Upload
beatrice-horn
View
223
Download
3
Tags:
Embed Size (px)
Citation preview
Aerobic & Anaerobic Aerobic & Anaerobic Metabolism in MusclesMetabolism in Muscles
ObjectivesObjectives
Recognize the importance of ATP as Recognize the importance of ATP as energy source in skeletal muscle.energy source in skeletal muscle.
Understand how skeletal muscles Understand how skeletal muscles derive and utilize ATP for energy.derive and utilize ATP for energy.
Differentiate between energy Differentiate between energy metabolism in red and white muscle metabolism in red and white muscle fibers.fibers.
ATP or ATP or adenosine triphosphateadenosine triphosphate is the energy currency used by is the energy currency used by our body everyday to perform a number of tasks:our body everyday to perform a number of tasks:
METABOLISM: METABOLISM: EnergyEnergy ReleaseRelease
Maintain body temperature
• Repair damaged cells
• Digestion of food
• Mechanical work – movement
ATP ↔ ADP + Energy
ATP …….. Contd.ATP …….. Contd.
The nucleotide coenzyme The nucleotide coenzyme adenosineadenosine triphosphate (ATP)triphosphate (ATP) is the most important form is the most important form of chemical energy stored in cellsof chemical energy stored in cells
Breakdown of ATP into ADP+POBreakdown of ATP into ADP+PO44 releases releases energyenergy
Muscles typically Muscles typically store limitedstore limited amounts of ATP amounts of ATP – enough to power – enough to power 4-6s 4-6s of activityof activity
So resting muscles must have energy stored in So resting muscles must have energy stored in other ways.other ways.
ATP Is GeneratedATP Is GeneratedThrough 3 Energy SystemsThrough 3 Energy Systems
1.1. ATP-PCr system ATP-PCr system
2.2. Glycolytic systemGlycolytic system
3.3. Oxidative systemOxidative system
The process that facilitates muscular contraction is entirely dependent on body’s ability to provide & rapidly
replenish ATP
INTERACTION OF ENERGY INTERACTION OF ENERGY SYSTEMSSYSTEMS
Immediate Short-term Long-term
100%%
Cap
acit
y o
f E
ner
gy
Sys
tem
10 sec 30 sec 2 min 5+ min
Energy Transfer Systems and ExerciseEnergy Transfer Systems and Exercise
Aerobic Energy System
Anaerobic Glycolysis
ATP - CP
Exercise Time
Energy Systems Energy Systems for Exercisefor Exercise
Energy SystemsEnergy SystemsMole of Mole of ATP/minATP/min
Time to Time to FatigueFatigue
Immediate:Immediate: ATP - PCr ATP - PCr
(ATP & phosphocreatine)(ATP & phosphocreatine)445 to 10 sec5 to 10 sec
Short Term:Short Term: GlycolyticGlycolytic
(Glycogen-Lactic Acid)(Glycogen-Lactic Acid)2.52.51 to 2 min1 to 2 min
Long Term:Long Term: OxidativeOxidative11Unlimited Unlimited
timetime
Energy RequirementsEnergy Requirements
The three energy systems often operate The three energy systems often operate simultaneously during simultaneously during physical activity.physical activity.
Relative contribution of each system to Relative contribution of each system to total energy requirement differs markedly total energy requirement differs markedly depending on exercise depending on exercise intensityintensity & & durationduration..
Magnitude of energy from anaerobic sources Magnitude of energy from anaerobic sources depends on depends on person’s capacity and tolerance person’s capacity and tolerance for lactic acid accumulation for lactic acid accumulation (Athletes are (Athletes are trained so that they will have better tolerance trained so that they will have better tolerance for lactic acid) for lactic acid) ..
As exercise intensity diminishes and duration As exercise intensity diminishes and duration extends extends beyond 4 minutes,beyond 4 minutes, energy more energy more dependent on dependent on aerobic metabolismaerobic metabolism..
Energy MetabolismEnergy Metabolism
AerobicAerobicWith oxygenWith oxygenSource of energy: Source of energy:
mainly mainly fatty fatty acidsacids, then , then carbohydratecarbohydrate
COCO22, H, H22O & ATPO & ATP
AnaerobicAnaerobic– Without oxygenWithout oxygen– Source of Source of
energy: energy: Carbohydrate Carbohydrate (glycolysis)(glycolysis)
– Lactate & ATPLactate & ATP
What factors contribute to What factors contribute to muscle fatigue?muscle fatigue?
