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Cell Bio- Exam 2
study for final
| Question | Answer |
|---|---|
| The term ―dynamic instability‖ refers to the fact that microtubule plus ends, unless stabilized, will constantly be either growing or rapidly shrinking. | True |
| v-SNARE—t-SNARE interactions serve to both create specificity of targeting of vesicles to correct destination membranes and to position the membranes of transport vesicles close to that of the target membrane so they can dock or fuse more efficiently. | True |
| Plasma membrane proteins found in endocytic vesicles can traffic back, or ―recycle‖ to the plasma membrane from the endosome, rather than continuing to the lysosome. | True |
| Integrins are proteins which permit adhesion of crawling/motile cells to substrates and help organize the actin cytoskeleton at their sites of activation within such cells. | True |
| Among the three types of cytoskeletal filaments, the least dynamic are: | Intermediate Filaments |
| The lysosome of a cell contains a variety of protein and enzyme factors that enable the: | Degradation/Hydrolysis of nucleic acids, proteins, and oligosaccharides |
| Nuclear lamins are a class of intermediate filaments that are regulated by cell division signals to break down and reform the eucaryotic nucleus during mitosis. Lamin assembly is regulated by: | Phosphorylation on Ser, Thr, Tyr residues |
| A class of proteins that function in the ER as a ―quality control‖ for protein folding are: | Chaperones |
| Signal sequence in secreted eucaryotic protein is to be recognized by which pauses translation by the ribosome until it is docked on membrane where nascent polypeptide can be translocated into lumen of that compartment by translocation channel. | Signal Recognition Particle (SRP); Endoplasmic Reticulum (ER) |
| FRAP is , while FRET is . | A method for determining protein mobility; A method for determining the proximity of two proteins |
| When visualizing proteins in thin section EM via antibody decoration, the antibodies are typically visualized in the electron microscope by: | Gold particles/beads that are bound to the antibodies |
| The specialized functions of different membranes are largely determined by the __________________ they contain. Membrane lipids are __________________ molecules, composed of a hydrophilic portion and a hydrophobic portion. | Proteins; Amphipathic |
| An ER/secretory pathway sorting signal in proteins: | Will be found at the amino (N) terminal end of the protein; Will sometimes be cleaved from the mature protein after import of the protein to the ER |
| To determine whether a plasma membrane protein is subject to posttranslational modification (for example, phosphorylation or ubiquitylation, the best approach would be to: | Detergent extract followed by MALDI-TOF(Matrix Assisted Laser Desorption Time of Flight) mass spectroscopy |
| What is the role of the nuclear localization sequence in a nuclear protein? | It is bound by a receptor in the cytoplasm that directs the nuclear protein to the nuclear pore |
| Which of the following is the least common event for a membrane phospholipid? | Flipping to the opposite leaflet |
| A microtubule bound to the centrosome and in the process of shrinking is severed in half. The ends of the two microtubules exposed at the severed site and at the end originally shrinking are such that: | GDP is bound to the alpha:beta heterodimers |
| Profilin is an actin monomer sequestering protein. Suppose that you obtain a mutation in the gene encoding this protein that causes the protein to bind actin with higher affinity (i.e. more tightly). This type of mutant would best be described as a: | Gain of function mutant of profilin |
| You are interested in identifying new components or regulators of nuclear pores and their assembly in cells. The experimental method(s)or approach(es) that would do this best would be: | Mass spectrometry of nuclear pore proteins isolated from nuclear membranes; a genetic screen looking for suppressors of a conditional mutant of a nuclear pore protein |
| A structural analog of GTP exists, GMPPNP, cannot be hydrolyzed to GDP+Pi-blocks or poisons reactions dependent on this activated carrier for E. Which in vitro assays would you expect to be blocked or inhibited by addition of GMPPNP to the reaction. | Nuclear import of a protein |
| Which of the following membrane components does not contain a fatty acid tail? | a. Phosphatidylcholine b. A glycolipid c. Phosphatidylserine d. Cholesterol -All of the above contain fatty acid tails |
| A protofilament of a microtubule has inherent polarity with respect to the arrangement of the proteins comprising it. | True |
| Transmembrane domains of proteins can associate with the lipid bilayer through their adoption of an alpha helical structure exposing mainly hydrophobic R groups of the region comprising the helix to the surrounding lipid bilayer. | True |
| Cytokinesis of plant cells occurs via a phragmoplast whose formation involves microtubules and components of the Golgi. | True |
| To determine the mobility of a plasma membrane receptor protein, the best approach would be a: | FRAP (Fluorescence Recovery After Photobleaching) experiment |
| Which of the following is the least common event for a membrane phospholipid? | Flipping to the opposite leaflet |
| Which type of cytoskeletal filament(s) are said to possess dynamic instability? | Microtubules |
| proteins for vesicles serve to help provide the energy to deform the underlying membrane during the process of vesicle formation. | Coat |
| The internal compartments of the eukaryotic cell are believed to have originated: | Such that the ER, Golgi and endosomes are believed to be derived from invaginations of the plasma membrane that became stabilized |
| Which of the following changes take place when a skeletal muscle contracts? | The sacromeres have become shorter. |
| In crawling cells, are finger-like extensions of the plasma membrane produced by actin polymerization. Polymerization of actin in these structures often occurs in response to the activities of proteins. | Filopodia; Rho and formin |
| Addition dynamics of both actin molecules and alpha:beta tubulin heterodimers to the growing ends of their respective filaments in cells are intrinsically regulated by: | Nucleotide binding and Hydrolysis |
| During mitosis, kinetochores: | Bind to microtubules to aid chromosome segregation |
| A class of proteins that function to move phospholipids between the two leaflets of a membrane bilayer are: | Flippases |
| Proteins destined to enter the endoplasmic reticulum | Begin to cross the plasma membrane while still being synthesized |
| Why are glycolipids and glycosylated regions of proteins found on the extracellular, but not the cytoplasmic, surface of the plasma membrane? | The enzymes that add the sugar groups are confined to the inside of the endoplasmic reticulum and the Golgi apparatus. |
| What is the role of the nuclear localization sequence in a nuclear protein? | It is bound by a receptor in the cytoplasm that directs the nuclear protein to the nuclear pore. |
| Nuclear lamins are a class of intermediate filaments that are regulated by cell division signals to break down and reform the eucaryotic nucleus during mitosis. Lamin assembly/disassembly is regulated by: | Phosphorylation on Ser, Thr or Tyr residues |
| A nucleating function for microtubules is performed by which is an important part of the . | Gamma tubulin; Centrosome |
| Rab proteins and tethers: | Function along with v-SNAREs and t-SNAREs to dock vesicles at appropriate compartments |
| ARPs: | Nucleate actin filaments |
| After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode? | ER membrane proteins, Plasma membrane proteins and soluble secreted proteins |
| The disease progeria is caused by mutations in which type of protein? | Nuclear Lamin Proteins |
Created by:
Ash T.
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