A relaxed muscle is 33 cm long. Every sarcomere in it is 22 u long…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A relaxed muscle is cm long. Every sarcomere in it is u long. In the contracted muscle, every sarcomere is u long.
- How long is the contracted muscle?
- By what per cent has the muscle shortened?
- What is the length of one thin filament in the contracted muscle?
Need a reminder? The key ideaShow
In the sliding filament theory, the myosin heads bind the actin, pull it toward the centre of the A band and let go when a new ATP binds. The filaments keep their lengths. The A band stays the same, and the I band and the H zone get shorter. In the model, the thick filament is u, each thin filament is u and the relaxed sarcomere is u.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Muscle: cm. Sarcomere: u, then u.
Plan. Use the fraction by which the sarcomere shortens.
Step 1. The length. .
Step 2. The shortening. .
Step 3. The thin filament. The filaments slide and do not shorten. A thin filament is still u.
Answer: cm; ; u.
Check. cm, and .
Watch out. The lengths are in a model. Do not take the number of u as a measured value.
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