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Aerobic & Anaerobic Metabolism in Muscles. Objectives. Recognize the importance of ATP as energy source in skeletal muscle. Understand how skeletal muscles derive and utilize ATP for energy. Differentiate between energy metabolism in red and white muscle fibers. ATP.

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objectives
Objectives

Recognize the importance of ATP as energy source in skeletal muscle.

Understand how skeletal muscles derive and utilize ATP for energy.

Differentiate between energy metabolism in red and white muscle fibers.

slide3

ATP

ATP or adenosine triphosphate is the energy currency used by our body everyday to perform a number of tasks:

  • Maintain body temperature
  • Repair damaged cells
  • Digestion of food
  • Mechanical work – movement
  • ATP↔ ADP +

Energy

slide4
ATPis the most important form of chemical energy stored in cells

Breakdown of ATP into ADP+PO4 releases energy.

Muscles typically store limited amounts of ATP – enough to power 4-6s of activity

So resting muscles must have energy stored in other ways.

ATP

systems of generation of atp
Systems of generation of ATP

The process that facilitates muscular contraction is entirely dependent on body’s ability to provide & rapidly replenish ATP

1- ATP-CreatinePhosphate system

2- Glycolytic system

3- Oxidative system

interaction of energy systems
INTERACTION OF ENERGY SYSTEMS

Immediate

Short-term

Long-term

slide7

Energy Transfer Systems and Exercise

100%

% Capacity of Energy System

Anaerobic Glycolysis

Aerobic Energy System

ATP – Creatine Phosphate

10 sec

30 sec

2 min

5+ min

Exercise Time

energy requirements
Energy requirements

The three energy systems often operate simultaneously during physical activity.

Relative contribution of each system to total energy requirement differs depending on exercise intensity & duration.

Magnitude of energy from anaerobic sources depends on person’s capacity and tolerance for lactic acid accumulation (Athletes are trained so that they will have better tolerance for lactic acid).

As exercise intensity diminishes & duration extends beyond 4 minutes, energy more dependent on aerobic metabolism

aerobic vs anaerobic sources of energy
Aerobic Vs. Anaerobic sources of energy

Aerobic

Requires oxygen

Source of energy:

mainly fatty acids, then carbohydrate

End Products:

CO2, H2O & ATP

  • Anaerobic
    • does not require oxygen
    • Source of energy:
    • ONLY Carbohydrate (anaerobic glycolysis)
    • End Products:
    • Lactate & ATP
muscle fatigue
Fatigued muscle no longer contracts due to:

1- Accumulation of lactic acid (low pH of sarcoplasm)

2- Exhaustion of energy resources ( ADP &  ATP)

3- Ionic imbalance:

Muscle Fatigue
how would a fatigued muscle be able again to contract
How would a fatigued muscle be able again to contract ?

Recovery period: begins immediately after activity ends

Oxygen debt (excess post-exercise oxygen consumption)

i.e. the amount of oxygen required during resting period to restore muscle to normal conditions

muscles and fiber types
Muscles and fiber types

White muscle : (glycolytic)

mostly fast fibers

pale (e.g. chicken breast)

Red muscle: (oxidative)

mostly slow fibers

dark (e.g. chicken legs)

Most human muscles are:

Mixed fibers

pink

slow fibers
Abundant mitochondria

Extensive capillary supply

High concentrations of myoglobin

Can contract for long periods of time

Fatigue resistant

Obtain their ATP mainly from fatty acids oxidation, TCA cycle & ETC (oxidative phosphorylation)

Slow fibers
fast fibers
Large glycogen reserves

Relatively few mitochondria

Produce rapid, powerful contractions of short

duration

Easily fatigued

Obtain their ATP mainly from anaerobic glycolysis

Fast fibers
atp use in the resting muscle cell
ATP use in the resting muscle cell

During periods of muscular rest ATP is required for:

1- Glycogen synthesis (glycogenesis)

i.e. storage form of glucose to be used

during muscular exercise

2- Creatine phosphate production

i.e. energy storage compound to be used at the beginning of muscular contraction

source of atp in resting muscle fibers
Source of ATP in resting muscle fibers

Resting muscle fibers takes up free fatty acids from blood.

Fatty acids are oxidized (in the mitochondria) to produce acetyl CoA& molecules of NADH & FADH2

Acetyl CoA will then enter the citric acid cycle (in the mitochondria)ATP, NADH, FADH2 & CO2

NADH& FADH2will enter the electron transport chain.

 synthesis of ATP

atp sources in working muscle
ATP sources in working muscle

At the beginning of exercise, muscle fibers immediately use stored ATP

For the next 15 seconds, muscle fibers turn to the creatine phosphate.

This system dominates in events such as the 100m dash or lifting weights.

atp sources in working muscle con t
ATP sources in working muscle cont.

After the phosphagen system is depleted, the process of anaerobic glycolysiscan maintain ATP supply for about 45-60s.

Glycogen stored in muscles  Glucose  2pyruvic acid + 2 ATPs

2 Pyruvic acid  2 lactic acid

Lactic acid diffuses out of muscles blood  liver  Glucose (by gluconeogenesis) blood  muscles

* It usually takes a little time for the respiratory and cardiovascular systems to catch up with the muscles and supply O2 for aerobic metabolism.

slide26
Anaerobic metabolism is inefficient:

1- Large amounts of glucose are used for very small ATP returns.

2- Lactic acid is produced leading to muscle fatigue

Type of sports uses anaerobic metabolism?

Sports that requires bursts of speed and activity e.g. basketball.

ATP sources in working muscle cont.

slide27
Aerobic metabolism

Occurs when the respiratory & cardiovascular systems have “caught up with” the working muscles.

During rest and light to moderate exercise, aerobic metabolism contributes 95% of the necessary ATP.

Compounds which can be aerobically metabolized include:

Fatty acids, pyruvic acid (made via glycolysis) & amino acids.

ATP sources in working muscle cont.

the cori cycle
The Cori cycle

Liver converts lactate into glucose via gluconeogenesis

The newly formed glucose is transported to muscle to be used for energy again

the glucose alanine cycle
The glucose-alanine cycle

Muscles produce:

1- Pyruvatefrom glycolysis during exercise

2- NH2produced from normal protein degradation

Pyruvate + NH2 Alanine

Alanineis transported through the blood to liver

Liver converts alanine back to pyruvate

Alanine – NH2 = Pyruvate

Pyruvateis converted to glucose (gluconeogenesis).

Glucose is transported to muscle to be used for energy again.

Liver converts NH2 to urea for excretion (urea cycle)