Energy Sources for Muscle Contractions

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Energy Sources for Muscle Contractions
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ATP in Muscle Contractions

• Cross bridge movement
• Detachment of myosin heads
• Active transport of calcium into SR.

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ATP

• Main useable source of energy for cells.
• Sources of energy (ex.food) must be changed into
  ATP to be useful.
• ATP adenine triphophate- fully charged
• ADP- adenine diphosphate- half charged.
• ADP P ? ATP

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Sources of Energy (phosphate) to refuel ATP

• Stored ATP in muscle cells - 4-6 sec.
• Stored Creatine phosphate- 10 sec.
• Stored glycogen via anaerobic respiration- 30-60
  sec.
• Sprinter
• Aerobic respiration- hours
• Triathlete

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Creatine phosphate (CP)

• Stored in skeletal muscle
• Storage pool of CP is 5-10 X more than ATP
• Benefit- produces ATP quick (fast chemical
  reaction)
• How is it a source of E?
• 1CP ADP ? 1ATP C

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Glycogen (stored form of glucose)

• Anaerobic respiration (lactic acid fermentation)-
  Chemical reaction in sarcoplasm
• Glucose (from glycogen breakdown or glucose in
  blood)
• ? ? 2 ATP produced
• Lactic acid
• Benefit- produces ATP quick
• Negatives
• lots of glucose is used for small amounts of ATP.
• Lactic acid fatigue- oxygen debt-liver requires
  oxygen to get rid of lactic acid

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Oxygen Transport

• Hemoglobin protein in red blood cells that
  binds to O2 for transport
• Myoglobin protein in muscle fibers that binds
  to O2 for temporary storage

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Aerobic respiration

• 95 ATP is produced using this process.
• Benefit
• 38 ATPs produced per glucose
• Food sources are plentiful muscle glycogen,
  glucose, fatty acids from adipose tissue, amino
  acids from protein
• Negative
• Requires continuous oxygen nutrients
• Loses about 60 of energy as heat
• SLOW chemical reaction
• Do you remember the chemical reaction?

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Aerobic Respiration

• Reactants?
• Glucose- C6H12O6 (food absorbed into blood by
  small intestine)
• Oxygen- O2 (air absorbed into blood by lungs)
• What are the products?
• Carbon dioxide- CO2
• Water- H2O
• Energy- ATP
• Where in a cell does it occur?
• Mitochondria

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Muscle Fatigue

• Inability to contract even if muscle is being
  stimulated
• Lack of blood supply (glucose oxygen)
• Lack of acetylcholine
• Lack of ATP
• Ex. Writers cramp- continuous contraction
  because cross bridges cant detach
• Rigor mortis- stiffness after death (48 hours)
• Accumulation of lactic acid

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Effect of exercise on Muscles

• Endurance (Aerobic) exercise- running
• Increases capillaries around muscle fibers
• Increases of mitochondria
• Increases myoglobin
• Resistance (Anaerobic) exercise-weights
• Increase size of muscle fiber
• Increase mitochondria
• Increase myofilaments (sarcomeres)
• Increase connective tissues