Background: (use this information to help you answer questions 10-24)
Under normal conditions muscles utilize oxygen (aerobic respiration) to make ATP from glucose. This process is very efficient and produces 38 ATPs for each molecule of glucose. Carbon dioxide and water are the by-products of this reaction. When muscles undergo rigorous exercise they require more oxygen to make ATP than the blood can supply (sprinting). At this point the muscle is forced to produce ATP without oxygen (anaerobic respiration).
Anaerobic respiration produces only 2 ATPs for each molecule of glucose. The product of this reaction is lactic acid. The advantages of anaerobic respiration are that the muscle cell can make ATP without oxygen and it can make ATP very quickly. This is a particular advantage when lifting heavy objects. The big disadvantage to anaerobic respiration is that it produces lactic acid which gives muscles a temporary burning sensation. Muscle fatigue results when the demand for ATP is greater than the rate at which ATP can be produced in the muscle fibers. As a consequence, ATP levels are too low for muscle fibers to produce their maximum force contraction. Under condition of extreme fatigue, muscles become incapable of contracting or relaxing.
In the lab you experienced the use of aerobic respiration and anaerobic respiration by the muscle fibers in your fingers/arms. You experienced the production of lactic acid and the sensation it produces in you muscles. The lab demonstrated how your body used the resources available to provide you with the energy you need to do work.
