Multiple Choice
Which structure within a skeletal muscle fiber stores calcium ions necessary for muscle contraction?
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9. Muscle Tissue
Introduction to Muscles and Muscle Tissue
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Which characteristic best explains why slow-twitch (type I) skeletal muscle fibers have a high resistance to fatigue?
A
They have low capillary density and rely primarily on anaerobic glycolysis for ATP production.
B
They have a large fiber diameter with low myoglobin content, maximizing rapid force production.
C
They have few mitochondria and store minimal oxygen, but generate ATP mainly from creatine phosphate.
D
They have abundant mitochondria and myoglobin and rely primarily on aerobic (oxidative) metabolism.
Verified step by step guidance1
Step 1: Understand the key characteristics of slow-twitch (type I) muscle fibers. These fibers are specialized for endurance and continuous activity over long periods without fatigue.
Step 2: Recognize that slow-twitch fibers have a high density of mitochondria, which are the organelles responsible for aerobic (oxidative) metabolism, allowing efficient ATP production using oxygen.
Step 3: Note the presence of abundant myoglobin in slow-twitch fibers, which binds oxygen and facilitates its delivery within the muscle cells, supporting sustained aerobic respiration.
Step 4: Contrast this with fast-twitch fibers, which rely more on anaerobic glycolysis and have fewer mitochondria and less myoglobin, making them more prone to fatigue.
Step 5: Conclude that the high resistance to fatigue in slow-twitch fibers is best explained by their abundant mitochondria and myoglobin, enabling them to rely primarily on aerobic metabolism for ATP production.
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