Question

multiple choice question

which are long protein cords found in sarcoplasm of skeletal muscle cells?

glycogen
myofibrils
myoglobin

Explanation:

Analyze the question stem

The question asks to identify the long protein cords found in the sarcoplasm of skeletal muscle cells. Sarcoplasm is the cytoplasm of a muscle fiber, which contains specialized organelles and structures.

Evaluate the first option: Glycogen

Glycogen is a complex carbohydrate (polysaccharide) used for energy storage in animal cells, particularly in liver and muscle tissues. It is not a protein cord.

Evaluate the second option: Myofibrils

Myofibrils are long, cylindrical, thread-like organelles that run parallel to the length of the muscle fiber. They are composed of bundles of myofilaments (actin and myosin proteins) and are the contractile elements of skeletal muscle cells.

Evaluate the third option: Myoglobin

Myoglobin is a red, iron- and oxygen-binding protein found in the sarcoplasm of muscle fibers. It is a globular protein, not a long protein cord, and functions to store oxygen for use during muscle contraction.

Formulate the final conclusion

Based on the structural definitions, myofibrils are the long protein cords that occupy most of the sarcoplasm in skeletal muscle cells.

Answer:

• Glycogen
• Myofibrils (Correct answer)
• Myoglobin