What are the two parts of meromyosin?

The two parts of meromyosin are heavy meromyosin (HMM) and light meromyosin (LMM).

Meromyosin is a segment of the myosin molecule, which is a protein responsible for muscle contraction. Myosin consists of two main parts: the head and the tail. When myosin is broken down enzymatically, it splits into two fragments called heavy meromyosin and light meromyosin.

Heavy meromyosin contains the head and neck region, which binds to actin filaments and has ATPase activity essential for muscle contraction. The light meromyosin forms the long tail part of the molecule and helps in filament assembly and structural stability. Together, these two parts play a crucial role in the sliding filament theory of muscle contraction, where myosin heads pull actin filaments to shorten muscle fibers.

Understanding meromyosin's structure helps explain how muscles work at a molecular level and how energy is used to produce movement.