Diagram 16 below shows a cross section of an alveolus in the lung. Rajah 16 di bawah menunjukkan keratan rentas satu alveolus di dalam paru-paru.
Р
R
Q
Diagram16/ Rajah 16
Which of the following is correct about carbon dioxide concentration at P Q and R?
Manakah antara berikut yang benar tentang kepekatan karbon dioksida pada P.
Q dan R?

label a cell membrane

label b cytoplasm

label c ribosomes

label d dna

the membrane forms the outside of the cell

cytoplasm is the liquid within

ribosomes are the components within that distribute rna

the dna is the genetic make-up

the answer is: the „power stroke“ step.

muscle contraction can be divided into a few steps:

1. the release of ach (acetylcholine) in the synaptic cleft, binding of ach for its receptor and consequently opening of the ca channels.

2. the release of ca, binding of ca for the troponin

3. troponin shifting the tropomyosin, which was blocking the active site on the actin

4. myosin heads attaching to actin by breaking down atp to adp+ pi

5.   formation of the ‘cross-bridge’ on the active site of the actin filament by myosin head

6. “power stroke” -the cross bridge pulls actin, which slides over the myosin

9.     7. the release of adp completes the cross-bridge movement and atp attaches to myosin, breaking the actin-myosin cross bridge.