In the model, a thick filament is 16 u long and each thin filament is 10 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.
In the model, a thick filament is u long and each thin filament is u long. A contracted sarcomere is u long.
- How long is its I band?
- How long is its H zone?
- By how much do the tips of the two thin filaments overlap in the middle?
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. Thick: u. Thin: u each. Sarcomere: u.
Plan. The I band is what is left after the A band. The two thin filaments together are u, which is longer than the sarcomere.
Step 1. I band. u.
Step 2. H zone. The thin filaments together cover more than the sarcomere, so no gap is left. The H zone is u.
Step 3. Overlap. u.
Answer: u; u; u.
Check. The H zone and the overlap cannot both be above zero. Here the overlap is above zero, so the H zone is zero.
What if? At a length of u the tips just meet, so the H zone is zero and the overlap is zero too.
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