act by binding to receptors on the cell surface. B) Each type of extracellular signal molecule induces the same response in all target cells. C) Each receptor is generally activated by only one type of signal molecule. D) Each receptor triggers one particular type of cell behavior, for example, activating gene expression. E) All cell types are able to respond to the same set of signal molecules. C) Each receptor is generally activated by only one type of signal molecule. Which molecule performs the primary signal transduction step in cell signaling?Choose one: A) receptor protein B) scaffold protein C) extracellular signal molecule D) transcription regulator E) intracellular protein kinase A) receptor protein Which of the following statements is true?Choose one: A) Ion-channel-coupled receptors can rapidly alter the membrane potential in response to signal binding. B) Each extracellular signal molecule interacts with a single class of cell-surface receptor. C) Many ion-channel-coupled receptors have an intrinsic catalytic domain on the cytosolic side of the plasma membrane. D) G-protein-coupled receptors are GTP-binding proteins. E) All enzyme-coupled receptors have an intrinsic catalytic domain on the cytosolic side of the plasma membrane. A) Ion-channel-coupled receptors can rapidly alter the membrane potential in response to signal binding. What is true of the GTP-binding proteins that act as molecular switches inside cells?Choose one: A) They turn themselves on by hydrolyzing GTP to form GDP. B) They are active when GTP is bound. C) They are active when GDP is bound. D) They are active only in their trimeric forms. E) They turn themselves on by phosphorylating GDP to form GTP. B) They are active when GTP is bound. Which of the following statements is false?Choose one: A) Serine/threonine kinases are opposed by the action of tyrosine kinases. B) Many protein kinases are themselves activated by phosphorylation. C) Tyrosine kinases phosphorylate intracellular proteins on tyrosines. D) Serine/threonine kinases phosphorylate intracellular proteins on serines or threonines. E) Intracellular signaling pathways can include both tyrosine kinases and serine/threonine kinases. A) Serine/threonine kinases are opposed by the action of tyrosine kinases. Which type of receptors do steroid hormones generally employ?Choose one: A) enzyme-coupled receptors B) cell-surface receptors C) nuclear receptors D) G-protein-coupled receptors E) ion-channel-coupled receptors C) nuclear receptors Which is true of the GTP-binding proteins that participate in intracellular signaling?Choose one: A) Only trimeric GTP-binding proteins participate in intracellular cell signaling. B) Only trimeric GTP-binding proteins interact with guanine nucleotide exchange factors (GEFs). C) Only monomeric GTP-binding proteins relay messages from G-protein-coupled receptors. D) Only trimeric GTP-binding proteins relay messages from G-protein-coupled receptors. E) G-protein-coupled receptors interact with all types of GTP-binding proteins. D) Only trimeric GTP-binding proteins relay messages from G-protein-coupled receptors. Which statement regarding G proteins is true?Choose one: A) The GTPase activity resides in the βγ complex. B) The β subunit is tethered to the membrane by a short lipid tail. C) When a G protein is inactive, GDP is bound to its α subunit. D) Only the α subunit interacts with target proteins. E) The GTPase activity resides in the β subunit. C) When a G protein is inactive, GDP is bound to its α subunit. Signaling via a GPCR ceases when which condition occurs?Choose one: A) The α subunit exchanges GDP for GTP. B) The G protein dissociates from the activated GPCR. C) The α subunit dissociates from the βγ complex. D) The α subunit hydrolyzes its bound GTP. E) The G protein associates with an activated GPCR. D) The α subunit hydrolyzes its bound GTP. When activated phospholipase C cleaves an inositol phospholipid, what happens to the small signaling molecules the enzyme produces?Choose one: A. Both inositol 1,4,5-trisphosphate (IP3) and diacylglycerol are retained in the membrane. B. Inositol 1,4,5-trisphosphate (IP3) remains in the membrane, while diacylglycerol is released into the cytosol. C. Both inositol 1,4,5-trisphosphate (IP3) and Ca2+ are released into the cytosol. D. Both inositol 1,4,5-trisphosphate (IP3) and diacylglycerol are released into the cytosol. E. Inositol 1,4,5-trisphosphate (IP3) is released into the cytosol, while diacylglycerol is retained in the membrane. E. Inositol 1,4,5-trisphosphate (IP3) is released into the cytosol, while diacylglycerol is retained in the membrane. Which of the following is not a small intracellular signaling molecule?Choose one: A) diacylglycerol B) phospholipase C C) cyclic AMP D) inositol 1,4,5-trisphosphate E) Ca2+ B) phospholipase C What are small intracellular signaling molecules often called?Choose one: A) transmitter-gated ion channels B) second messengers C) intracellular signaling proteins D) first messengers E) extracellular signaling molecules B) second messengers When activated by a GPCR, what does adenylyl cyclase do?Choose one: A) converts cAMP to AMP B) binds to protein kinase A C) inhibits cyclic AMP phosphodiesterase D) converts AMP to cAMP E) converts ATP to cAMP