Chapter 9, Section 4
Energy Sources for Contraction
Energy Sources for Contraction
ATP provides the energy to power the interaction between actin & myosin filaments. • However, ATP is quickly spent and must be replenished
ATP is replenished by 1. Creatine Phosphate 2. Glycolysis (anaerobic respiration) 3. Aerobic Respiration
Energy Sources for Contraction 1. Creatine phosphate • stores energy that quickly converts ADP to ATP • when ATP runs low, Creatine phosphate is hydrolyzed into Creatine (similar to ATP hydrolysis). - releases energy for ATP synthesis
Creatine Phosphate cannot directly power muscles. It only produces new ATP.
Creatine Phosphate…continued • When ATP is abundant, Creatine can be reformed into Creatine Phosphate using energy from ATP. • Creatine Phosphate provides energy for only about 10 seconds of a high intensity muscle contraction.
Oxygen Supply and Cellular Respiration • Anaerobic Respiration • Glycolysis – anaerobic respiration • Occurs in cytosol • Partial breakdown of glucose, producing few ATP • Forms lactic acid if oxygen is not available
• Aerobic Respiration • Citric acid cycle & electron transport chain • Occurs within mitochondria • Slower reaction than glycolysis, but produces most ATP •Myoglobin Oxygen binding protein (similar to hemoglobin) within muscles -Provides additional oxygen supply to muscles
Energy Sources for Contraction
Figure 9.13. The oxygen required for aerobic respiration is carried in the blood and stored in myoglobin. In the absence of oxygen, anaerobic respiration uses pyruvic acid to produce lactic acid.
Oxygen Debt Aerobic respiration is sufficient for a person at rest, or moderately active. - However, oxygen supplies are not sufficient for more strenuous activity. High energy exercise depends more on glycolysis for ATP.
Oxygen Debt
Glycolysis and Oxygen Debt • Pyruvic acid from glycolysis is converted to lactic acid •Lactic acid accumulates in blood. • Oxygen is required to convert lactic acid back to glucose in the liver. • Oxygen debt = amount of oxygen needed by liver cells to convert accumulated lactic acid back to glucose.
Muscle Fatigue • Muscle Fatigue = Inability to contract muscle • Causes of muscle fatigue: • Decreased blood flow • Ion imbalances across the sarcolemma • Lactic acid accumulation – (greatest cause of fatigue) • Cramp: • sustained, involuntary, and painful muscle contraction • due to electrolyte imbalance surrounding muscle
Heat Production
• By-product of cellular respiration • Muscle cells are major source of body heat • Blood transports heat throughout body core
End of Chapter 9, Section 4