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 groupGlucose 2 pyruvic acid + 2 ATP

pyruvic acid (each = 17 ATP)

CO2+H2O + 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

Glucose 2 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 O2)

Total ATP=2

Muscle Fatigue Normal muscle function requires 1) ATP in reserve 2) normal blood flow 3) normal blood O2 concentration

during strenuous exercise....muscles are forced to use anaerobic respiration because the muscle can no longer contract

Leads to O2 debt=extra O2 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 O2 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.