| Date | May 2013 | Marks available | 1 | Reference code | 13M.1.HL.TZ1.37 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Question number | 37 | Adapted from | N/A |
Question
What is the role of ATP during contraction of a skeletal muscle fibre?
A. To uncover the myosin binding sites on actin filaments
B. To make cross-bridges between actin and myosin filaments
C. To break cross-bridges and re-set myosin heads
D. To cover the myosin binding sites on actin filaments
Markscheme
C
Examiners report
In question 37 a substantial minority of candidates thought that ATP is used to make cross bridges rather than break them. The development of rigor mortis is an indicator that energy from ATP is directly used to break rather than make cross bridges.
