Animal Muscles

Stimulus atp is needed to break the myosin actin

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Unformatted text preview: ntraction depends on ATP supply. Stimulus! ATP is needed to break the myosin-actin bonds, and “re-cock” the myosin heads. To maintain contraction, actin–myosin bonds have to keep cycling. Stimulus! ! Sources of ATP Muscle cells have three sources of ATP Muscles have three systems for obtaining ATP: Creatine-P ! Glycogen, glucose or fatty acids Glycogen ! ! • Immediate system uses preformed ATP and creatine-phosphate Glycolysis (anaerobic) ! Oxidative phosphorylation (aerobic) ! • Glycolytic system metabolizes carbohydrates to lactic acid and pyruvate ATP ! • Oxidative system metabolizes carbohydrates and fatty acids to H2O and CO2 ! muscle contraction ! Supplying Fuel for High Performance Sources of ATP ATP/CP ! ! Oxidative system Glycolysis ! ! Immediate System: •  Muscles contain creatine phosphate (CP) which stores energy in a phosphate bond that can transfer to ADP •  Immediate system = ATP + CP. This system is exhausted within seconds. ! Creatine phosphate as an “immediate buffer” for ATP Asafa Powell (Jamaica) 100 m world record: 9.74 seconds! Creatine! Creatinephosphate! Creatine kinase ! ADP ! ATP ! Sources of ATP Sources of ATP ! The glycolytic system ! Oxidative phosphorylation: •  Enzymes are in the cytoplasm (sarcoplasm). •  ATP generated is directly available to myosin (fast). •  Produces large amounts of ATP. •  Anaerobic. •  Aerobic. •  Not very efficient (low ATP yield). •  Occurs in mitochondria. •  Lactic acid accumulates. •  ATP must diffuse from mitochondria to the •  Immediate and glycolytic systems provide energy for less than one minute. myosin in the cytoplasm (slower than other two systems). ! ! What Determines Muscle Strength and Endurance? What Determines Muscle Strength and Endurance? ! Slow-twitch muscle fibers: There are two main types of skeletal muscle fibers:...
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