E) converts ATP to cAMP Which of the following represents the correct order of signaling events that might be triggered by a GPCR that activates expression of a target gene via the production of cyclic AMP?Choose one: A) G protein → adenylyl cyclase → cyclic AMP → PKA → transcription regulator B) G protein → PKA → cyclic AMP → adenylyl cyclase → transcription regulator C) G protein → adenylyl cyclase → cyclic AMP → PKC → transcription regulator D) adenylyl cyclase → cyclic AMP → G protein → PKA → transcription regulator E) G protein → cyclic AMP → adenylyl cyclase → PKA → transcription regulator A) G protein → adenylyl cyclase → cyclic AMP → PKA → transcription regulator How can cyclic AMP, generated by adenylyl cyclase at the plasma membrane, activate the transcription of target genes?Choose one: A) The cyclic AMP binds to and activates cytosolic nuclear receptors, which enter the nucleus to transcribe target genes. B) The cyclic AMP binds to and activates specific transcription regulators. C) The cyclic AMP diffuses into the nucleus and binds to a cyclic AMP response element on target genes. D) The cyclic AMP opens channels in the nuclear membrane, allowing transcription regulators to enter and activate genes. E) The cyclic AMP activates PKA, which can enter the nucleus and phosphorylate specific transcription regulators. E) The cyclic AMP activates PKA, which can enter the nucleus and phosphorylate specific transcription regulators. When activated by the binding of Ca2+, calmodulin relays the Ca2+ signal onward by doing what action?Choose one: A) binding to cyclic AMP B) transferring its bound Ca2+ to various intracellular proteins, thereby activating them C) binding to Ca2+/calmodulin-dependent protein kinases D) destroying its bound Ca2+ E) binding to various extracellular proteins and directly activating them C) binding to Ca2+/calmodulin-dependent protein kinases Which of the following steps are required in the activation of the G-protein signaling pathway?Choose one or more: A.The activated receptor induces interaction between Gα and Gβγ. B.Ligand binds to the G-protein-coupled receptor. C.Gα exchanges GDP for GTP. D.Activated Gα influences target proteins. B.Ligand binds to the G-protein-coupled receptor. C.Gα exchanges GDP for GTP. D.Activated Gα influences target proteins. Which of the following alterations to the signaling pathway would lead to increased transcription by the CREB protein?Choose one or more: A.inhibition of GTP hydrolysis B.inhibition of entry of PKA into the nucleus C.inhibition of cAMP breakdown D.inhibition of adenylyl cyclase A.inhibition of GTP hydrolysis C.inhibition of cAMP breakdown Which of the following would increase phosphorylation of CREB by PKA?Choose one: A. blocking ATP binding to the active site of PKA B. blocking nuclear entry of PKA C. blocking cAMP binding to the regulatory subunits of PKA D. blocking binding of the regulatory subunits to the catalytic subunits of PKA D. blocking binding of the regulatory subunits to the catalytic subunits of PKA What is required for PKC activation?Choose one: A. binding to Gq and DAG B. binding to Gq C. binding to DAG D. continuing presence of Ca2+ E. binding to DAG and continuing presence of Ca2+ E. binding to DAG and continuing presence of Ca2+ IP3 signaling helps regulate sweating, which is important for regulating body temperature. Anhidrosis, the inability to sweat normally, can be caused by genetic and environmental factors. A rare mutation has been identified in a family with several children suffering from anhidrosis. The mutation inactivates the protein that IP3 binds on the ER membrane. Suppose cells were isolated from affected family members and exposed to different treatments. Which of the following treatments would be able to repair the signaling defect in cells isolated from these patients? Choose one: A. activation of phospholipase Cβ in the cell B. addition of high amounts of IP3 in the cell C. addition of high amounts of Ca2+ in the cytosol D. addition of PKC to the cell C. addition of high amounts of Ca2+ in the cytosol Following the binding of an extracellular signal molecule, receptor tyrosine kinases (RTKs) do which of the following?Choose one: A) rearrange their multiple membrane-spanning helices in a way that enables self-phosphorylation B) activate (or inactivate) the α and βγ subunits of G proteins C) form dimers in which each polypeptide chain phosphorylates its own cytoplasmic tail D) form dimers in which each polypeptide chain cross-phosphorylates the cytoplasmic tail of its partner. E) become internalized so that they can phosphorylate and activate various intracellular signaling proteins D) form dimers in which each polypeptide chain cross-phosphorylates the cytoplasmic tail of its partner What do the phosphorylated tyrosines on activated RTKs do?Choose one: A) They help the receptor dimerize. B) They promote receptor internalization. C) They serve as binding sites for a variety of intracellular signaling proteins. D) They activate the enzymatic activity of the RTKs. E) They serve as binding sites for G proteins. C) They serve as binding sites for a variety of intracellular signaling proteins. Ras is activated by a Ras-activating protein that does what?Choose one: A) causes Ras to interact with