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Unformatted text preview: CBIO / BIO L 3400 SPRING 2011 THIRD QUIZ Probl e m grad e d by J . Blak e Norman . Con t a c t a t [email protected] . e du wi t h qu e st ion s or c on ce rn s . For r e grad e r e qu e sts : in c lud e in your e mail a full d e s c rip t ion (argum e n t ) for your an s w e r . Grading r e qu e sts mu st origina t e from your offi c ial UGA e mail addr e ss for r e vi e w . Digi t al c opi e s of st ud e n t e xam s ar e main t ain e d t o r e f e r e n ce your r e qu e sts . QUESTION 1 – 25 POINTS a. (5pt o f po ss ibl e 6p t ) Describe (draw) the organization of a sarcomere with particular attention to the polarity of protein filaments, and explain how this organization promotes muscle contraction. Name at least one distance along the sarcomere that changes during contraction and one that stays the same. 1. Constant Length: A-band; Actin Filament; Myosin Filament 2. Shortening Length: Z-band to Z-band 3. Myosin bipolar in center between actin filaments 4. Actin polar with all plus ends at Z-bands 5. Myosin is a plus end directed motor 6. Myosin pulls actin with minus ends leading shortening sarcomere b. (15pt) Compare and contrast the structure and function of myosin II and kinesin including their biological roles in non-muscle cells, interactions with cytoskeletal filaments, and mechanism by which they interact with filaments and nucleotide to produce force. Myosin II Kinesin Roles Cytokinesis (1) Locomotive Tail Contraction (1) Organelle Transport (1) Mitosis (1) Interactions Actin (1) + end directed (except Myosin VI) (1) Microtubules (1) Most + end directed; few – end (1) Nucleotide ATP hydrolyzed to ADP + Pi (1) ATP hydrolyzed to ADP + Pi (1) Mechanism ATP bound form low affinity. (.5) Heads independent. (.5) Lever arm projects from head. (.5) Not Processive. (.5) Binds actin for small time of cycle. (.5) ATP bound form high affinity. (.5) Heads work cooperatively. (.5) Neck linker swings 2 nd forward. (.5) Highly Processive. (.5) Binds MT for large time of cycle. (.5) c. (5pt) Explain the mechanism by which the interaction of actin and myosin in skeletal muscle is regulated by calcium. 12. Actin linkage regulation by tropomyosin (TM) and troponin (TN) bound to actin. Tropomyo s in (TM) and Troponin (TN) on e poin t e a c h . 3. At low calcium, Tn (I,T,C) holds TM at distal edge of actin filament blocking myosin. 4. At high calcium TnC binds calcium, changes conformation along with TnT and TnI....
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- Spring '08
- actin binding proteins, Tim 17/PAM16, actin filaments Actin