UWorld MCAT Biology Test

What concept refers to the amount oxygen necessary to bring the muscle back to its resting? Hint: It's equivalent to the difference b/n the amount of oxygen actually required for physical activity and the total amount of oxygen used - Answer - Oxygen debt or Excess post-exercise oxygen consumption (EPOC) What do muscles need to contract? - Answer - ATP What is the primary source of ATP in muscle fibers during vigorous, long-term exercise? - Answer - Aerobic respiration - generates more molecules per metabolized molecule than anaerobic glycolysis What are the 4 ways in which muscle fibers compensate when 1. oxygen delivery from the blood becomes insufficient (e.g., rapid, high-intensity exercise) and 2. demand for contraction EXCEEDS the speed at which aerobic respiration can generate ATP? - Answer - 1. Utilize ATP stored in muscle fiber 2. Break down creatinine phosphate, a high energy molecule stored by muscle cells during periods of rest, to generate ATP 3. Generate ATP via anaerobic glycolysis: yields 2 pyruvate & 2 net ATP per glucose molecule; absence of oxygen leads to 2 pyruvate converted to lactic acid 4. Continue aerobic respiration using oxygen bound to myoglobin (red-pigmented oxygen storage molecule) True/False: s/p motor neuron input ceases, muscle fiber relaxes and begins replenishing their back up energy reserves to prepare for the next burst of activity and consequently, oxygen intake (deep breathing) remains elevated even after physical activity has stopped since oxygen is needed to resynthesize ATP and creatine phosphate? - Answer - True What happens to calcium during rest/relaxation? - Answer - Sequestered into sarcoplasmic reticulum T/F: Internal skeletons (like those in humans) are called endoskeletons? - Answer - True T/F: External skeletons (like those in arthropods) are called exoskeletons? - Answer - True