BIOL 1107 Lecture Notes - Lecture 21: Multinucleate, Smooth Muscle Tissue, Mitosis

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2 Dec 2016

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Myosin head can physically move, even though the entire muscle head doesn"t move. Myosin has two active sites- atp binding site and actin binding site. Myosin head is bound to an active binding site. Myosin heads need to slide films that work simultaneously myosin releases from active film when made contact with binding site. Next, atp is hydrolyzed, releasing energy and p(i) is released. This is all a cycle ready to repeat. The protein troponin and tropomyosin in thin filaments. They block the myosin binding sites on the actin. When muscle extends, there is a drop in concentration in calcium(2) in the sarcomeres. Troponin physically overlays the actin so the myosin head cannot interact. When calcium moves into the sarcomere, it binds to the tropomyosin complex and changes it"s shape temporarily. Causes the tropomyosin to twist away and allows for the myosin head to bind. Muscle cell"s cannot create their own action potentials.

Related Questions

Describe the process of skeletal muscle contraction by assembling the following 10 events in the proper order. Your answer must be written in complete sentences- do not just list the letters or the events- write it out. Begin your description with an action potential traveling down a motor neuron and end with the muscle in it's relaxed state.

A) T and T system undergoes a conformational change, exposing the myosin binding sites on actin

B) myosin heads/cross bridges bind to actin and flex, shortening the sacromere

C) the motor neuron triggers an action potential at the neuromuscular junction

D) calcium ions bind to the T and T system

E) actin filaments are pulled toward the center of the sacromere, shortening the muscle fiber

F) muscle fiber is stimulated at the neuromuscular junction

G) myosin head/cross-bridges bind to actin

H) APs travel down the T-tubules to the sarcoplasmic reticulum

I) in response to an AP, calcium ions are released into the cytosol/space around the myofibrils

J) calcium ions actively transported into the sarcoplasmic reticulum

K) myosin head continues to attach, flex, release, extend, and reattach as long as calcium ions are present

lilacporcupine860

1)Describe the directions in which the two motor proteins, kinesin and dynein, travel along a microtubule. Which of the two proteins moves materials towards the Golgi and which moves materials away from the Golgi? Lastly, what is the speed of kinesin dependent on?

2)What are microfilaments crucial for? How do they self-assemble? Which end do they prefer to elongate from?

3)Describe what types of filaments are in each of the bands of the sarcomere. As a muscle fiber is shortened, describe what happens to each of the bands in the sarcomere as the Z lines move inwards.

4)Describe the role of calcium ions in muscle contraction.

5)List the various types of actin-binding proteins

6) A. What are 3 functions of the cytoskeleton?

B.What are the three filaments that compose the cytoskeleton, and what are they composed?

7)How do they see the internal structures of cells in the microscope? What do proteins get labeled with?

8)Myosin II action (Figure 9.61) differs from that of kinesin (Figure 9.15) 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?

9)If a myofibril were pulled so that the sarcomeres increased in length by approximately 50 percent, what effect would you expect this to have on the contractile ability of the myofibril? Why? What effects would this have on the H, A, and I bands?

10)Because cytoplasmic vesicles are seen to move in both directions within an axon, can you conclude that some microtubules are oriented with their plus end facing the axon terminus and others oriented with the opposite polarity? Why or why not?

BIOL 1107 Lecture Notes - Lecture 21: Multinucleate, Smooth Muscle Tissue, Mitosis

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