Please check my answer.
What us the basic unit of a muscle?
A. Myosin
B. Actin
C. Muscle fibers
D. Myofibrils
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I think it's either C or D.
To identify the correct answer to the question "What is the basic unit of a muscle?" let's break down the options provided:
A. Myosin: Myosin is a contractile protein present in muscle cells but it is not the basic unit of a muscle. Therefore, we can eliminate this option.
B. Actin: Actin is another contractile protein that is found in muscles, but, similar to myosin, it is not the basic unit of a muscle. So, we can eliminate this option as well.
C. Muscle fibers: Muscle fibers are the individual cells that combine to form a muscle, and they are composed of myofibrils. So, each muscle fiber is made up of multiple myofibrils. This indicates that muscle fibers are not the basic unit of a muscle, but rather a component of it. Therefore, we can eliminate this option.
D. Myofibrils: Myofibrils are the actual basic units of muscles. They are thread-like structures found inside muscle fibers that are responsible for contraction. They contain the contractile proteins myosin and actin, among others. Each myofibril is made up of repeating units called sarcomeres, which are responsible for muscle contraction.
Based on this information, the correct answer is D. Myofibrils.
Remember, when trying to answer a question like this, it is advisable to have a basic understanding of the topic. In this case, knowing the structural organization of muscle tissue would have helped in identifying the correct answer.