iey contract tll eah only just accomplish a chin-up.very slowly, lle Yelevant mu
ID: 560491 • Letter: I
Question
iey contract tll eah only just accomplish a chin-up.very slowly, lle Yelevant muscles perform work at 70 J/kg of musele, what must thefotal massof the muscles be as a percentage of bodv mass 3. Assuming completely efficient encrgy conversion, if a single slow contraction of maximum tension and shortening accomplishes external work of 70 Jkg and the energy available from ATP is 50 J/mmol, then by how much might the concentration of creatine phosphate Jall? HINT: As always, be careful to check that the units cancel out and give the units you need in the answer. toial wecharucal an m mol 4. Most skeletal muscles generate about 20 N of force per cm2 of cross-sectional arca. If a myosin head gencrates 5 pN of force, and a thick filament has about 600 myosin heads, then how many thick filaments are there per cm of cross-sectional area? HINTS: Be careful in converting pN to N, and be extra extra careful in converting 'r tocm Here'san example of how to do the latter. I m-1000 mm. so I m. 1,000,000 mmgrom 1000 x 1000 m
Explanation / Answer
Ans 3
Concentration of creatine phosphate fall
= external work/ATP flux
=( 70 J/kg) / (50 J/mmol)
= 1.40 mmol/kg
Ans 4
Force generated by muscle = 20 N/cm2
A myosin head generates force = 5 pN
600 myosin head generates force = 600 x 5 = 3000 pN
A thick filament generates force = 3000 pN
Convert pN to N (1 N = 10^12 pN)
3000 pN x (1N/10^12pN) = 3 x 10^-9 N
Force generated by a thick filament = 3 x 10^-9 N
Thick filaments/cm2 =
= Force generated by muscle/Force generated by a thick filament
= (20 N/cm2) / (3x10^-9 N)
= 6.666 x 10^9
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