Myoglobin
O produces the end plate potential.
is a protein involved in the direct phosphorylation of ADP.
o holds a reserve supply of oxygen in muscle cells.
O breaks down glycogen.

holds a reserve supply of oxygen in muscle cells.

Explanation:

Myoglobin is an iron-containing protein whic is found in the muscle cells. It is similar to hemoglobin with respect to its structure. The main function of myoglobin is to store oxygen in the muscle cells that is need for muscles functioning. Myoglobin receives oxygen from the red blood cells and transports it to the mitochondria of muscle cells, where the oxygen is used in cellular respiration to produce energy. The organism can utilize the oxygen in its lungs for a much longer period of time if the concentration of myoglobin becomes high in the muscle cells,

Myoglobin, a molecule similar to hemoglobin, holds a reserve supply of oxygen in muscle cells (third option).

Explanation:

Myoglobin is a protein found predominantly in skeletal or heart muscle fiber, with a chemical structure that, like hemoglobin, contains a heme prostetic group with iron atoms, capable of fixing oxygen.

For this reason, it is a molecule that allows the muscle to have an oxygen reserve, necessary to meet the demand during movement and physical exercise.

Myoglobin has a red color, depending on its heme group. Each iron element of the heme is found in the middle of the protoporphyrin ring, and its ferrous oxidation state Fe²⁺ or ferric Fe⁺³ is the characteristic that allows it to fix or yield oxygen.

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