Which pigment stores oxygen in muscle and is more abundant in slow-twitch fibres?

• A. Haemoglobin
• B. Myoglobin
• C. Oxyhaemoglobin Dissociation
• D. pH

Answer: (B)

Oxygen storage in muscle is provided by myoglobin, a pigment found inside muscle fibres that binds and holds oxygen close to the mitochondria. Slow-twitch fibres rely heavily on oxidative metabolism for endurance, so they contain more mitochondria and more myoglobin, giving them a greater capacity to store and deliver oxygen during prolonged activity. This internal oxygen reservoir helps sustain aerobic respiration when blood oxygen levels drop during exercise. Haemoglobin, by contrast, is the oxygen-carrying pigment in blood, not in muscle, and the term oxyhaemoglobin dissociation refers to the oxygen release from haemoglobin, not storage in muscle. pH relates to how readily oxygen is released systemically, but it isn’t a pigment. Thus, the pigment that stores oxygen in muscle and is more abundant in slow-twitch fibres is myoglobin.