BIO353_ Exam 2 Short Answers and questions revised edition 2023/2024

BIO353: Exam 2 Short AnswersModule 11: Actin Filaments 1.Draw an actin monomer and an actin filament and label all the parts, molecular weights,etc..2.Explain the geography of actin filaments. Explain the geography of stress cable, filapodiaand lamelliapodia in a cell, and locomoting in a culture plate.a.Actin filaments are located under the plasma membrane on the inside of the cell. Stresscables as well as filopodia and lamellipodia are located near the plasma membrane. 3.Focusing on actin monomers and actin filaments: explain what occurs when a cell reversesits direction by 180 degrees.a.When a cell reverses its direction by 180 degrees, there is a reverse displacement for theactin and myosin filament. There is an increase in the movement and contraction of thefilaments in direction towards each other. Due to the complete 180 degree reversal andthe presence of the extended N-terminus in the myosin, it will tend to block the complete180 degree swing of other myosin and hence it might lead to interruption in the functionof the muscles. Due to the reversal, the actin monomer tends to fall in the same directionand tends to make the muscle more polar. 4.Explain how the binding of ATP affects cytoskeletal monomers. Explain how the function ofcytoskeletal networks can change depending on reversible binding of cytoskeletonassociated proteinsa.Hydrolysis of ATP to ADP helps identify the assembly vs disassembly end with an ATP"cap" on the assembly end and an ADP "cap" on the disassembly end. With ATP present,the monomer changes shape and promotes self-assembly into the actin filament. WhenATP is hydrolyzed to ADP, it changes the conformation of the monomer making it less suited to fit into an actin filament. Position of ATP gives the monomer a polarity thatsteps up the polarity of the actin filament.5.Describe how myosin II can be made into a tool to analyze the different polarities of actinfilaments in the cell.a.Myosin II can be made into a tool by scientists using biotechnology to determine theorientation of an actin filament in stress cables by the winding of the heavy and lightchains. 6.Draw the structure of a myosin II molecule when its light chains are not phosphorylated.7.Explain the geography of actin filaments as it relates to a living cell.8.Explain how myosin II can be made into a tool by scientists using biotechnology. Andexplain how this can be used to determine the orientation of an actin filament in:s cables - anti-parallel bundles of actin filaments, hence the myosin barbs will pointin opposite directions along the two filaments.b.Filopodia - the barbs will all be directed at the tip as that is the positive end of the actin(polymerizing/growing end) 9.Explain what cell permeabilization is.a.Making holes in the cell to let aqueous solutions of cleaved myosin heads in. Done with anon-ionic detergent and isotonic buffer. Module 13: Microtubules