6.4 Muscles

Question 1

describe how the banding pattern will be different when muscle fibre is contracted

Answer 1

H zone narrows
I band narrows
z line moves closer together
sarcomere shortens

Question 2

explain the importance of ATPase during muscle contraction

Answer 2

hydrolyses ATP into ADP + Pi and releases energy

energy used to form and break actomyosin bridges

Question 3

I band

Answer 3

actin

Question 4

A band

Answer 4

Actin and myosin overlap

Question 5

H zone

Answer 5

only myosin

Question 6

M line

Answer 6

middle of myosin

Question 7

what happens to I band during muscle contraction

Answer 7

shortens

Question 8

what happens to H band during muscle contraction

Answer 8

shortens and dissapears

Question 9

what happens to A band during muscle contraction

Answer 9

stays the same

Question 10

describe the role of calcium ions in the contraction of a sarcomere

Answer 10

causes movement of tropomyosin
to reveal binding site on actin
allowing myosin head to bind to actin
which activates ATP hydrolase

Question 11

describe the role of calcium ions and ATP in the contraction of a myofibril

Answer 11

calcium ions enyer myofibril from sarcoplasmic reticulum

this causes tropomyosin to move and expose binding site on actin

myosin head binds to exposed binding site on actin

hydrolysis of ATP causes myosin head to bind which pulls on actin molecules

attatchment of new ATP to each myosin head causes myosin head to detatch