<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:
glutamic acid, because the R group could form ionic bonds
arginine, because the R group could form ionic bonds
tryptophan and tyrosine, because the R groups are small, allowing close stacking
glycine and alanine, because the R groups are small, allowing close stacking
<span>carbon enters the biotic part of the ecosystem namely plants from the atmosphere through PHOTOSYNTHESIS </span><span />
The correct answer is - C) carotenoids.
The majority of the trees from the mid-latitude forests tend to shade their leaves in the autumn. This process occurs because of the seasonal changes in the climate, where the trees tend to be almost not-active during the winter, so in order to preserve as much energy and nutrients as possible they get read off their leaves.
It is not a sudden process, but it takes some time, where the leaves from the initial green color start to change to yellowish, than towards orange, reddish, or brownish before they fall.
The reason why this coloration appears in the leaves when the tree starts to process of shading them off are carotenoids. The carotenoids found in the leaves, the lutein and the beta-caroten, thorugh the xantophills and the flavonoids give a yellowish color to the leaves, thus we get the beautiful autumn colors and landscapes.
