muscle contraction

Question 1

why cant actin head bind to myosin when resting

Answer 1

actin-myosin binding site blocked by tropomyosin

Question 2

describe the process of muscle contraction

Answer 2

• influx of ca+ ions depolaries sarcolema
• sarcoplasmic reticulum releases ca+ into the sacrcoplasm
  -ca+ binds to tropomyosin causing it tk cahnge shape adn move out of actin-myosin binding site
• myosin head binds to myosin fillement at actin myosin brinding site forming a cross bridge.
• adp present on the myosin head allows the crosbridge to form
• myosin head bends pulling actin with it causing actin to slide over (sliding filliment theory)
• ADP molecule is released
• adp then binds with pi to form atp
  -ATP bindsto myosin head causing it to change shape and dettach from actin
  -ATPase activated by ca+ ions hydrolses atp back into aadp+ pi releasing energy for myosin head to return to original position