<span>There are numerous proteins in muscle. The main two are thin actin filaments and thick myosin filaments. Thin filaments form a scaffold that thick filaments crawl up. There are many regulatory proteins such as troponin I, troponin C, and tropomyosin. There are also proteins that stabilize the cells and anchor the filaments to other cellular structures. A prime example of this is dystrophin. This protein is thought to stabilize the cell membrane during contraction and prevent it from breaking. Those who lack completely lack dystrophin have a disorder known as Duchene muscular dystrophy. This disease is characterized by muscle wasting begininng in at a young age and usually results in death by the mid 20s. The sarcomere is the repeating unit of skeletal muscle.
Muscle cells contract by interactions of myosin heads on thick filament with actin monomers on thin filament. The myosin heads bind tightly to actin monomers until ATP binds to the myosin. This causes the release of the myosin head, which subsequently swings foward and associates with an actin monomer further up the thin filament. Hydrolysis and of ATP and the release of ADP and a phosphate allows the mysosin head to pull the thick filament up the thin filament. There are roughly 500 myosin heads on each thick filament and when they repeatedly move up the thin filament, the muscle contracts. There are many regulatory proteins of this contraction. For example, troponin I, troponin C, and tropomyosin form a regulatory switch that blocks myosin heads from binding to actin monomers until a nerve impulse stimulates an influx of calcium. This causes the switch to allow the myosin to bind to the actin and allows the muscle to contract. </span><span>
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Answer:
C
Explanation:
The gravity of the sun and moon pull on the water of the oceans of the earth hence causing a bulge of these waters at the point on earth where the moon is above. The region where the moon is above, and the opposite side on the earth, will therefore experience high tides while the places at right angles (on the surface of the earth in relation to the moon position) will experience low tides.
The answer is False. Stalagmite is a cone-shaped <span>deposit of calcite that builds up on the floor of a cave.
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Answer:
La diferencia entre un iceberg y un glaciar es que el iceberg es la pieza de un glaciar que se desprende (o se rompe) cuando las temperaturas suben. Los glaciares están formados por una gran masa de mezcla de nieve y hielo que cubre el fondo del valle de una cadena montañosa.
Explanation:
Answer:
The ten percent law states that the total energy content of a trophic level in an ecosystem is only about one-tenth (or 10%) that of the preceding level. The trophic levels of any ecosystem can be arranged in a pyramid shape to show the amount of energy available to support one trophic level to the next.
