Muscle Metabolism. Goals: Describe three ways in which ATP is regenerated during muscle contraction...

Muscle Metabolism

Muscle MetabolismGoals:Describe three ways in which ATP is regenerated during muscle contraction

Relate the oxygen deficit to causes of muscle fatigue

Muscle Metabolism

Muscle MetabolismThese pathways are:Direct phosphorylation of ADP by creatine phosphate

Anaerobic glycolysisAerobic respiration

Muscle Metabolism Creatine Phosphate

PhosphorylationActive muscles can use all ATP within a few twitches.

Creatine Phosphate is a high energy storage molecule

The transfer of its high energy phosphate to ADP can provide up to 16 seconds of ATP in a muscle.

Creatine phosphate is regenerated during rest.Its money for health food companies.

Muscle Metabolism Creatine Phosphate

Phosphorylation

This pathway is used for very quick bursts of muscle activity, such as sprinting.

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Figure 9.19a Pathways for regenerating ATP during muscle activity.

Coupled reaction of creatinephosphate (CP) and ADP

Energy source: CP

(a) Direct phosphorylation

Oxygen use: NoneProducts: 1 ATP per CP, creatine

Duration of energy provision:15 seconds

Creatinekinase

ADPCP

Creatine ATP

Muscle MetabolismGlycolysis and Lactic Acid Formation

This pathway generates ATP after the Creatine phosphate system is exhausted.

Actively contracting muscles compress arteries, reducing blood flow and oxygen.

This produces anaerobic conditions which produce lactic acid.

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Figure 9.19b Pathways for regenerating ATP during muscle activity.

Energy source: glucose

Glycolysis and lactic acid formation

(b) Anaerobic pathway

Oxygen use: NoneProducts: 2 ATP per glucose, lactic acidDuration of energy provision:60 seconds, or slightly more

Glucose (fromglycogen breakdown ordelivered from blood)

Glycolysisin cytosol

Pyruvic acid

Releasedto blood

net gain

2

Lactic acid

O2

O2ATP

Muscle MetabolismGlycolysis and Lactic Acid Formation

This pathway only produces about 5% as much ATP as aerobic respiration but does it twice as fast.

This pathway extends the ATP supply up to 1 minute of vigorous activity.

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Figure 9.20 Comparison of energy sources used during short-duration exercise and prolonged-duration exercise(1 of 2).

Short-duration exercise

ATP stored inmuscles isused first.

ATP is formedfrom creatinephosphateand ADP.

Glycogen stored in muscles is brokendown to glucose, which is oxidized togenerate ATP.

Muscle MetabolismGlycolysis and Lactic Acid FormationThe Big Lie by State Ed Department

The build up of lactic acid leads does NOT lead to muscle soreness following exercise.

It coincides with muscle fatigue.

Muscle MetabolismMuscle Fatigue

Muscle fatigue is the inability to contract even in the presence of stimuli.

Muscle MetabolismMuscle Fatigue

Muscle fatigue is the inability to contract even in the presence of stimuli.

It is NOT due to a lack of ATP. This would lead to contractures. This is seen with writers cramp.

Muscle MetabolismMuscle Fatigue

Ionic disturbances are the most likely cause of muscle fatigue: Potassium ion lost from the muscle cells

Interference of Calcium regulation

Muscle MetabolismAerobic Respiration

This pathway produces 95% of the ATP. This pathway occurs in the mitochondria and requires oxygen.

Muscle MetabolismAerobic Respiration

Muscle MetabolismAerobic Respiration

Muscle glycogen provides the major source of glucose followed by blood glucose and then fats.

It provides the most ATP but is slower because of all the enzymatic steps.

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Figure 9.19c Pathways for regenerating ATP during muscle activity.

Energy source: glucose; pyruvic acid;free fatty acids from adipose tissue;amino acids from protein catabolism

(c) Aerobic pathway

Aerobic cellular respiration

Oxygen use: RequiredProducts: 32 ATP per glucose, CO2, H2ODuration of energy provision: Hours

Glucose (fromglycogen breakdown ordelivered from blood)

32

O2

O2

H2OCO2

Pyruvic acidFattyacids

Aminoacids

Aerobic respirationin mitochondriaAerobic respirationin mitochondria

ATP

net gain perglucose

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Figure 9.20 Comparison of energy sources used during short-duration exercise and prolonged-duration exercise (2 of 2).

Prolonged-duration exercise

ATP is generated by breakdown of severalnutrient energy fuels by aerobic pathway.This pathway uses oxygen released frommyoglobin or delivered in the blood byhemoglobin. When it ends, the oxygendeficit is paid back.

Muscle MetabolismAerobic Respiration

This pathway is used for long periods of exercise such as cross county and marathon events.

Muscle MetabolismComparisons

Muscle Fiber TypeDeep down we are all turkeys

Muscle Fiber TypeDeep down we are all turkeys

Remember white meat/ dark

meat?

Muscle Fiber TypeMuscle fibers are divided into two types based on their metabolism.1.Slow oxidative fibers (Red Meat)

Aerobic Myoglobin present (Red Color) Large number of mitochondria Low glycogen content Slow rate of fatigue Good for endurance activities

Muscle Fiber TypeMuscle fibers are divided into two types based on their metabolism.

2. Fast Glycolytic FibersAnaerobicMyoglobin content is low (White Color)Glycogen content is highFatigues quicklyFew mitochondriaShort term intense movements

Muscle Fiber Type A third muscle type, the Fast Oxidative Fiber has characteristics of both muscle types. These muscle can convert to the other types based on training.

Adaptation to Exercise Endurance exercising will:Increase the number of capillaries surrounding the muscle fibers (why)Increase the number of mitochondria (why)May convert some of the fast glycolytic fibers to fast oxidative fibers Increase the efficiency of the heart (why)

Adaptation to Exercise Resistance exercising will:Increase the increase the size of the muscle fibersIncrease the amount of connective tissue between the fibersMay convert some of the to fast oxidative fibers to fast glycolytic fibers

Adaptation to Exercise

Adaptation to Exercise Large bulky muscles are due to the increase size of individual muscle fibers (fast glycolytic fibers)

Adaptation to ExerciseWho has the larger heart?