Final answer:
The myofibril is made up of myosin protein molecules surrounding a strand of elastic protein called titin. It consists of actin and myosin filaments that overlap each other.
Step-by-step explanation:
The structure that is made up of about 300 myosin protein molecules surrounding a strand of elastic protein called titin is the myofibril.
Each myofibril is composed of two types of protein filaments: actin filaments and myosin filaments. Actin filaments are thinner, while myosin filaments are thicker. Within a myofibril, the myosin filaments overlap the actin filaments.