PROBLEM SET 6 MCB2210 Fall 2015 93 Which of the following actin containing structures contains bundles of actin filaments a Filopodia b Lamellipodia c a and b d Stress fibers e a and d 94 As a fibroblast moves its leading edge extends from the cell as a broad flattened protrusion called a a pseudopodium b Lamellipodium c filopodium d podium e podosome 95 How do actin filaments cause the front cell edge to protrude during cell movement a Severing actin filaments at the front cell edge causes a local weakening in the actin cortex that causes the cell membrane to protrude b Polymerization of actin filaments occurs throughout the cell causing it to expand outwards c Increased actin polymerization within the cell body pushes bundles of actin filaments outwards at the front causing it to protrude d An increase in cytoskeletal contractility at the rear of the cell causes a protrusion to squeeze forward at the front e Addition of G actin to the ends of filaments near the plasma membrane forces the membrane to protrude 96 How is an increased rate of actin polymerization localized to the front edge of the moving cell a Activation of Arp2 3 by WASP family proteins near the plasma membrane b Uncapping of actin filaments at the minus ends close to the plasma membrane c Actin filament bundling close to the plasma membrane d Capping of actin filaments at the minus ends near the plasma membrane e All of the above 97 To transport a vesicle that originates from the ER in the periphery of a cell to the Golgi apparatus it would likely be a carried by a motor protein like kinesin I b carried by a motor protein like cytoplasmic dynein c carried by a motor protein like myosin I d diffuse rapidly and in a directional manner e none of the above 98 For a vesicle exiting the Golgi to be secreted it would likely be a transported by a motor protein like kinesin I b transported by a motor protein like cytoplasmic dynein c transported by a motor protein like myosin II 17 d transported by direct diffusion along a microtubule e transported by diffusion along actin 99 For an endosome budding from the plasma membrane to be sent to the Golgi it would likely be a transported by a motor protein like kinesin I b transported by a motor protein like cytoplasmic dynein c transported by a motor protein like myosin II d transported by direct diffusion along a microtubule e transported by diffusion along actin 100 Which of the following does NOT involve actin filaments and myosin motors a A subset of vesicle transport events b Skeletal muscle contraction c Cytokinesis d Stress fiber contraction e All of them involve actin filaments and myosins 101 Which family of GTPases regulate actin assembly a Ran b Rab c Rho d Sar e All of the above 102 Which of the following cytoskeletal systems play a key role in endocytosis a Actin b Microtubules c Intermediate filaments d Septins e All of the above 103 Treatment with nocodazole check your notes will alter the organization of which membranes a Endoplasmic Reticulum b Golgi Apparatus c Nuclear Membrane d Plasma Membrane e a b 104 Which of the following GTPases regulate Formin nucleation activity a Ran regulates Formins b Cdc42 regulates Formins c Ran and Cdc42 regulate Formins d Rho regulates Formins e Cdc42 and Rho regulate Formins 105 What is the third step of those listed below causing lamellipodial protrusion a G protein activation b Arp2 3 becomes activated 18 c A WASP family protein is activated d Actin filament growth is stopped by CapZ e Actin filament elongates 106 The stages through which a cell passes from one cell division to the next constitute the a cell cycle b life cycle c biocycle d energy cycle e regeneration cycle 107 Based on cell activities readily visible in the light microscope there are two major cell cycle phases and a M phase cytokinesis b interphase cytokinesis c M phase G phase d M phase interphase e G phase interphase 108 What evidence suggests that a cell spends the majority of its time in interphase a Interphase is more useful b Only a small percentage of cells in a culture are seen to be in mitosis at any given time c A large percentage of cells in a tissue or cell culture are seen to be in mitosis at any given time d All the cells in a tissue or cell culture are seen to be in mitosis at any given time e Mitosis is too intricate a process to last very long 109 What is the length of interphase for a cell that normally divides once every day a It is about 12 hours long b It is about 2 4 hours long c It is about 48 hours long d It may last for almost the whole day but varies depending on the cell type and growth conditions e It is exactly 22 hours long 110 When do most of the preparations for mitosis occur including such activities as DNA replication a cytokinesis b M phase c interphase d telophase e genophase 111 The period in the cell cycle between the end of DNA replication and the beginning of mitosis is called the phase a G1 b S c G2 d M e G0 19 112 The total length of the cell cycle of cells in a cell culture is 24 hours If M phase is found to be 1 hour S phase is found to be 9 hours and G2 is found to be 4 5 hours How long is G1 a 24 hours b 9 5 hours c 9 hours d 1 hour e 4 5 hours 113 You are assembling tubulin into microtubules in a test tube using a piece of a flagella as a nucleation site After a few minutes fluorescently labeled tubulin subunits are added and the microtubules are visualized in a fluorescence microscope What order of addition will you see a The entire microtubule will be labeled equally b The end will be labeled faster than the end c The end will be labeled faster than the end d Nothing will be labeled e The and end will be labeled at the same rate 114 If you microinject fluorescent tubulin into a cell during G1 phase where would you initially expect to see fluorescence a short time after injection a The plus ends and minus ends of microtubules would be fluorescent b The minus ends of many microtubules would be fluorescent c The plus ends of many microtubules would be fluorescent d The fluorescence would appear uniformly along the microtubules e The microtubules would not become fluorescent 115 If you microinject fluorescent tubulin into a cell during metaphase what pattern of incorporation of fluorescent tubulin would you expect to see over time after injection a Only at the plus ends of microtubules b Only at the minus ends of microtubules c Gradual fluorescence increase over the entire length of the microtubules beginning