Muscle & Energy

Intro A single muscle fiber contains 15 billion thick filaments During active contraction, 2500 ATP molecules are used-PER SECOND!! muscles require energy (ATP) to form cross-bridges and move myofilaments together ATP is from breakdown of glucose (cell respiration)

Aerobic Respiration (Kreb’s cycle) ( with oxygen) During contraction, each myosin cross-bridge breaks down ATP, producing ADP + a phosphate group Glucose2 pyruvic acid + 2 ATP pyruvic acid (each = 17 ATP) CO 2 +H 2 O + energy (36ATP) Total ATP = 36

Anaerobic Respiration Glyolysis is the breakdown of glucose to pyruvic acid It is an anaerobic process because it does not require any oxygen Provides a net gain of 2ATP + 2 pyruvic acid molecules Glucose2 pyruvic acid + 2ATP

Lactic Acid build up Occurs when glycolysis produces pyruvic aicd faster than it can be used by mitochondria Pyruvic acid then gets converted to lactic acid (causes soreness and later needs to be broken down with O 2 ) Total ATP=2

Muscle Fatigue Normal muscle function requires 1) ATP in reserve 2) normal blood flow 3) normal blood O 2 concentration during strenuous exercise....muscles are forced to use anaerobic respiration because the muscle can no longer contract Leads to O 2 debt=extra O 2 needs to be taken in to convert lactic acid back to Pyruvic acid then aerobic respiration. takes over (Kreb’s cycle) This restores balance of O 2 in blood, lungs, and other body fluids

Resting muscle: Fatty acids are broken down; the ATP produced is used to build energy reserves of ATP

Moderate activity: Glucose & fatty acids are broken down; the ATP produced is used to power muscle contraction

Peak activity: Most ATP is produced through glycolysis, with lactic acid as a byproduct. Mitochondria only provides 1/3 of the ATP used.