place the following in order (1-11):
Myosin heads bind to active sites on actin molecules
ATP is hydrolyzed
Myosin heads return to their high-energy shape(******), ready for the next working stroke
Calcium ions bind to troponin
Cycling continues until calcium ions are sequestered by the SR
Myosin cross bridges detach from actin
Troponin changes shape
ADP & Pi(inorganic phosphate) are released from the thick filament
Myosin heads pull on the thin filaments(working stroke) & slide them toward the center of sarcomere
ATP binds to thick filament
Tropomyosin is moved into the groove between the F-actin strands exposing active sites on actin
To put the given statements in order, you first need to understand the steps involved in muscle contraction. Here are the steps involved in muscle contraction, including the statements you provided:
1. Calcium ions are released from the sarcoplasmic reticulum (SR) in response to a nerve impulse.
2. Calcium ions bind to troponin, causing it to change shape.
3. Troponin's shape change moves tropomyosin into the groove between the actin filaments, exposing the active sites.
4. Myosin heads bind to the active sites on actin molecules.
5. ATP, which is already bound to the myosin heads, is hydrolyzed into ADP and Pi (inorganic phosphate). This provides energy for the working stroke.
6. Myosin heads pull on the thin filaments (working stroke) and slide them toward the center of the sarcomere.
7. ADP and Pi are released from the thick filament.
8. ATP binds to the thick filament, causing myosin to release from actin.
9. Myosin heads return to their high-energy shape for the next working stroke.
10. Cycling of steps 4-9 continues until calcium ions are sequestered back into the sarcoplasmic reticulum.
11. The muscle relaxes, and the sarcomere returns to its resting state.
Now, let's put the statements you provided in the correct order:
1. Calcium ions bind to troponin.
2. Troponin changes shape.
3. Tropomyosin is moved into the groove between the actin filaments, exposing active sites on actin.
4. Myosin heads bind to active sites on actin molecules.
5. ATP is hydrolyzed.
6. Myosin heads pull on the thin filaments (working stroke) and slide them toward the center of the sarcomere.
7. ADP and Pi are released from the thick filament.
8. ATP binds to the thick filament.
9. Myosin heads return to their high-energy shape, ready for the next working stroke.
10. Cycling continues until calcium ions are sequestered by the SR.
11. Myosin cross bridges detach from actin.
So, the correct order of the statements is:
4, 1, 2, 3, 9, 11, 7, 5, 6, 8, 10.