Muscle Cells Lab Report

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Some of the most important organs in the human body are muscles. Muscles usually make up 30-50% of the body and are responsible for producing skeletal movement, maintaining body position, and regulating body temperature. In a lab, the process of muscle contraction was investigated by exploring the sliding filament theory. An experiment was conducted to determine whether muscle length played a role in the amount of force a muscle produces. In order to fully understand how a muscle contracts, it is necessary to first understand the structure of muscle cells. Muscles cells are large cells that are surrounded by a special membrane called the sarcolemma and are filled with fluid called sarcoplasm. The sarcoplasm abounds with mitochondria for energy production and ribosomes for protein manufacturing. Muscle cells are also packed with many
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Once the bridges are formed, the myosin pulls on the actin contracting the muscle. Cross bridge formation can only occur, however, when the binding sites on the actin are free. Calcium ions work to free up the myosin binding sites on actin. When a muscle is relaxed, a protein called tropomyosin blocks the myosin binding site. Calcium rushes into the cell and attaches to a special protein troponin when a muscle is stimulated by a nerve cell. The troponin then changes shapes and pulls the tropomyosin off the binding site. This frees up the binding site allowing myosin to attach. Sarcomere length can also have a major effect on the amount of force generated by the contraction when sarcomeres are significantly shortened; the actin and myosin get crowded and have trouble producing strong contractions. When sarcomeres get excessively stretched, the myosin gets pulled in the wrong direction preventing it from binding to the actin. This decrease in cross bridge formation results in a much weaker

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