a phosphorylated RTK B) causes Ras to exchange GDP for GTP C) causes Ras to hydrolyze its bound GTP D) phosphorylates Ras E) dephosphorylates Ras B) causes Ras to exchange GDP for GTP Certain mutant Ras proteins cannot hydrolyze their bound GTP to GDP, and therefore cannot do which of the following?Choose one: A) activate MAP kinase directly B) promote cell proliferation C) be degraded D) turn themselves off E) turn themselves on D) turn themselves off PI 3-kinase acts by phosphorylating what molecule(s)?Choose one: A) tyrosines on protein kinases that phosphorylate Akt B) serines or threonines of Akt C) tyrosines of Akt D) serines or threonines on protein kinases that phosphorylate Akt E) inositol phospholipids E) inositol phospholipids The signaling pathways shown below integrate information provided by signal 1 and signal 2 to activate the transcription of a target gene and trigger a cell response. The intracellular signaling molecules in the pathway are only active when they receive an activating signal (→) from an upstream signaling molecule and are not being inhibited (—I) by any upstream signaling molecule.Given this information, under what conditions will the target gene for this signaling network be expressed?Choose one: A. The target gene will be expressed only when both signals are present. B. The target gene will be expressed only when both signals are absent. C. The target gene will be expressed only when signal 2 is present. D. The target gene will be expressed when either signal is present on its own. E. The target gene will be expressed only when signal 1 is present. Ras can exist in two different conformations or states, inactive and active. Which of the following correctly describe(s) the stably active state of Ras?Choose one or more: A.Ras is bound to GTP. B.Switch 1 and switch 2 regions are in an active conformation. C.Ras is bound to Ras-GAP. D.Ras is bound to GDP. A.Ras is bound to GTP. B.Switch 1 and switch 2 regions are in an active conformation. Specific amino acids, including Arg 789 in Ras-GAP and amino acids Gln 61 and Thr 35 in Ras, all play an important role in Ras function. Why are these amino acids important? Choose one: A. They help downstream signaling by binding to additional signaling proteins. B. They help facilitate GTP hydrolysis by Ras. C. They help Ras bind GTP tightly. D. They help Ras bind GDP tightly. B. They help facilitate GTP hydrolysis by Ras. Which is true of the Notch signaling pathway?Choose one: A) The Notch receptor is activated by cyclic AMP. B) The Notch receptor is located in the nuclear membrane. C) The tail of the cell-surface receptor travels to the nucleus where it regulates gene transcription. D) The Notch receptor activates gene expression by triggering the production of cyclic AMP. E) Notch is an intracellular receptor that travels to the nucleus where it regulates gene transcription. C) The tail of the cell-surface receptor travels to the nucleus where it regulates gene transcription. Which statement about secretion is true? A. The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior. B. Vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received from the cell. C. The signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles. D. Proteins destined for constitutive exocytosis accumulate in the trans Golgi network until a signal is received. A. The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior. Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following 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 a minute of receiving the signal. 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. How would you order the different types of cell signaling from the type in which the signal molecule travels the shortest distance to the type in which the signal molecule travels the greatest distance. A. cell-cell, synaptic, paracrine, endocrine B. cell-cell, paracrine, endocrine, synaptic C. cell-cell, endocrine, paracrine, synaptic D. paracrine, cell-cell, synaptic, endocrine A. cell-cell, synaptic, paracrine, endocrine Which is not a cell-surface receptor? A. neurotransmitter-gated ion channel B. Enzymatic receptor C. GPCR D. G protein D. G protein Which statement below is false? A. Neurotransmitters are small molecules released into the synaptic cleft after the fusion of synaptic vesicles with the pre-synaptic membrane. B. Action potentials are usually mediated by voltage-gated Ca?* channels. C. Voltage-gated Na* channels become automatically inactivated shortly after opening, which ensures that the action potential cannot move backward along the axon. D. The binding of a neurotransmitter to its receptor on the post-synaptic cell changes the membrane potential of that cell. B. Action potentials are usually mediated by voltage-gated Ca?