Each myosin molecule of sarcomere is composed of
**Core Concept**
The **sarcomere** is the functional unit of skeletal muscle, and it contains highly ordered arrangements of **actin** and **myosin** filaments. The **myosin** molecule is a key component, responsible for muscle contraction through its interaction with actin. Understanding the structure of myosin is crucial for comprehending muscle physiology.
**Why the Correct Answer is Right**
Each **myosin** molecule is composed of six subunits: two heavy chains and four light chains. The heavy chains consist of a tail region and a head region, with the head region containing the **ATPase** activity necessary for muscle contraction. The light chains are associated with the head region and play a role in regulating **myosin** activity.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the subunit composition of the myosin molecule.
**Option B:** This option is also incorrect as it misrepresents the number and type of subunits in a myosin molecule.
**Option D:** Similarly, this option is incorrect due to its inaccurate description of the myosin molecule's structure.
**Clinical Pearl / High-Yield Fact**
Remember that the interaction between **actin** and **myosin** is fundamental to muscle contraction, and any disruption in this process can lead to muscle weakness or paralysis. Understanding the structure and function of **myosin** is essential for diagnosing and treating muscle disorders.
**Correct Answer:** D. two heavy chains and four light chains