Fatigued muscle no longer contracts due Fatigued muscle no longer contracts due to:to: Build up of lactic acid (low pH of Build up of lactic acid (low pH of
sarcoplasm)sarcoplasm)Exhaustion of energy resources (Exhaustion of energy resources (
ADP & ADP & ATP) ATP)Ionic imbalance: muscle cells is Ionic imbalance: muscle cells is
less responsive to motor neuronal less responsive to motor neuronal stimulationstimulation
Muscle FatigueMuscle Fatigue
How would a fatigued muscle be How would a fatigued muscle be able again to contractable again to contract
Recovery period: Begins immediately after activity ends
Oxygen debt (excess post-exercise oxygen consumption)◦Amount of oxygen required during resting period to restore muscle to normal conditions
What are the mechanisms What are the mechanisms by which muscle fibers by which muscle fibers obtain energy to power obtain energy to power
contractions?contractions?
Muscles and Fiber TypesMuscles and Fiber TypesWhite muscle : White muscle : (glycolytic(glycolytic))
mostly fast fibersmostly fast fiberspale (pale (e.g.,e.g., chicken breast) chicken breast)
Red muscleRed muscle: : (oxidative)(oxidative)mostly slow fibersmostly slow fibersdark (dark (e.g.,e.g., chicken legs) chicken legs)
Most human muscles:Most human muscles:mixed fibersmixed fiberspinkpink
Fast versus Slow FibersFast versus Slow Fibers
Type I
Type II
Abundant mitochondriaAbundant mitochondriaExtensive capillary supplyExtensive capillary supplyHigh concentrations of myoglobinHigh concentrations of myoglobinCan contract for long periods of timeCan contract for long periods of timeFatigue resistantFatigue resistantObtain their ATP mainly from Obtain their ATP mainly from FA FA --
oxidation,oxidation, TCA cycle, and the ETC TCA cycle, and the ETC
Slow fibers:Slow fibers:
Large glycogen reservesLarge glycogen reservesRelatively few mitochondriaRelatively few mitochondriaProduce rapid, powerful contractions of Produce rapid, powerful contractions of
short durationshort durationEasily fatiguedEasily fatiguedObtain their ATP mainly from Obtain their ATP mainly from Anaerobic Anaerobic
glycolysisglycolysis
Fast fibersFast fibers
ENERGY REQUIREMENTS ENERGY REQUIREMENTS AND SOURCE OF ENERGY AND SOURCE OF ENERGY FOR SKELETAL MUSCLEFOR SKELETAL MUSCLE
( Resting vs. Working)( Resting vs. Working)
ATP Use in the Resting Muscle CellATP Use in the Resting Muscle Cell
ATP is necessary for cellular housekeeping duties, ATP is necessary for cellular housekeeping duties, e.g.:e.g.:ATP is used for ATP is used for glycogenesisglycogenesis (storage form of (storage form of
glucose)glucose)ATP is used to create another energy storage ATP is used to create another energy storage
compound called compound called creatine phosphatecreatine phosphate
Resting Muscle and Resting Muscle and the Krebs Cyclethe Krebs Cycle
Resting muscle fibers typically takes up fatty acids Resting muscle fibers typically takes up fatty acids from the blood stream.from the blood stream.
Inside the muscle fiber, the Inside the muscle fiber, the FA’s are oxidized (in the are oxidized (in the mitochondriamitochondria) to produce ) to produce Acetyl-CoAAcetyl-CoA & several & several molecules of NADH and FADH2molecules of NADH and FADH2
Acetyl-CoA will then enter the Acetyl-CoA will then enter the Krebs cycle Krebs cycle (in the (in the mitochondriamitochondria)) COCO22, , ATP,ATP, NADH, FADH2, and NADH, FADH2, and oxaloacetateoxaloacetate
NADH and FADH2 will enter NADH and FADH2 will enter the Electron the Electron Transport Chain. Transport Chain. (in the inner (in the inner mitochondrialmitochondrial membrane)membrane) synthesis of synthesis of ATPATP
Figure 10–20a
ATP use in ATP use in Working MuscleWorking Muscle
As we begin to exercise, we almost immediately As we begin to exercise, we almost immediately use our stored ATPuse our stored ATP
For the For the next 15 secondsnext 15 seconds or so, we turn to the or so, we turn to the creatine-phosphate.creatine-phosphate.
