<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:
it allows only some materials to pass through and leave the cell.
Polysaccharides have 1 sugar
disaccharides have 2 sugars
monosaccharides have a chain of sugars
Chromosomes carry genetic information of the organism
Genes transfer genetic information from parent to offspring
arisen by mutation, and found alongside chromosomes
The domain Eukarya evolved from the unicellular organisms, and the proof of this can be derived from the endosymbiotic theory. According to this theory, the organelles, such as mitochondria and chloroplasts were previously free-living organisms. This is supported by the fact that the mitochondria and chloroplasts have their own DNA (deoxyribonucleic acid).
Hence, the answer is 'Option C - mitochondria and chloroplasts have their DNA.'
