Cell bio final
What are the several lines of evidence that suggest Apg7 is a ubiquitin- E1-like enzyme in the Apg5/Apg12 conjugation system?
"As shown in Fig. 2, the apg7 and apg10 mutants failed to conjugate Apg5 and Apg12, suggesting that these two APG products may function as an enzyme system for conjugation. Cloning of the APG7 gene revealed that it encodes a 630-amino-acid protein with predicted Mr of 71.4K (Fig. 5a). The region containing amino acids 322-392 of Apg7 shows significant homology with the corresponding region in E1, the ubiquitin-activating enzyme in S. cerevisiae. and in other species (data not shown). This region encompasses a putative ATP-binding site (GxGxxG)17, suggesting that Apg7 may be an Apg12-activating enzyme. Although the sequence around the active-site cysteine is less conserved, alignments between Apg7 and other E1-like enzymes indicate that Cys 507 is a putative active-site cysteine." "Apg12 is activated by binding to Apg7 via a high-energy thioester bond; through transfer to an E2-like molecule (possibly Apg10), Apg12 is finally conjugated to Lys 149 of Apg5 via an isopeptide bond. Although the steps in this conjugation pathway are similar to those that occur in ubiquitination14-16 and in the modification by other ubiquitin-like proteins." Figure 5 shows DNA sequence similarity between Apg7 and E1 protein ATP binding site in Apg7 showing the process requires ATP Apg7 mutants (nonfunctional Apg7) failed to conjugate
transmission electron microscope
A microscope that uses an electron beam to study the internal structure of thinly sectioned specimens.
scanning electron microscope
An electron microscope used to study the fine details of cell surfaces
What is the main idea of the autophagy paper?
Apg12 is conjugated to Apg5 by binding to other Apg molecules (such as Apg7 and Apg10) apg 12 acts as a ubiquitin-like protein and apg 7 acts as a E1 enzyme to conjugate.
What's the physiological significance of autoinhibition of UNC-104/KIF1A (i.e. How synaptogenesis is affected when the autoinhibition of UNC-104/KIF1A is disrupted)?
Autoinhibition of UNC-104 and ARL-8 determine synaptic localization, and synapse diversity is reduced in mutants. This is due to increased movement and reduced pauses, which can cause better separation of en passant synapses during synaptogenesis.
What is the main message of the unc-104 paper?
Excessive activation of UNC-104 causes synaptic vesicles to not be transported across the synapse, which leads to a build up of SVs on the pre-synaptic side. This causes the worm to become paralyzed
In the paper they used two methods to label nucleus (DAPI or His2B-GFP) and microtubules (immunostaining with anti-tubulin antibody or tubulin-GFP) respectively. In which experiments did they use those different methods and why?
His2B-GFP was used to label chromosomes in order to visualize their localization patterns when Sept2 was knocked down. This method was used because the researchers wanted to focus specifically on chromosomal localization without seeing the interference of microtubules. Tubulin-GFP was used when cells were fixed and stained in order to visualize the comparison between Sept2 and microtubule localization. This showed that mitotic spindles required Sept2 in order to properly align chromosomes at the metaphase plate. His2B-GFP is a GFP marker on the histone 2B protein, which is localized to the chromosomes. This was used to visualize chromosomes when cells were not fixed to observe them in live-imaging long term. DAPI can only be used on fixed cells. Similarly, tubulin-GFP can be used to observe live cells over a long period of time, but immunostaining with anti-tubulin requires using a fixed cell. When cells are dead (fixed) they become static, and changes cannot be observed.
Describe the localization of wild-type UNC-104 and UNC-104(E612K) in DA9 neuron. In figure3C, what is DsRed used for?
In the wild-type, the UNC-104::GFP was detected in the cell body and axon, and somewhat in the synaptic region and distal axonal tip. In the mutant, there was localization of the GFP signal at the axonal tip, and none in the cell body. The DsRed is used to show the cell body in the mutant where the GFP is undetectable.
fluorescence microscope
Instrument used to visualize a specimen that has been labeled with a fluorescent dye; samples are illuminated with a wavelength of light that excites the dye, causing it to fluoresce.
