Final answer:
The molecular components of thick filaments in muscle cells are myosin proteins, while thin filaments are primarily made up of actin protein. Troponin and tropomyosin are also present in thin filaments and help regulate muscle contraction.
Step-by-step explanation:
The molecular components of thick filaments in muscle cells are myosin proteins. The tail of a myosin molecule connects with other myosin molecules to form the central region of a thick filament near the M line, while the heads align on either side of the thick filament where the thin filaments overlap.
On the other hand, the primary component of thin filaments is actin protein. Two other components of the thin filament are tropomyosin and troponin. Actin has binding sites for myosin attachment, while tropomyosin prevents actin-myosin interactions when the muscles are at rest and troponin binds to tropomyosin and actin as well as Ca²+ ions to regulate muscle contraction.