section 4, chapter 9: energy for muscles

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

New ATP molecules are synthesized by 1. Hydrolysis of Creatine Phosphate2. Glycolysis (anaerobic respiration)3. Aerobic Respiration

The energy from creatine phosphate hydrolysis cannot be used to directly power muscles. Instead, it’s used to produce new ATP.

Creatine Phosphate

Creatine Phosphate can be hydrolyzed into Creatine, releasing energy that is used to make new ATP.

Creatine Phosphate…continued

When cellular ATP is abundant, creatine phosphate can be replenished by phosphorylating creatine.

Creatine Phosphate provides energy for only about 10 seconds of a high intensity muscle contraction.

Glycolysis

Anaerobic respiration (glycolysis) occurs in the cytosol of the cell and does not require oxygen.

Glucose molecules are partially broken down producing just 2 ATP for each glucose.

If there isn’t sufficient oxygen available, glycolysis produces lactic acid as a byproduct.

Oxygen debt of glycolysisExercise and strenuous activity depends on anaerobic respiration for ATP supplies.

Oxygen debt is the amount of oxygen needed by liver cells to convert accumulated lactic acid back to glucose.

During exercise anaerobic respiration causes lactic acid to accumulate in the cells.

After exercise, when oxygen is available the O2 is used to convert lactic acid back to glucose in the liver.

Oxygen debt

Aerobic respiration (uses oxygen) occurs in the mitochondria and it includes the citric acid cycle & electron transport chain.

Aerobic respiration is a slower reaction than glycolysis, but it produces the most ATP.

MyoglobinOxygen binding protein (similar to hemoglobin) within

muscles-Provides additional oxygen supply to muscles

Aerobic Respiration

Aerobic RespirationAerobic respiration is used primarily at rest or during light exercise.

Muscles that rely on aerobic respiration have plenty of mitochondria and a good blood supply.

Energy Sources for ContractionFigure 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.

Muscle Fatigue

• Muscle Fatigue = Inability for the muscle to contract

• Several factors can cause muscle fatigue:• Decreased blood flow• Ion imbalances across the sarcolemma• Lactic acid accumulation – (greatest cause of fatigue)

• Cramp: • A cramp is a sustained, involuntary, and painful muscle

contraction• It’s due to electrolyte imbalance surrounding muscle

Heat Production• Heat is produced as a 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