Question

question 23 (1 point)
listen
the contractile organelles of a skeletal muscle fiber are thread - like structure called:
z discs.
myoglobin.
myofibrils.
m lines.

Explanation:

• Z - discs: These are the boundaries of a sarcomere (the functional unit of a muscle fiber) but not the contractile organelles.
• Myoglobin: It is an oxygen - binding protein in muscle cells, not a contractile organelle.
• Myofibrils: These are the thread - like contractile organelles in a skeletal muscle fiber. They are made up of sarcomeres which contain the contractile proteins actin and myosin.
• M - lines: These are the structures in the middle of a sarcomere that hold thick filaments (myosin) in place, not the contractile organelles.

Answer:

myofibrils.