Final answer:
Myosin-I is a motor protein present in all types of cells and is involved in various cellular functions. The body contains three types of muscle tissue: skeletal, smooth, and cardiac, each with distinct features and roles in the body. Muscle cells, or myocytes, originate from mesodermal embryonic cells.
Step-by-step explanation:
Myosin-I is a protein that is involved in cellular movement and can be found in many types of cells, not limited to just muscle cells. It is a motor protein that moves along actin filaments and is involved in various cellular functions, including endocytosis and organelle transport. Thus, the correct answer to the question, "Myosin-I is present in:" is D. all types of cells.
The body contains three types of muscle tissue: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle is voluntary and characterized by long, cylindrical, multinucleate cells. Cardiac muscle cells are found only in the heart, are branch and striated, usually have a single central nucleus, and possess unique features such as gap junctions and the ability to contract autonomously. Smooth muscle is involuntary, with cells that are spindle-shaped and have a single nucleus without visible striations.
Regarding myocyte development, the myocytes, which are the cells of muscles, develop from mesodermal cells in the embryo and differentiate into the specific muscle types. Connective tissue sheaths cover or line muscle tissues, providing structure and support, but only muscle cells themselves have the contractile ability.