Through which experiments, did they conclude that the carboxy-terminal glycine residue of Apg12, is conjugated to a lysine at residue 149 of Apg5?
It was determined through the third and fourth set of experiments. Replacing lysine with arginine in apg5
What is the difference between knockout and knockdown? Why did they choose to knock down septins in the paper?
Knocked out genes are permanently altered or deleted which results in a complete loss of function of that gene. This is usually effective at the DNA level. Has potential pleiotropic effects (disadvantage). Knocked down genes are temporarily inactivated which results in a reduction in the expression of that gene. It is effective at the RNA level. Leftover protein could still have some function (disadvantage). They chose to knock down septins in order to not entirely deplete the septin network, making the cell entirely dysfunctional. Without septin, cells would be unable to form mitotic spindles, and the researchers would not be able see the functions of septin in chromosomal congression and segregation as clearly. Otherwise, mitosis wouldn't occur at all and could even cause cell death.
What is nocodazole? In what experiments did they treat cells with nocodazole and what did they conclude?
Nocodazole is a drug used to deplete microtubules. It works by interfering with MT ability to depolymerize by binding to beta-tubulin. It was used during the RNA interference experiment to knockdown Sept2 in order to compare to the control. When Sept2 was silenced and nocodazole was added, the septin network was not detected but spindle length and bipolarity was unaffected. Septin is reduced after treated by nocodazole but not gone. Sept2 localizes to mitotic spindle and to metaphase plate independent of the microtubules. Septins are required for CENP-E localization at kinetochores in the absence of microtubules. Using mock as control by treating with transfection agent but not siRNA. With nocodazole treatment CENP-E still localizes to kinetochore in the absence of MT. When septin was knocked down then CENP-E were unable to localize to the kinetochores. This suggests that septin is the scaffold that supports CENP-E at the kinetochore.
What is phenylmethylsulphonyl fluoride (PMSF)? Where (in which experiment) and why did they add PMSF to yeast cells?
PSMF is serine protease inhibitor commonly used in the preparation of cell lysates. They were added to the cells as part of a nitrogen-starvation medium before they were incubated in the first experiment.
Where is Sept 2 localized in a dividing cell?
Sept2 is localized to the midbody, cleavage furrow, and the central spindle. Metaphase - mitotic (central) spindle Anaphase-telophase-cytokinesis - midbody and cleavage furrow
What is the main idea of the mitosis paper?
The GTP-binding protein septins serve as a scaffold to maintain proteins (such as CENP-E) at the metaphase plate. This scaffolding system provides a potential mechanism for the coordination of cytokinesis with chromosome congression & segregation
In the electron microscope micrograph of nutrient-starved mouse embryonic fibroblasts, The arrows indicate: a) Autophagosomes b) Lysosomes c)Mitochondria d) Autolysosomes
a) Autophagosomes
Which of the following statements about vesicle budding from the Golgi is FALSE? a) Clathrin molecules are important for binding to and selecting cargoes for transport. b) Adaptins interact with clathrin. c) Once vesicle budding occurs, clathrin molecules are released from the vesicle. d) Clathrin molecules act at the cytosolic surface of the Golgi membrane.
a) Clathrin molecules are important for binding to and selecting cargoes for transport. (FEEDBACK: Cargo binds to cargo receptors. Adaptin molecules capture cargo receptors, which bind to the appropriate cargo molecules for incorporation into the vesicle.)
The following immunofluorescence images showed two sets of mouse embryonic fibroblasts (MEF) stained by antibodies against ATG9A or GM130 (a Golgi protein). DAPI staining (blue) was used to visualize the nuclear. Scale bar=10um. What do these images tell you? a) The adaptor AP-4 sorts the protein ATG9A from Golgi to peripheral compartments b) The autophagy protein ATG9A sorts the adaptor AP-4 from Golgi to peripheral compartments c) The adaptor AP-4 sorts the Golgi protein GM130 to peripheral compartments d) The Golgi protein GM130 sorts the adaptor AP-4 from Golgi to peripheral compartments
a) The adaptor AP-4 sorts the protein ATG9A from Golgi to peripheral compartments
In Figure 5C. Lysates of Δapg5 cells and Δapg12 cells were mixed in vitro and incubated with or without ATP. Figure 5c shows that the 70K band appeared in a time- dependent and ATP-dependent manner. Why didn't they use lysates from wild-type cells for this experiment?
