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MBBS Biochemistry — practice by topic

Browse 3 questions across 1 Biochemistry topics. Choose what you want to revise, then open a question to check its answer and worked solution.

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Biochemistry topics

Muscle Tissue (3)

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Which ATP source powers only the first approximately 15 seconds of a muscle contraction before another source must take over?Read the answer and worked solution →Roughly what percentage of the ATP required by a resting or moderately active muscle is supplied by aerobic respiration?Read the answer and worked solution →

Worked practice questions

Which ATP source powers only the first approximately 15 seconds of a muscle contraction before another source must take over?

  1. Stored ATP alone
  2. Aerobic respiration
  3. Creatine phosphate
  4. Anaerobic glycolysis
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Correct answer: C. Creatine phosphate

1. Because stored ATP in muscle lasts only a few seconds, muscle relies on a sequence of regeneration mechanisms. 2. Creatine phosphate transfers its phosphate to ADP very quickly via creatine kinase, powering the first few seconds of contraction. 3. However, creatine phosphate stores can only sustain about 15 seconds of activity. 4. Anaerobic glycolysis and aerobic respiration are the slower sources that take over afterward, and stored ATP alone lasts only a few seconds, all shorter or different from the 15-second creatine phosphate window. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 10 "Muscle Tissue", section 10.3, p. 419_

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Roughly what percentage of the ATP required by a resting or moderately active muscle is supplied by aerobic respiration?

  1. 50 percent
  2. 15 percent
  3. 36 percent
  4. 95 percent
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Correct answer: D. 95 percent

1. Aerobic respiration breaks down glucose or other nutrients with oxygen to produce carbon dioxide, water, and ATP in the mitochondria. 2. Because it is far more efficient per glucose molecule than glycolysis, it dominates ATP supply at rest. 3. Approximately 95 percent of the ATP required for resting or moderately active muscle comes from aerobic respiration. 4. 36 ATP per glucose is aerobic respiration's yield per molecule, a different figure from its percentage share of total ATP supply. 5. 50 percent understates how dominant aerobic respiration actually is at rest. 6. 15 percent understates it even further, closer to what anaerobic pathways alone might contribute. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 10 "Muscle Tissue", section 10.3, p. 420_

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