The unit of contraction within skeletal muscle cells is called the sarcomere. A sarcomere contracts when the

Question:

The unit of contraction within skeletal muscle cells is called the sarcomere. A sarcomere contracts when the filamentous protein myosin stretches into a high-energy conformation and binds to the filamentous protein actin. When the myosin returns to its low-energy, relaxed conformation, actin is pulled, and the sarcomere contracts. The following steps relate ATP to each step of this process.
1- Myosin binds to actin (ADP is attached).
2- Myosin returns to low-energy conformation (ADP is released).
3- Myosin releases actin (ATP binds).
4- Myosin stretches to high-energy conformation (ATP is hydrolyzed).

A calcium ion is required for the binding of myosin to actin. If a calcium chelator, such as EDTA, is added to a muscle cell, which of the following graphs shows how it will affect muscle contraction? (A) Percent of Myosin Confirmations of Myosin vs. nM of EDTA 60 40 20 0 0 10 100 Actin-Myosin (high-energy) (B) Percent of Myosin Confirmations of Myosin vs. nM of EDTA 100 50 0 0 10 H L 100 1000 Actin-Myosin (C) Percent of Myosin Confirmations of Myosin vs. nM of EDTA 100 50 0 0 10 1| + 1000 100 Actin-Myosin (D) Percent of Myosin Confirmations of Myosin vs. nM of EDTA 100 50 0 0 10 J H 100 Actin-Myosin (high-energy)