* channels How is the action of dopamine regulated in response to excessive stimulation due to the presence of cocaine? A. enzymatic degradation of neurotransmitter B. re-uptake by the pre-synaptic membrane C. modulation of the post-synaptic receptors D. balance between excitatory and inhibitory neurotransmitters C. modulation of the post-synaptic receptors Photosynthesis is a process that takes place in chloroplasts and uses light energy to generate high energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chain located in chloroplasts? thylakoid membrane Stage 2 of photosynthesis, sometimes referred to as the dark reactions, involves the reduction of CO2 to produce organic compounds such as sucrose. What cofactor is the electron donor for carbon fixation? NADPH The photosystems in chloroplasts contain hundreds of chlorophyll molecules, most of which are part of the antenna complex. In the electron-transport chain in chloroplasts, __________-energy electrons are taken from __________. low; H2O In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast? thylakoid space What is the role of the nuclear localization signal in a nuclear protein? A) It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. B) It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. C) It aids in protein unfolding so that the protein can thread through nuclear pores. D) It prevents the protein from diffusing out of the nucleus through nuclear pores. It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. Your friend works for a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? A. Nuclear transport receptors would be unable to bind cargo. B. Nuclear transport receptors would be unable to enter the nucleus. C. Nuclear transport receptors would be unable to release their cargo in the nucleus. D. Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils. C. Nuclear transport receptors would be unable to release their cargo in the nucleus. Which of the following choices reflects the appropriate order of locations through which a newly synthesized protein destined for the plasma membrane travels? ER → Golgi → plasma membrane Which of the following statements about disulfide bond formation is FALSE? Disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing. Vesicles from the ER enter the Golgi at the cis Golgi network. Which of the following is false regarding the similarities and differences between endocrine and paracrine signaling? A. Paracrine signals remain in localized areas while endocrine signals move throughout the body B. Both secreted signals (typically) don't trigger responses in the cell that the signal was originally sent from C. Both signals sent through secreted molecules reach their target receptors by diffusion D. The signals from the endocrine system are low in concentration while those from the paracrine system are high in concentration C. Both signals sent through secreted molecules reach their target receptors by diffusion Q1. ATP synthesis in the thylakoid membrane is driven by: A. H+ ions flowing against a concentration gradient B. Electrons flowing down a concentration gradient C. H+ ions flowing down a concentration gradient D. Electrons flowing against a concentration gradient E. A & B C. H+ ions flowing down a concentration gradient Q2. What is the final electron acceptor in photosyntliesis? A. 02 B. NADP+ C. NAD+ D. FADH2 В. CO2 C. NAD+ What is the ultimate electron donor in photosynthesis? H2O Which of the following is the correct flow of electrons in photosynthesis? A. photosystem I → cytochrome b6-f complex → photosystem II B. photosystem 1 → photosystem II → ATP synthase C. photosystem II → cytochrome b6-f complex → photosystem I D. photosystem II → ATP synthase → thylakoid space E. water → electron transport chain → thylakoid space C. photosystem II → cytochrome b6-f complex → photosystem I Which is NOT a step in the nuclear translocation cycle? A. Nuclear transport receptor importin binds the NLS of the cargo protein B. Ran-GDP binds importin inside the nucleus, causing release of the cargo C. RanGAP removes a P, from GTP D. Ran-GTP is hydrolyzed to Ran-GDP in the cytoplasm E. Importin release is coupled to GP hydrolysis outside the nucleus B. Ran-GDP binds importin inside the nucleus, causing release of the cargo Which of the following Transcription factors are required for immune response? A. NF-Kappa B B. Pho4 C. Ran-GTP D. Ran-GAF E. B&D A. NF-Kappa B Which statement is correct? A. An NLS is located at the beginning of the polypeptide. B. An NLS is typically negatively charged. C. Active transport of RNA into the nucleus requires an NLS D. An NLS is exported out of the nucleus into the cytosol. E. An NLS is part of the Importin that binds to cargo protein. B. An NLS is typically negatively charged. Identify the mismatched pair: A. Dopamine - EPSP B. GABA - IPSP C. Serotonin - EPSP or IPSP D. Glutamate - IPSP E. A & C D. Glutamate - IPSP The inflow of which on causes neurotransmitter-containing synaptic vesicles to fuse to the axon membrane? A. Nat B. K+ C. Cu2+ D. Ca2+ E. A & C D. Ca2+ If a mutation occurs in the purine salvage pathway resulting in Hypoxanthine phosphoribosyltransferase (HPRT) not being made, what can be said about a person suffering from this condition? A. A diet rich in protein can benefit this condition B. In the absence of HPRT the intermediate Hypoxanthine is not converted to Uric acid but is converted to Inosinate which is responsible for the swelling of joints and crystal accumulation C. In the absence of HPRT the intermediate Hypoxanthine is not converted to inosinate but converted to Uric acid D. This disorder is not inherited, the improper enzyme function is accumulated by a diet rich in protein and fats. This is why gout was known as the deli man's