<span>a. a substance that is naturally found in the brain</span>
Answer:
The earth is like an egg inside of the earth is layered something like an egg. Both have a thin, brittle shell. The crust of the earth is broken into pieces, like the cracked shell of a hardboiled egg. the mantle of the earth is like the egg white and the core of the lies in the center, like the egg yolk.
Explanation:
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I think this view is NOT compatible with either of these hypothesis illustrated above. This is because each hypothesis presents prokaryotes as two separate groups. Prokaryotes are unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane bound organelle unlike the eukaryotes which has the membrane bound nucleus and other organelles.
<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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