1. The figure below shows the ultrastructure of a myobril. Identify the labelled regions.
Answer
1 = A band,
2. What is the role of calcium ions in muscle contraction ?
Answer
Calcium ions bind to troponin, causing tropomyosin to shift and expose the myosin-binding sites on the actin filament, allowing a cross-bridge to form.
3. The figure below is a diagram showing the structure of a sarcomere. Identify parts X and Y in the diagram.
Answer
X = myosin, Y = actin
4. Describe what happens to A band, I band and H zone when the sarcomere contracts.
Answer
The A band remains the same length, while the I band and H zone become shorter.
5. The figure below shows sections of a sarcomere at three different positions. Identify which position the section has been taken from and explain its appearance.
Answer
X = in the A band because it is showing both myosin and actin filaments.
Y = I band because only the thin actin filaments are visible.
Z = H zone because only the thick myosin filaments are visible.