13.10 Sliding Filament Model

Question 1

What happens to filaments during contraction?

Answer 1

Myosin filaments pull actin filaments inwards to the centre of the sarcomere
Light band becomes narrower
Z lines move closer together, sarcomere shortens
H zone becomes narrower

Question 2

Structure of myosin

Answer 2

Contain globular heads that are hinged - allows movement backwards and forwards
On the head, there is a binding site for actin and ATP

Question 3

Structure of actin

Answer 3

Contain binding sites for myosin heads
These binding sites are usually blocked by tropomyosin - held in place by troponin

Question 4

What is a neuromuscular junction?

Answer 4

Point where a motor neurone and a skeletal fibre meet

Question 5

How is energy supplied during muscle contraction?

Answer 5

Hydrolysis of ATP into ADP and phosphate

Question 6

Why is energy required during muscle contraction?

Answer 6

Movement of myosin heads
Allow sarcoplasmic reticulum to actively reabsorb Ca2+ ions from the sarcoplasm

Question 7

How is ATP generated?

Answer 7

Regenerated from oxidative phosphorylation of ADP (takes place when there is O2)
ATP made by glycolysis - pyruvate is converted into lactate in anaerobic respiration
Creatine phosphate - reserve supply of phosphate, combines with ADP to reform ATP. Generates ATP quickly, but phosphate used up quickly and the store is replenished using phosphate from ATP