Question

The thick filaments of a muscle fiber are made up of a. actin. b. troponin. c. fascia. d. myosin.

Short answer

The correct answer is d. Myosin, as thick filaments are mainly composed of the protein myosin, while actin and troponin are components of thin filaments and fascia is a connective tissue surrounding muscles.

Step-by-step solution

Understanding muscle fibers and their components

Muscle fibers are composed of many myofibrils, which are in turn made up of two types of protein filaments: thick filaments and thin filaments. These filaments are essential for muscle contraction, and they interact with each other during this process.

Understanding thick filaments

Thick filaments are mainly made up of the protein myosin. Myosin has a rod-like tail and globular heads that can bind to actin, which is the primary component of thin filaments.

Understanding the other options

Let's briefly go through the other options to establish why they are not the correct answer: a. Actin is the main component of thin filaments, not thick filaments. b. Troponin is a protein complex found on thin filaments that regulate muscle contraction by controlling the binding of myosin to actin. c. Fascia is a specialized connective tissue that surrounds and supports muscles, it is not part of thick filaments.

Identifying the correct answer

Given that myosin is the primary component of thick filaments, the correct answer is: d. Myosin