disease C. In the absence of HPRT the intermediate Hypoxanthine is not converted to inosinate but converted to Uric acid Which is false of Ran (a GP-binding protein) in the translocation cycle? A. Ran-GTP binds to the nuclear transport receptor and retains the cargo without dissociation B. Ran-GTP binds to the nuclear transport receptor and will cause dissociation, leading to the cargo protein being released in the nucleus C. Once the nuclear transport receptor dissociates from Ran-GDP, it's freely available to bind to more cargo D. Ran-GDP in the cytoplasm occurs after Ran-GAP induces Ran to hydrolyze its bound GTP A. Ran-GTP binds to the nuclear transport receptor and retains the cargo without dissociation What is a SRP and what is its function during synthesis of secreted proteins? A. Secretion recognition particle; catalyzes the phosphorylation of proteins on its way to the E.R. B. Signal recognition particle, removes the signal sequence from newly synthesized proteins C. Signal recognition particle; docks on the SRP receptor on the E.R. membrane, helping with translocation D. Secretion recognition particle; modifies carbohydrates on proteins as they are synthesized C. Signal recognition particle; docks on the SRP receptor on the E.R. membrane, helping with translocation What happens when a cell-surface receptor activates a G protein? A. The ß subunit exchanges its bound GDP for GTP. B. The GDP bound to the a subunit is phosphorylated to form bound GTP. C. The a subunit exchanges its bound GDP for GTP. D. It activates the a subunit and inactivates the By complex. C. The a subunit exchanges its bound GDP for GTP. When acetylcholine binds to a GPCR on heart muscle, the activated receptor stimulates a G protein, which opens a K* channel in the plasma membrane. Which of the following would enhance this effect of the acetylcholine? A. addition of a high concentration of a non-hydrolyzable analog of GTP B. addition of a drug that prevents the a subunit from exchanging GDP for GTP C. mutations in the acetylcholine receptor that weaken the interaction between the receptor and acetylcholine D. mutations in the acetylcholine receptor that weaken the interaction between the receptor and the G protein A. addition of a high concentration of a non-hydrolyzable analog of GTP Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase. Consider skeletal muscle cells which have a constitutively active mutant form of PKA (= remains constantly ON). Which of the following is false? A. This would lead to a decrease in the amount of unphosphorylated phosphorylase kinase. B. This would not increase the affinity of adrenaline for the receptor. C. This would lead to an excess in the amount of glucose available. D. This would lead to an excess in the amount of glycogen available. D. This would lead to an excess in the amount of glycogen available. Q4. Which alteration would reduce the amount of Ca?+ released from the ER to the cytosol? A. an altered PIP2 that cannot be hydrolyzed B. a mutant By G protein complex C. an altered DAG D. a mutant CaM kinase A. an altered PIP2 that cannot be hydrolyzed The growth factor RGF stimulates proliferation of cultured rat cells. It is bound by a receptor tyrosine kinase called RGFR. Which of the following types of alteration to RGFR 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 alanine B. a mutation that prevents RGFR from binding to RGF The length of time that a G protein will signal is determined by the GTPase activity of Gα. Your lab has discovered an unidentified extracellular signal molecule called QGF. add purified QGF to different cells to determine its effect on these cells. add QGF to heart muscle cells, you observe an increase in cell contraction. you add it to fibroblasts, they undergo cell division. you add it to nerve cells, they die. you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be true? A) Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells. B) Glial cells do not have a receptor for QGF. C) QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. D) Heart muscle cells, fibroblasts, and nerve cells must all have the same receptor for QGF. C) QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. What happens when a G-protein-coupled receptor (GPCR) 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. C) The α subunit exchanges its bound GDP for GTP. 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. contact-dependent 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. A) Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. 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(s) 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 cellular response. D) Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response 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. Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in Figure 16-7. Which of the following statements is FALSE? A) In the presence of a survival signal, Akt is phosphorylated. B) In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2. C) In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active. D) In the absence of a survival signal, Bad is phosphorylated. D) In the absence of a survival signal, Bad is phosphorylated. Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that break