A-LevelBiologyControl and coordination9700/42 · Oct/Nov 2018 · Q49 Marks

[Figure 4.1] shows a transmission electron micrograph of a section through striated muscle.

(a)Complete Table 4.1, using the letters A, B or C, to show the location of proteins associated with striated muscle structure. You may use each letter once, more than once, or not at all. Table 4.1 protein | location -----------------|--------- myosin and actin | actin alone | ATP synthase | ATPase | [4]
(b)Explain the role of ATP in the contraction of striated muscle.[5]

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Mark scheme

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[4] protein location myosin and actin B ; actin alone C ; ATP synthase A ; ATPase B ;
[5] any five from 1 myosin binding site exposed then 2 myosin head, binds to actin / forms cross bridge ; 3 ADP released causes motion of myosin head; 4 actin moved; 5 power stroke ; 6 ATP binds to myosin head; A cross bridge broken 7 (myosin head / ATPase) causes, hydrolysis of ATP / ATP → ADP + Pi ; 8 myosin head moves back to original position / AW ; 9 (ATP needed) to pump Ca2+ back into sarcoplasmic reticulum ;

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