Wild types would have free ATP that could not be controlled like figure 5c Wild-types wouldn't have knockout genes and wouldn't know if conjugation takes place with or without ATP because they would already have conjugate
When cells are starved, autophagy is initiated by a) The inhibition of mTOR signaling pathway b) The activation of mTOR signaling pathway c) The inhibition of Notch signaling pathway d) The activation of Notch signaling pathway
a) The inhibition of mTOR signaling pathway
The following immunofluorescence images showed wild-type (WT) mouse embryonic fibroblasts (MEFs) incubated for 0 or 60 min in amino acid- and serum-free DMEM (starvation). The cells were stained by antibodies against LC3B (an autophagosome-associated protein). DAPI staining (blue) was used to visualize the nuclear. (Scale bar=10um). Which of the following statements is FALSE? a) Upon starvation, the cells moved closer to each other b) Upon starvation, autophagy was induced to provide the cells with nutrients c) Upon starvation, the number of autophagosomes was increased d) Upon starvation, the cells did not move closer to each other
a) Upon starvation, the cells moved closer to each other
A ubiquitin is a) a polypeptide that can be attached to another peptide or protein b) a lipid molecule that can be conjugated to a peptide or protein c) a sugar molecule that can be attached to a peptide or protein d) a lipid molecule that can form non-covalent bonds with a peptide or protein
a) a polypeptide that can be attached to another peptide or protein
The region of a chromosome to which the microtubules of the mitotic spindle attach, via the kinetochore, during cell division is called__________. a) centromere b) centrosome c) chromatid d) cohesin
a) centromere
The principle microtubule-organizing center in animal cells is the a) centrosome b) centromere c) kinetochore d) cell cortex
a) centrosome
Proteins that are fully translated in the cytosol and lack a sorting signal will end up in the a) cytosol. b) mitochondria. c) interior of the nucleus. d) nuclear membrane.
a) cytosol (FEEDBACK: Proteins produced in the cytosol that lack sorting signals remain in the cytosol. Proteins produced in the cytosol and destined for the mitochondria or the interior of the nucleus will have a sorting signal to direct the protein to its proper location. Proteins destined for the nuclear membrane are not translated in the cytosol.)
Which of the following does not occur during M phase in animal cells? a) growth of the cell b) condensation of chromosomes c) breakdown of nuclear envelope d) attachment of chromosomes to microtubules
a) growth of the cell
Sister chromatid separation occurs because __________ are destroyed by the APC/C. a) securins b) cohesins c) kinetochores d) condensins
a) securins
Most lysosomal enzymes are acid hydrolases, which are active at pH of 5. The acidic environment inside the lysosome is maintained by a proton pump called a) v-ATPase (vacuolar-ATPase) b) NMDA receptor c) IP3 receptor d) The complex I proton pump
a) v-ATPase (vacuolar-ATPase)
The proteasome is a) A membrane bound organelle that degrades target proteins b) A protein complex of over 50 subunits that degrades target proteins c) An hydrolytic enzyme inside the lysosome that degrades target proteins d) A protein complex composed of three subunits that degrades target proteins
b) A protein complex of over 50 subunits that degrades target proteins
The main steps of autophagy are: a) Autophagy initiation -> Membrane nucleation and autophagosome formation -> autophagosome expansion and phagophore formation -> Fusion with the lysosome and degradation b) Autophagy initiation -> Membrane nucleation and phagophore formation -> Phagophore expansion and autophagosome formation -> Fusion with the lysosome and degradation c) Autophagy initiation -> Membrane nucleation and autophagosome formation -> autophagosome expansion and phagophore formation -> Fusion with the lysosome and degradation -> mTOR signaling activation d) Autophagy initiation -> Membrane nucleation and phagophore formation -> Phagophore expansion and autophagosome formation -> Fusion with the lysosome and degradation -> mTOR signaling activation
b) Autophagy initiation -> Membrane nucleation and phagophore formation -> Phagophore expansion and autophagosome formation -> Fusion with the lysosome and degradation
Cholesterol derived from low-density lipoprotein (LDL) is taken into cells through endocytosis mediated by LDL receptors (LDLRs). Which of the following is FALSE: a) LDL receptors dissociate with LDL inside endosomes and are recycled back to the plasma membrane b) LDL receptors dissociate with LDL inside lysosomes and are recycled back to the plasma membrane c) LDL is degraded inside lysosomes and releases free cholesterol for membrane synthesis d) Too much LDL cholesterol can contribute to the formation of plaque buildup in the arteries
b) LDL receptors dissociate with LDL inside lysosomes and are recycled back to the plasma membrane
Which of the following statements about the endoplasmic reticulum (ER) is FALSE? a) The ER is the major site for new membrane synthesis in the cell. b) Proteins to be delivered to the ER lumen are synthesized on the smooth ER. c) Steroid hormones are synthesized on the smooth ER. d) The ER membrane is contiguous with the outer nuclear membrane.
