Q.The muscles attached to the bones are called
a. skeletal muscle
b. cardiac muscle
c. involuntary muscle
d. smooth muscles

Myoglobin, a reddish oxygen-binding pigment closely related to haemoglobin, is present within muscle fibres and stores oxygen for use during muscle contraction.

Myoglobin is a small, single-chain globular protein containing one heme group (similar to haemoglobin's heme units) that reversibly binds oxygen. It is found in the sarcoplasm of skeletal and cardiac muscle fibres, where it takes up oxygen diffusing in from the blood and stores it, releasing it when the muscle's own oxygen demand rises during contraction (especially useful during the initial phase of exercise, before increased blood flow catches up). Myoglobin's high affinity for oxygen at low partial pressures also gives red muscle its characteristic reddish colour.

Myosin, actin and troponin are all contractile/regulatory proteins of the muscle sarcomere involved in the sliding filament mechanism of contraction, not oxygen storage.

Myoglobin is the iron-containing pigment inside muscle fibres that binds and stores oxygen for use during muscle contraction.

Skeletal and cardiac muscle fibres contain myoglobin, a single-chain globular protein closely related in structure to one subunit of haemoglobin, but with a much higher affinity for oxygen. Because of this higher affinity, myoglobin readily takes up oxygen delivered by blood haemoglobin and holds it as a local reserve within the muscle cell (sarcoplasm). During strong or sustained contraction, when the oxygen supplied by blood momentarily falls short of demand, myoglobin releases its stored oxygen to the mitochondria, supporting continued aerobic respiration (ATP production) in the muscle fibre. Muscles that are used for prolonged/aerobic work (red or 'slow' fibres) are richer in myoglobin and appear dark red because of it, while muscles used for short bursts of activity (white or 'fast' fibres) contain less. The other options are unrelated: myosin and actin are the contractile filament proteins that slide over each other to shorten the sarcomere, and troponin is the regulatory protein on the actin filament that controls the exposure of myosin-binding sites in response to calcium.

Oxidative skeletal muscle fibres are called red muscle fibres because their high myoglobin and mitochondrial content (which gives them their red colour) supports sustained aerobic ATP production.

Skeletal muscle fibres are broadly of two physiological types:

• Red fibres (oxidative/Type I): contain abundant myoglobin (which stores and supplies oxygen) and numerous mitochondria, generate ATP mainly through aerobic respiration, contract slowly but resist fatigue — suited for sustained activity like posture-maintaining muscles.
• White fibres (glycolytic/Type II): have less myoglobin, fewer mitochondria, depend mainly on anaerobic glycolysis, contract rapidly and powerfully but fatigue quickly — suited for short bursts of activity.

Since the question specifically asks for the type that uses oxidative metabolism, the answer is the myoglobin-rich, mitochondria-rich red fibres, not the white (glycolytic) ones.