Question

A student was given a sample of two muscles marked as 1 and 2. When he compared the muscles he found that muscle 1 contains large amounts of myoglobin and utilises large amounts of stored oxygen for ATP production whereas muscle 2 contains few myoglobin, mitochondria and high sarcoplasmic reticulum. Identify the correct statement regarding muscles 1 and 2 from the option given below.
A. Both muscles are called aerobic muscles.
B. Both muscles are called red fibres and depend on the aerobic process for energy.
C. Muscle 1 is called white fibres and whereas muscle 2 depends on the aerobic process for energy.
D. Muscle 1 is called red fibres and aerobic muscles whereas muscle 2 is called white fibres and depends on the anaerobic process for energy.

Answer 1

Hint:
On the basis of intensity, speed of contraction, colour of fibres from which the muscles are made, and the substrates or fuel used to provide energy, muscles are divided into two main categories: white muscle fibre and red muscle fibre.

Complete answer:
Type 1 or red muscle fibres are also called slow twitch muscles due to the time taken for contraction by them. It is rich in myoglobin which offers a red tinge to it. Structurally, it is packed with capillaries, mitochondria and myoglobin. It also carries oxygen. To provide energy, it depends on the catalysis of fats and carbohydrates. Although the force exerted by them is little compared to white muscle fibres.
Type 2 or white muscle fibres provide intense energy for contraction. These are also known as fast twitch fibres as they constitute fibres that perform quick contraction. Unlike red muscle fibres, they have much less composition of myoglobin and mitochondria. Though their contraction is powerful their period of contraction is less because they get fatigued soon. Thus, they have to rely on anaerobic processes.
Thus, the correct answer is: Muscle 1 is called red fibres and aerobic muscles whereas muscle 2 is called white fibres and depends on the anaerobic process for energy.

Option ‘D’ is correct

Note:
White muscle fibres also help in connecting different structures of the body. These are found in the muscles of the eyeball and upper limbs. These are large in diameter, unlike red muscle fibres. Red muscle fibres are found in the abdomen, pelvis, back, extensors of the leg et cetera.