b) Proteins to be delivered to the ER lumen are synthesized on the smooth ER. (FEEDBACK: Proteins to be delivered to the ER lumen are synthesized on rough ER; these areas appear "rough" because ribosomes are attached to the cytosolic surface of these ER regions.)
The TrkB receptor is located on the plasma membrane of neurons. It binds to the neurotrophic factor BDNF and plays an important role in neuronal survival and growth. Once bound with BDNF, TrkB is endocytosed and undergoes degradation. Internalized TrkB is most likely to be degraded via: a) The ubiquitin-proteasome pathway b) The endo-lysosomal pathway c) Autophagy d) None of the above
b) The endo-lysosomal pathway
Which of the following events does NOT usually occur during interphase? a) Cells grow in size. b) The nuclear envelope breaks down. c) DNA is replicated. d) The centrosomes are duplicated.
b) The nuclear envelope breaks down.
Which of the following is likely to be degraded by the ubiquitin-proteasome pathway a) Aged and dysfunctional mitochondria b) Transcriptional factors c) Oxidized lipids d) All of the above
b) Transcriptional factors
Molecules to be packaged into vesicles for transport are selected by a) clathrin. b) adaptins. c) dynamin. d) SNAREs.
b) adaptins
The process of synaptic vesicle fusion with the presynaptic membrane and release of neurotransmitters is a type of a) Endocytosis b) Exocytosis c) Cell division d) Protein degradation
b) exocytosis
Progression through the cell cycle requires a cyclin to bind to a Cdk because a) the cyclins are the molecules with the enzymatic activity in the complex. b) the binding of a cyclin to Cdk is required for Cdk enzymatic activity. c) cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle. d) without cyclin binding, a cell-cycle checkpoint will be activated.
b) the binding of a cyclin to Cdk is required for Cdk enzymatic activity.
Why is unc-104 (wy873[E612K]) a gain-of-function mutation?
because it disrupts the autoinhibition of the kinesin and enables the mutant kinesin to bind to MTs and SVs
Botulinum neurotoxins (BoNTs) and tetanus neurotoxins (TeNT) are the most potent toxins known and cause botulism and tetanus, respectively, by a) Causing DNA double-strand breaks b) Degrading neurotransmitters c) Cleaving SNAREs and preventing synaptic vesicle fusion d) All of above
c) Cleaving SNAREs and preventing synaptic vesicle fusion
The anaphase-promoting complex or cyclosome (APC/C) is a) E1 ubiquitin-activating enzyme b) E2 ubiquitin-conjugating enzyme c) E3 ubiquitin ligase d) Deubiquitinase
c) E3 ubiquitin ligase
Which of the following statements about the anaphase-promoting complex (APC) is FALSE? a) It promotes the degradation of proteins that regulate M phase. b) It inhibits M-Cdk activity. c) It is continuously active throughout the cell cycle. d) M-Cdk stimulates its activity.
c) It is continuously active throughout the cell cycle. (only active during anaphase)
Which of the following statements about the movement of materials in a nerve axon is TRUE? a) Movement along microtubules in the axon is slower than free diffusion, but necessary due to the importance of directional transport. b) The small jerky steps seen when vesicles move along microtubules are due to the shrinkage of microtubules that occurs when axonal microtubules undergo dynamic instability. c) Microtubules within an axon are arranged such that all microtubules point in the same direction with their minus ends toward the nerve cell body. d) Microtubules within the axon support the unidirectional motion of materials from the nerve cell body to the axon terminal, while materials transported back from the axon terminal to the cell body move along intermediate filaments.
