Question

Skeletal muscle fibers differ with respect to energy metabolism. Relatedly, which one of the following characteristics distinguishes a Type I fiber from a Type II fiber?

a) Color
b) Contraction speed
c) Fatigue resistance
d) Fiber diameter

Answer 1

c) Fatigue resistance

One of the key characteristics that distinguish Type I (slow-twitch) muscle fibers from Type II (fast-twitch) muscle fibers is fatigue resistance. Type I fibers are more fatigue-resistant compared to Type II fibers. They are well-suited for sustained, endurance-type activities due to their reliance on oxidative metabolism and a high capacity for aerobic energy production. In contrast, Type II fibers are more associated with rapid, anaerobic contractions and are generally less fatigue-resistant.

Answer 2

The main characteristic that distinguishes a Type I fiber from a Type II fiber is fatigue resistance. Type I slow oxidative fibers can resist fatigue due to their aerobic respiration metabolism, high mitochondria content, and presence of myoglobin.

Step-by-step explanation:

The characteristic that distinguishes a Type I fiber from a Type II fiber is its fatigue resistance. Type I fibers, also known as slow oxidative (SO) fibers, contract relatively slowly and use aerobic respiration (oxygen and glucose) to produce ATP, which allows them to be highly resistant to fatigue. They can sustain aerobic activity for long periods due to their high content of mitochondria and myoglobin. In contrast, Type II fibers consist of fast oxidative (FO) and fast glycolytic (FG) fibers, which have fast contractions and primarily use anaerobic glycolysis, leading to quicker fatigue compared to Type I fibers.

Type I fibers, being high in myoglobin content, also tend to have a red color. This redness is due to the presence of myoglobin that stores oxygen in muscle cells. Their high amounts of mitochondria are the reason these fibers can sustain contractions for extended periods, making them crucial for endurance activities.