Question

Myoglobin is present in
A. all muscle fibers
B. white muscle fibers
C. red muscle fibers
D. none of these

Answer 1

Hint: Muscles present in all higher vertebrates are used for a variety of purposes like locomotion, changing postures and producing force. It is a soft tissue capable of contraction and relaxation. The muscle cells contain two types of protein that work together to produce contraction and then relaxation of the muscles. Muscles can be smooth or involuntary and skeletal or voluntary in nature.

Complete answer:
Muscles are found in almost all higher vertebrates and are made up of soft tissues that contain protein filaments. A muscle is a collection of muscle tissues that work together to contract and produce a force. The muscle is influenced by the nerve impulse which is sent by the nervous system. This causes the protein present in the muscle cells to work to generate force which brings about movement.

The muscle contains two filaments namely actin and myosin which works by producing a contraction that causes change in the shape and length of the muscles. Myosin filaments work together by binding with actin to generate muscle contraction. The action of the myosin filaments is dependent on the presence and hydrolysis of the energy providing ATP molecules.

Skeletal muscle or voluntary muscles are associated with the skeletal movements and are required for movement and changing postures. The skeletal muscle fibres are important for various physiological and morphological properties. They can be fast twitch, slow twitch and intermediate twitch. The red muscles or the slow twitch is denser with capillaries and contain more myoglobin and mitochondria. The fast twitch or the white muscles are less dense with lesser mitochondria and myoglobins. The red muscle fibres have much better capillary supply with greater number of mitochondria. It is responsible for ATP supply to the muscle cell, therefore they are specialized for sustained work. But white muscle cells have less capillary, fewer mitochondria, so they do not have such good supply as the red cells.
The myoglobins present in the muscle cells allow the organism to work in absence of oxygen supply as in the diving mammals such as whales. The whales are able to breath for a significant time due to the presence of myoglobins in the muscle cells. The presence of myoglobins gives a red colour to the muscle which is due to the presence of heme pigments.

Therefore, the correct option is option C.

Note:
Red muscle fibres have a large number of mitochondria and are darker in colour due to the presence of myoglobin whereas, the white muscle fibres have low number of mitochondria and myoglobin. Thus, red muscle fibres are highly resistant to fatigue. Red muscles are skeletal muscles that are rich in capillaries, myoglobin, and mitochondria while white muscles have a smaller number of capillaries, myoglobin, and mitochondria. Myoglobin imparts a red colour to the red muscle fibres due to its pigments that are bear iron and oxygen binding capability.