Question

Which of the following statements is not a feature of red muscle fibres?
A. They have plenty of mitochondria.
B. They have a high content of myoglobin.
C. They have a high amount of sarcoplasmic reticulum.
D. They are called aerobic muscles.

Answer 1

Hint:
Skeletal muscles are the highly maintained tissues in animals that are voluntary in action. The two main types of muscle fibres in vertebrates are white and red muscle fibres. Red fibres are the slow-twitch, oxidative fibres which are minute in diameter whereas white fibres are fast-twitch fibres and are bigger in diameter.

Complete step by step answer:
Red muscle fibres are the solid extensor muscles which are rich in capillaries. Muscles possess a red-coloured oxygen-storing pigment called myoglobin. The high content of myoglobin gave these fibres their characteristic red appearance. Underneath sarcolemma and between the myofibrils red muscle fibres have many large mitochondria which can utilize large amounts of oxygen stored in them for the purpose of ATP production. Thus, red muscle fibres rely on aerobic glycolysis. Droplets of lipids can be seen in the sarcoplasm of these fibres. Features of red muscle fibres are very efficient in pertaining to the posture or position of the body or overall carriage of the body. Red muscles can contract more often and for a prolonged period of time and are less exposed to fatigue. Less number of developed sarcoplasmic reticulum is present and no accumulation of lactic acid takes place.
Thus, the correct answer is:- They have a high amount of sarcoplasmic reticulum.

Option ‘C’ is correct

Note:
The white muscle fibres are also the skeletal muscles but they possess less amount of myoglobin which makes them appear whitish in appearance. They have fewer mitochondria and large amounts of sarcoplasmic reticulum. These white muscles carry out quick work in a small period of time.