Explain why myosin II in a sarcomere can produced force only for that sarcomere contraction and not for that sarcomere extension?

1. a) Why are muscles not in a contracted state all the time? b) Several hours after the death of an animal, a state of rigor mortis, extreme rigidity of the body, occurs. With respect to myosin and actin filaments, why does this occur? What causes the body to relax more later in time? Explain.

Label the molecular components of the myofilaments from a close up view of a model of a relaxed sarcomere

Skeletal muscle cells undergo contractions based on a molecular mechanism involving: 1)the sliding of actin and myosin filaments past each other without any change in filament length  2) the shortening of actin filaments following direct interaction with myosin  3) dynamic instability of microtubules 4)none

List the four primary signal transduction pathways in skeletal muscle.

The ability of myosin to walk along an actin filament may be observed with the aid of an appropriately equipped microscope. Describe how such assays are typically performed. Why is ATP required in these assays? How can such assays be used to determine the direction of myosin movement or the force produced by myosin?

Using the sliding filament theory of contraction, explain why the contraction strength of a muscle is maximal at a particular muscle length.

How does the cross-bridge result in thin filaments sliding over thick for contraction? Use key terms below and identify them on a diagram. cross-bridge formation (need Ca+2), power stroke, detachment (need ATP), reset myosin head

Myosin II action differs from that of kinesin in that one of the kinesin heads is always in contact with a microtubule, whereas both myosin heads become completely detached from the actin filament. How are these differences correlated with the two types of motor activities in which these proteins engage?

Which of the following statements is true?     Fast glycolytic fibers have a small diameter.     Fast glycolytic fibers contain loosely packed myofibrils.     Fast glycolytic fibers have large glycogen reserves.     Fast glycolytic fibers have many mitochondria.