This system dominates in events such as This system dominates in events such as the 100m dash or lifting weights.the 100m dash or lifting weights.
Working MuscleWorking Muscle After the phosphagen system is depleted, the muscles After the phosphagen system is depleted, the muscles
must find another ATP source.must find another ATP source. **The process of The process of anaerobic metabolism anaerobic metabolism can maintain ATP can maintain ATP
supply for supply for about 45-60s.about 45-60s. Glycogen Glycogen Glucose Glucose 2 2 pyruvic acid pyruvic acid (2 ATP + 2 (2 ATP + 2
NADH)NADH) 2 Pyruvic acid 2 Pyruvic acid 2 2 lactic acid lactic acid (2 NAD(2 NAD++)) Lactic acid diffuses out of muscles Lactic acid diffuses out of muscles blood blood taken by taken by
the liver the liver Glucose (by gluconeogenesis) Glucose (by gluconeogenesis) blood blood taken by the muscle againtaken by the muscle again
* * It usually takes a little time for the respiratory and cardiovascular It usually takes a little time for the respiratory and cardiovascular systems to catch up with the muscles and supply Osystems to catch up with the muscles and supply O22 for aerobic for aerobic
metabolism.metabolism.
Muscle MetabolismMuscle Metabolism
Figure 10–20c
Anaerobic Metabolism, Anaerobic Metabolism, continuedcontinued……
Anaerobic metabolism is inefficient… Why?Anaerobic metabolism is inefficient… Why?Large amounts of glucose are used for very small Large amounts of glucose are used for very small
ATP returns.ATP returns.Lactic acid is produced whose presence Lactic acid is produced whose presence
contributes to muscle fatiguecontributes to muscle fatigue
Which type of sports uses anaerobic Which type of sports uses anaerobic metabolism?metabolism?Sports that requires bursts of speed and activity, Sports that requires bursts of speed and activity,
e.g., basketball.e.g., basketball.
Aerobic MetabolismAerobic Metabolism Occurs when the respiratory and cardiovascular Occurs when the respiratory and cardiovascular
systems have “caught up with” the working systems have “caught up with” the working muscles.muscles. Prior to this, some aerobic respiration will occur thanks Prior to this, some aerobic respiration will occur thanks
to the muscle protein, to the muscle protein, myoglobinmyoglobin, which binds and , which binds and stores oxygen.stores oxygen.
During During restrest and and light to moderate light to moderate exercise, exercise, aerobic metabolism contributes 95% of the aerobic metabolism contributes 95% of the necessary ATP.necessary ATP.
Compounds which can be aerobically metabolized Compounds which can be aerobically metabolized include:include: Fatty acids, Fatty acids, Pyruvic acid (made via glycolysis), and Pyruvic acid (made via glycolysis), and
amino acids.amino acids.
THE CORI CYCLETHE CORI CYCLE&&
THE GLUCTHE GLUCOOSE-SE-ALANINE CYCLEALANINE CYCLE
The Cori cycleThe Cori cycle
LiverLiver converts converts lactatelactate into into glucoseglucose via via gluconeogenesisgluconeogenesis
The newly formed The newly formed glucose is transported to glucose is transported to muscle to be used for muscle to be used for energy againenergy again
The glucose-alanine The glucose-alanine cyclecycle
Muscles produce:Muscles produce: PyruvatePyruvate from glycolysis during exercise and from glycolysis during exercise and
NH2 NH2 produced from normal protein degradation produced from normal protein degradation produce produce AlanineAlanine
Pyruvate + NH2 Alanine
This alanine is transported through the blood to This alanine is transported through the blood to liverliver
Liver converts alanine back to pyruvateLiver converts alanine back to pyruvate
Alanine – NH2 = Pyruvate
Pyruvate is used in gluconeogenesisPyruvate is used in gluconeogenesis The newly formed glucose is transported to The newly formed glucose is transported to
muscle to be used for energy againmuscle to be used for energy again
The Glucose-Alanine The Glucose-Alanine CycleCycle
What happened to NHWhat happened to NH22??Liver converts it to urea Liver converts it to urea for excretion (urea cycle)for excretion (urea cycle)