Q: Hundreds of organelles called myofibrils, made up of two types of protein filaments, are contained in each fiber of what?


Read this paragraph and choose the correct option from the provided answers:

Each muscle fiber contains hundreds of organelles called myofibrils . Each myofibril is made up of two types of protein filaments: actin filaments, which are thinner, and myosin filaments, which are thicker. Actin filaments are anchored to structures called Z lines (see Figure below ). The region between two Z lines is called a sarcomere . Within a sarcomere, myosin filaments overlap the actin filaments. The myosin filaments have tiny structures called cross bridges that can attach to actin filaments.

 Choices:

- bone

- hair

- cartilage

- muscle


A:
muscle