muscle contaction

Question 1

describe myosin filaments

Answer 1

globular hinged head so can move back and forth

atp binding site and actin binding site

Question 2

describe actin filaments

Answer 2

have binding site for myosin heads called actin myosin binding site

Question 3

where is tropomyosin found

Answer 3

between actin filaments helps to move myofilaments past each other

Question 4

describe actin myosin binding site in resting state

Answer 4

blocked by trypomyosin

-so myofilaments cannot slide past each other as myosin heads cannot bind to actin

Question 5

describe muscle contraction

Answer 5

1- action potential from motor neurone stimulates muscle cell

2- depolarisation spreads down t tubules to sarcoplamic recticulum

3-causes release of calcium ions from sarcoplasmic recticulum into sarcoplasm

4-calcium ions bind to protein on trypomyosin causing shape change pulling trypomyosin out of actin myosin binding site

5-exposes binding site so myosin head binds - actin myosin cross bridge

6-calcium ions also activate atp hydrolase which turns atp- adp and pi to provide energy for contraction

7-energy release from atp causes myosin head to bend pulling actin filaments in rowing mechanism

8-another atp molecule provides enrgy to break actin myosin cross bridge so myopsin head detaches after it moves

9- myosin head then reatatches to other binding site and cycle repeats

10-many cross bridges form and break rapidly causing shorten sacromere and msucle contracting

11- cycle continues as long as calcium ions present