Sliding Filament Theory

Question 1

Describe the features in a resting muscle..

Answer 1

• Tropomyosin blocks the myosin head from binding to the actin-myosin binding site.
• Therefore preventing myofilaments from sliding past each other.

Question 2

Describe the sliding filament theory….

Answer 2

1) Action potentials reaches the neuromuscular junction.
2) Acetylcholine diffuses over to the post-synaptic mebrane, binding to receptors.
3) A wave of depolarisation spreads along T-tubules and the sarcoplasmic reticulum.
4) Sarcoplasmic reticulum releases calcium ions into the sarcoplasm.
5) Calcium ions bind to troponin, causing it to change shape and this pulls tropomysoin out of the actin-myosin binding site.
6) Myosin head is now able to bind to the actin-myosin binding site to form an actinmyosin bridge.
7) ATP hydrolase is activated and hydrolyses an ATp that is bound to the myosin head.
8) Energy released causes myosin head to bend.

Question 3

What is the role of phosphocreatine?

Answer 3

• Provides an extra phosphate molecule which can be used to synthesise ATP.

Question 4

Negative of phosphocreatine?

Answer 4

• Short term supply