Question

Describe three processes that muscle cells use to make ATP when it is needed for muscle contraction. Please include the ATP yield for each process.

Answer 1

The three processes that muscle cells used to produce ATP are vis creatinine phosphate, aerobic respiration and anaerobic respiration.

1) Creatinine phosphate: ADP reacts with creatinine phosphate to form ATP, creatinine and energy. The muscle produces creatinine phosphate when there is excess ATP in muscle during periods of rest. Creatinine phosphate donates a high energy phosphate to ADP. This reaction is catalyzed by creatinine phosphate kinase and provides ATP for first 1-20 sec of muscle contraction. There is production of 1 ATP per creatinine phosphate used.

2) Anerobic respiration: Anerobic respiration occurs in absence of oxygen. Hence, glycolysis will occur but due to lack of oxygen, pyruvate will be converted to lactic acid. There is a net production of only 2 ATP per glucose molecule broken down. Pyruvate is broken down to lactic acid and water. Lactic acid accumulation leads to fatigue in the muscle cells.

3) Aerobic respiration: Glucose is broken down to carbon dioxide and water in aerobic respiration, with release of ATP in presence of oxygen. Aerobic respiration includes glycolysis, Krebs/TCA cycle and electron transport chain. It occurs in mitochondria of muscle cells. Yield of ATP is 32 ATP per glucose (NADH= 2.5ATP and FADH2-= 1.5ATP).