Cell Biology (BIO 353)- Exam 2 Practice Questions and Answers

Cell Biology (BIO 353)- Exam 2 Practice Questions and Answers Actin filaments: a) have a diameter of 7 nm and contain 375 amino acids. b) are composed of 2 subunits each of molecular weight of 42 kDa. c) have a diameter of 7 nm and contain 450 amino acids. d) have no polarity. e) have GTP in each of the monomers. f) The correct answer is not listed. - Ans:-f) The correct answer is not listed. Actin filaments will a) undergo treadmilling in a test tube. b) undergo treadmilling in a living cell. c) never reach equilibrium. ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 2/23 d) two of the above. e) none of the above. - Ans:-d) two of the above. The number of amino acids in an actin monomer is: a) 375 b) 450 c) 460 -780 d) 750 f) none of the above - Ans:-a) 375 Hydrolysis of ATP to ADP: a) helps identify the assembly vs the disassembly end b) is used in dynamic instability c) has a role when the actin filament is in chemical equilibrium with the actin filament monomers d) is important for the nucleation site ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 3/23 e) none of the above - Ans:-a) helps identify the assembly vs the disassembly end Actin filaments associate with a nucleotide triphosphate. a) True b) False - Ans:-a) True Treadmilling of actin filaments only occurs in a test tube. a) True b) False - Ans:-b) False Preassembled nucleation sites in a living cell are equivalent to the intracellular preference for actin filaments a) True b) False - Ans:-a) True Intracellular preference for actin filaments : a) is a way to look a the geography of the cell and the role of the nucleus. b) is a way to look at the geography of the cell and show where the role of actin filaments is important. c) explain how actin gets into the nucleus. ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 4/23 d) explain how the Golgi Apparatus forms. e) two of the above. - Ans:-b) is a way to look at the geography of the cell and show where the role of actin filaments is important. The ability of actin filaments to disassemble into small monomers: a) enables the building blocks of actin filaments to move from one side of the cell to the other. b) is not relevant to actin filaments. c) is relevant to treadmilling. d) two of the above. e) none of the above - Ans:-d) two of the above. What causes a myosin II molecule to be able to form a bipolar fiber? a) Myosin I. b) Myosin - like chain kinase. c) Calcium binding to calmodulin. d) Two of the above. e) Three of the above. - Ans:-c) Calcium binding to calmodulin. ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 5/23 The diameter of the actin filament is ...... nm - Ans:-7 nm Draw an actin monomer and an actin filament and label parts. molecular weights, ect. - Ans:-Actin filaments have diameter of 7 nm and can be various lengths in the cell, depending on the number of monomers present in the linear array of actin filaments. The monomers are proteins that have a globular/dumbbell shape. The monomer has a molecular weight of 42 kD and is composed of 375 amino acids. Explain the geography of actin filaments. Explain the geography of stress cable, filapodia and lamelliapodia in a cell, and locomoting in a culture plate. - Ans:-Actin filaments are greatly enriched at the cell periphery in both motile and non-motile cells. Filapodia and Lamellipodia are located near the plasma membrane. Describe the physical and chemical properties of the monomer and polymer of actin, filaments. Explain how a) actin filaments assemble and disassemble. Classify b) actin filaments, based on their ability to treadmill. - Ans:-a) The nucleation site of actin filament occurs followed by a decrease in concentration of tublin monomers with a decrease ingrowth leading to chemical equilibrium. When ATP is present in the monomer, the monomer has a conformation that promotes its self-assembly into an actin filament, assuming the monomer concentration is high enough. Focusing on actin monomers and actin filaments: explain what occurs when a cell reverses its direction by 180 degrees. - Ans:- ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 6/23 Explain how the binding of ATP affects cytoskeletal monomers. Explain how the function of cytoskeletal networks can change depending on reversible binding of cytoskeleton associated proteins - Ans:-ATP is present in the monomer. The gamma phosphate of ATP is hydrolyzed to form ADP, the absence of a third gamma phosphate causes a conformational change of the monomer to form a less suited to fit an actin monomer. The position of ATP along the cleft of the monomer gives it polarity. Actin filaments will only assemble in parallel bundles. a) true b) false - Ans:-a) false Describe how myosin II can be made into a tool to analyze the dif