c) Microtubules within an axon are arranged such that all microtubules point in the same direction with their minus ends toward the nerve cell body. (FEEDBACK: Movement along microtubules is faster than free diffusion. The microtubules within the axon are typically stabilized and not undergoing dynamic instability. The saltatory movement of the cargo is due to the properties of the motor proteins that transport the cargo along microtubule tracks. Movement in axons is bidirectional.)
Which of the following confers specificity to the ubiquitin-proteasome pathway a) The E1 ubiquitin-activating enzymes because they specifically activates ubiquitin b) The E2 ubiquitin-conjugating enzymes because they specifically conjugates ubiquitin to target proteins c) The E3 ubiquitin ligases because they recognize protein substrates, and facilitate the transfer of ubiquitin from the E2 to the protein substrates. d) The E2 ubiquitin-conjugating enzymes because they recognize protein substrates, and facilitate the transfer of ubiquitin from the E3 to the protein substrates.
c) The E3 ubiquitin ligases because they recognize protein substrates, and facilitate the transfer of ubiquitin from the E2 to the protein substrates.
Which of the following statements about vesicular membrane fusion is FALSE? a) Membrane fusion does not always immediately follow vesicle docking. b) The hydrophilic surfaces of membranes have water molecules associated with them that must be displaced before vesicle fusion can occur. c) The GTP hydrolysis of the Rab proteins provides the energy for membrane fusion. d) The interactions of the v-SNAREs and the t-SNAREs pull the vesicle membrane and the target organelle membrane together so that their lipids can intermix.
c) The GTP hydrolysis of the Rab proteins provides the energy for membrane fusion. (FEEDBACK: Rab proteins are important for docking, but are not involved in the catalysis of membrane fusion.)
Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2? a) The cell would be unable to enter M phase. b) The cell would be unable to enter G2. c) The cell would enter M phase under conditions when normal cells would not. d) The cell would pass through M phase more slowly than normal cells.
c) The cell would enter M phase under conditions when normal cells would not.
Which of the following about autophagy is FALSE: a) The hallmark of autophagy is the double-membrane structure called autophagosome b) Since SNARE proteins are essential for the fusion of lipid bilayers, these proteins are required for autophagosome-lysosome fusion c) The inner membrane of autophagosomes fuses lysosomes and form autolysosomes, which degrade the content inside the autophagosomes d) The outer membrane of autophagosomes fuses lysosomes and form autolysosomes, which degrade the content inside the autophagosomes
c) The inner membrane of autophagosomes fuses lysosomes and form autolysosomes, which degrade the content inside the autophagosomes
Cohesins are cleaved by separases at__________. a) metaphase b) prophase c) anaphase d) prometaphase
c) anaphase
The clearance of damaged cellular organelles, including mitochondria, is done by: a) The ubiquitin-proteasome pathway b) The endo-lysosomal pathway c) Autophagy d) All of the above
c) autophagy
Vesicles from the ER enter the Golgi at the a) medial cisternae. b) trans Golgi network. c) cis Golgi network. d) trans cisternae.
c) cis Golgi network
At the end of DNA replication, the sister chromatids are held together by the a) kinetochores. b) securins. c) cohesins. d) histones.
c) cohesins.
Signal sequences that direct proteins to the correct compartment are a) added to proteins through post-translational modification. b) added to a protein by a protein translocator. c) encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination. d) always removed once a protein is at the correct destination
c) encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination. (FEEDBACK: Signal sequences are found within the amino acid sequence of proteins. They are sometimes removed when the protein is at the correct destination, but not all are removed. For example, nuclear import signals are not removed once a protein is inside the nucleus. A protein translocator resides in the membrane and helps transport soluble proteins across the membrane, but does not add signal sequences to proteins.)
