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Question 18M.2.HL.TZ1.c

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Date May 2018 Marks available [Maximum mark: 7] Reference code 18M.2.HL.TZ1.c
Level HL Paper 2 Time zone TZ1
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 7]
18M.2.HL.TZ1.c

Explain the process of muscle contraction.

[7]

Markscheme

a. muscle fibre contains many myofibrils 

b. made up of sarcomeres/labelled diagram showing one or more sarcomeres 

c. nerve impulse/signal from (motor) neuron causes release of calcium (ions)/Ca2+ 

d. calcium (ions)/Ca2+ released from sarcoplasmic reticulum 

e. calcium (ions)/Ca2+ link to troponin 

f. tropomyosin moves to expose actin binding sites 

g. ATP hydrolysis/ATP to ADP and phosphate/release of phosphate from ATP 

h. ATP binds to myosin heads and causes them to cock/change angle/release/gain energy 

i. myosin heads bind/form cross-bridges to actin 

j. myosin heads push on actin and then detach from actin 

k. actin moved towards centre of sarcomere/sliding of filaments 

l. sarcomere becomes shorter (resulting in muscle contraction)

Accept any mark point if clearly made on an annotated diagram.

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