Imagine that a researcher has dissected out a single muscle bundle from a triceps muscle biopsy. She sections this bundle and stains it for a variety of muscle-associated proteins. After staining, when the researcher zooms in on a sarcomere, she notices that a certain protein always dots the periphery along the length of the thin filaments. This protein is most likely:

Explanation:

This protein is most likely:  Tropomyosin.

Sacromere is the structural unit of myofibrils i.e. the fibres of the muscles.

Tropomyosin is the muscle protein that function in contraction of muscle filaments.They are arranged laterally along the myofilament. When the researcher is observing the sacromere, she is observing the muscle fibre.  So, the protein that lines the periphery along the thin filament is more likely to be tropomysin.

when a reversible reaction is occurring in both directions at the same rate; the products and reactants do not change in concentration. a chemical reaction where the compound is broken into its constituent parts.