Which of the following organelles is not part of the endomembrane system? a) Golgi apparatus b) the endosome c) mitochondria d) lysosomes
c) mitochondria (FEEDBACK: Mitochondria are not part of the endomembrane system, which is thought to have arisen initially through invagination of the plasma membrane. Instead, mitochondria (and chloroplasts) are thought to have evolved from a bacterium that was engulfed by a primitive eukaryotic cell.)
Kinesins and dyneins a) have tails that bind to the filaments. b) move along both microtubules and actin filaments. c) often move in opposite directions to each other. d) derive their energy from GTP hydrolysis.
c) often move in opposite directions to each other (FEEDBACK: All other answers are false. The motor heads bind to the filaments. Both motors move along microtubules and use ATP hydrolysis for energy.)
Consider the in vitro motility assay using purified kinesin and purified polymerized microtubules shown in Figure 17-37. The three panels are images taken at 1-second intervals. In this figure, three microtubules have been numbered to make it easy to identify them. Which of the following statements about this assay is FALSE? Figure 17-37 [saved] a) Kinesin molecules are attached by their tails to a glass slide. b) The microtubules used in this assay must be polymerized using conditions that stabilize tubule formation or else they would undergo dynamic instability. c) ATP must be added for this assay to work. d) Addition of the nonhydrolyzable ATP analog (AMP-PNP) would cause the microtubules to move faster.
d) Addition of the nonhydrolyzable ATP analog (AMP-PNP) would cause the microtubules to move faster. (FEEDBACK: Addition of AMP-PNP would block movement, because ATP hydrolysis is required for the kinesin to step along a microtubule. The addition of AMP-PNP would cause the microtubules to attach to the kinesin heads without being released. Kinesin molecules are attached to the slide by their tails (the cargo-binding domain) so that the heads are available to move the microtubules along the slides. If they were in solution with the microtubules, there would be no force and thus no movement. The microtubules used in this assay are stabilized with a nonhydrolyzable form of GTP, because otherwise they might shrink during the course of the assay. ATP is required for kinesin movement, and thus must be added for this assay to work.)
Which of the following statements about the drugs colchicine and Taxol® is True? a) Colchicine and Taxol® are used to treat human cancers because they cause mitotic defects b) Colchicine and Taxol® disrupt the segregation of the chromosomes during mitosis c) Colchicine and Taxol® disrupt the attachments of the mitotic spindle to kinetochores. d) All of the above
d) All of the above
Which of the following statements about the spindle checkpoint is TRUE? a) The spindle checkpoint is a checkpoint at the metaphase-to-anaphase transition b) The spindle checkpoint prevents the separation of the duplicated chromosomes until each chromosome is properly attached to the spindle c) The spindle checkpoint sends a "stop" signal by the kinetochore of any unattached chromosome and inhibits APC/C d) All of the above
d) All of the above
Which of the following is NOT involved in autophagy a) autophagosome b) autolysosome c) endoplasmic reticulum (ER) d) none of the above
d) none of the above; all are involved in autophagy
The following Western blot showed the expression levels of LC3‑I and LC3‑II during starvation. Wild-type and Atg5‑/‑ mouse embryonic fibroblasts (MEFs) were cultured in DMEM without amino acids and serum for the indicated times, and then subjected to immunoblot analysis using anti‑LC3 antibody and anti‑tubulin antibody. Note that E64d and pepstatin are lysosomal inhibitors. Which of the following statements is FALSE? a) Tubulin was used as a loading control to show that the total amount of protein is the same for all lanes b) The results indicate that Atg5 is necessary for autophagosome formation c) LC3-I is the cytosolic LC3 and LC3-II is the lipidated LC3, which is conjugated to phosphatidylethanolamine (PE) of autophagosomal membranes d) Atg5 is a digestive enzyme inside lysosomes that degrades LC3-II
d) Atg5 is a digestive enzyme inside lysosomes that degrades LC3-II
Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels? a) lysosome → endosome → plasma membrane b) ER → lysosome → plasma membrane c) Golgi → lysosome → plasma membrane d) ER → Golgi → plasma membrane
d) ER → Golgi → plasma membrane
Microtubules are important for transporting cargo in nerve cell axons, as diagrammed in Figure 17-20. Notice that the two types of cargo are traveling in opposite directions. Which of the following statements is likely to be FALSE? a) The gray cargo is attached to dynein. b) The black cargo and the gray cargo require ATP hydrolysis for their motion. c) The black cargo moving toward the axon terminal contains a domain that specifically interacts with the tail domain of a particular kind of motor. d) The black cargo and the gray cargo are moving along microtubules of opposite polarity.
