11.2
Explain how calcium is involved in muscle contraction. (3)
Action potential causes release of calcium from sarcoplasmic reticulum. Calcium ions bind to troponin, causing tropomyosin to move from binding sites. Exposes myosin binding sites on actin.
What is the role of calcium in muscle contraction?
To bind to troponin so myosin-binding sites on actin are exposed
Explain the role of ATP in muscle contraction. (2)
a. ATP binds to myosin heads;b. ATP used to break cross bridges;c. energy released when ATP forms ADP and phosphate;d. myosin head reset;e. actin slides over myosin; c.
Explain the role of calcium in muscle contraction. (3)
ction potential/nerve impulse/motor neuron causes release of calcium; calcium released from sarcoplasmic reticulum; calcium causes binding sites on actin to be exposed; myosin heads bind to binding sites/to actin and push actin (inwards);
Outline the function of myosin and actin in muscle contraction. (3)
a. formation of cross-bridges/myosin binds to the thin filament/actin;b. Z-bands pulled towards each other;c. sliding of actin and myosin filaments/shortening the sarcomere/I-band;d. use of ATP to break cross-bridges / myosin releases actin when binding to ATP;e. myosin heads re-set;f. contraction ceases when myosin head detaches from the thin filament;
Coughing to clear the airways is accomplished by muscle contractions. Explain muscle contraction. (8)
a. myofibrils «in muscle fibers/cells» b. sarcomeres «are the repeating units in muscle/myofibrils» c. sarcomeres arranged end to end / sarcomeres shorten during muscle contraction d. actin and myosin/overlapping protein filaments/diagram to show sarcomere with actin and myosin overlapping e. dark and light bands «in sarcomeres»/diagram to show this/light bands narrower when muscle is contracted f. thick filament is myosin and thin filament is actin/diagram to show this g. nerve impulses stimulate contraction/cause depolarization of sarcolemma/T-tubules/trigger release of calcium from sarcoplasmic reticulum h. calcium ions released from sarcoplasmic reticulum/bind to troponin i. troponin causes tropomyosin to move/exposes binding sites on actin j. myosin «heads» form cross bridges with/bind to actin k. myosin heads move/change angle/swivel/cock / myosin heads cause the power stroke l. myosin filaments pull actin towards center of sarcomere/more overlap between actin and myosin/Z-lines move closer m. ATP is used «to provide energy»/cause cross-bridges to break/cause movement of myosin heads/cause filaments to slide/cause muscle contraction n. intercostal/abdominal/diaphragm muscles contract «to cough»