d) The black cargo and the gray cargo are moving along microtubules of opposite polarity. (FEEDBACK: Microtubules in nerve cell axons are generally organized such that their plus ends are facing the axon terminal while the minus ends reside in the cell body. Thus, the gray cargo is likely to be attached to a dynein motor because it is moving toward the cell body. Because cargo attaches to the tail domains of both dynein and kinesin motors, the attachment of a cargo to either tail is unlikely to affect directionality. Both dynein and kinesin require ATP hydrolysis for their movement.)
What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only? a) The cells would not be able to replicate their DNA. b) The mitotic spindle could not assemble. c) The cells would get larger and larger. d) The cells produced would get smaller and smaller.
d) The cells produced would get smaller and smaller.
Which of the following statements is TRUE? a) The mitotic spindle is largely made of intermediate filaments. b) The contractile ring is made largely of microtubules and actin filaments. c) The contractile ring divides the nucleus in two. d) The mitotic spindle helps segregate the chromosomes to the two daughter cells.
d) The mitotic spindle helps segregate the chromosomes to the two daughter cells.
Which of the following protein families are NOT involved in directing transport vesicles to the target membrane? a) SNAREs b) Rabs c) tethering proteins d) adaptins
d) adaptins (FEEDBACK: Adaptins are involved in vesicle budding and are removed during the uncoating process, and thus should not be present when the vesicle reaches its target.)
The hydrolysis of ATP is necessary for a) The ubiquitin-proteasome pathway b) The endo-lysosomal pathway c) Autophagy d) All of the above
d) all of the above
Which stage of mitosis does this fluorescence micrograph show? a) prophase b) prometaphase c) metaphase d) anaphase
d) anaphase
In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? a) at the transition between G1 and S b) when cells enter G0 c) during M d) at the end of G2
d) at the end of G2
In the electron microscopic micrograph of nutrient-starved mouse embryonic fibroblasts, The double arrows indicate: a) autophagosomes b) proteasome c) mitochondria d) autolysosomes
d) autolysosomes
Which word or phrase below best describes the phase in mitosis depicted in this figure? a) anaphase b) prometaphase c) S-phase checkpoint d) metaphase
d) metaphase
Which of the following statements about lysosomes is TRUE: a) Lysosome is a double-membrane-bound organelle that contains digestive enzymes. b) Lysosomes all look the same under the electron microscope. c) The only molecules that can be digested by lysosomes are proteins. d) None of the above
d) none of the above
Which of the following statements about the structure of microtubules is FALSE? a) Microtubules are built from protofilaments that come together to make a hollow structure. b) The two ends of a protofilament are chemically distinct, with α-tubulin exposed at one end and β-tubulin exposed at the other end. c) Within a microtubule, all protofilaments are arranged in the same orientation, giving the microtubule structural polarity. d) α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.
d) α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments. (α-Tubulin and β-tubulin bind with each other through noncovalent interactions.)
Is the following statement TRUE or FALSE? The concentration of M-Cdk varies in a cyclical fashion during the cell cycle. It peaks at the beginning of the M phase. M-Cdk is degraded via the ubiquitin-proteasome pathway around anaphase, which results in the exit of M phase.
false
The following statement about ubiquitin is true or false? The ubiquitin is a molecule that plays a role in the ubiquitin-proteasome pathway, not in the endo-lysosomal degradation pathway or in autophagy.
false
True or false: The M-cyclin/M-Cdk complex triggers entry into M phase, while the S-cyclin/S-Cdk complex sets the stage for the exit of mitosis.
false
light microscope image
microscope that uses a beam of light passing through one or more lenses to magnify an object
How did they get different mutant strains such as unc-104 (wy873)? (Hint: forward genetics vs reverse genetics)
they were found using forward genetic approaches (genotyping phenotypes)
True or false: Lysosomes are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules
true