9/25c Metabolic Pathways for Aerobic Exercise (Biomedical Sciences) Flashcards
muscles are metabolic machines and what is their reason for being?
convert chemical energy into mechanical work
- Catabolism of fuel
- ATP
- Force Production
- Movement
intimate relationship between muscles and capillaries
there are many capillaries that lie within the muscles running throughout everything!
Different muscle types:
Type I
Type IIa
Type IIx
Type I muscle fibers
-slow oxidative
-slow contraction speed
-slow relaxation speed
-few fibers
-high concentration myoglobin (makes them red)
-high structural capillary density
-fatigue very slowly
-low glycolytic
-high oxidative
-high mitochondrial
POSTURAL MUSCLES
Type IIx muscle fibers
-lowest capillary density structure
-high concentration glycolytic enzymes
-lowest concentration oxidative enzymes
-lowest mitochondrial content
-Fastest contraction speed
-lowest concentration myoglobin (whitest/leanest meat)
-Fatigue very easily
-many fibers
POWER MUSCLES
Type IIa muscle fibers
-low capillary density structure
-high concentration glycolytic enzymes
-low concentration oxidative enzymes
-low mitochondrial content
-Fast contraction speed
-lower concentration myoglobin (white meat)
-many fibers
POWER MUSCLES
ATP function
adenine with 3 phosphate groups > hydrolysis > ADP + Phosphate + ENERGY (used to produce mechanical work)
ATP + H2O > ADP + Pi + Free Energy
resting skeletal muscle requirements of ATP?
- ion pumps (Na+-, K+, Ca++, SERCA)
- RNA and protein synthesis
- Fuel Storage
- Transport of substances
- signaling to regulate cell processes
- 1mmol/kg/min
Contracting skeletal muscle requirements of ATP
– All those in resting
– Myosin ATPase - enzyme that breaks down ATP in order to power contraction
-240mmol/kg/min
throughout the entire range of muscle metabolic activity level what is the ATP level?
it stays at 8mM
- the concentration doesn’t change even when there is a really high consumption rate
- Pathways for ATP regeneration
3 pathways whereby ATP is regenerated
- Phosphocreatine
- Anaerobic Glycolysis
- Oxidative Phosphorylation
Phosphocreatine reaction and its function
ADP + PCr + H+ ATP + Cr
TEMPORAL BUFFER and Spatial buffer
-rapid reaction, supplies about 10 seconds worth of energy at max effort
-takes 1 second to get to peak capacity
-HIGH power, LOW capacity
-ATP and ADP don’t diffuse rapidly through the cell, but PCr and Cr do, so they shuttle phosphate groups from mitochondria to the ATPase where they are broken down
-Cr is synthesized in the liver and absorbed in the diet
what is phosphocreatine imperative for?
the initial transition between rest and exercise
anaerobic glycolysis key factors
- Glucose/glycogen broken down into lactate in the absence of oxygen
- Moderate power and capacity (not as rapid as PCr), lasts on the order of minutes
- associated with acidosis
- takes 5 seconds to get to peak output
- important during heavy exercise (>60% VO2max)
- when oxygen is insufficient to support oxidative phosphorylation
process of anaerobic glycolysis
Glycolysis leads to 2 possible endpoints
- pyruvate that enters TCA cycle -> Oxidative phosphorylation
- OR pyruvate gets broken into lactate
Steps for Anaerobic Glycolysis (two sources of glucose)
A.
1. Glucose in the blood (5mmol)
2. glucose transporters move glucose into the muscle in response to: insulin and/or exercise
3. Glucose goes right into glycolysis then pyruvate and lactate (acidosis)
B.
- Glycogen stored in muscle (carbohydrate stored in muscle)
- glycogen is broken down through glycolysis
- pyruvate + lactate is the end result (acidosis)
oxidative phosphorylation
- aerobic metabolism
- Substrate (Lipid, Carb, Protein) + O2 -> CO2 + H2O + 5 ATP
- LOW power system, HIGH capacity
- takes 2 minutes to get to peak output
- rate is measured by rate of oxygen consumption (directly proportional to workload) - VO2max
- primary means of energy production
two processes included in oxidative phosphorylation
- TCA cycle/kreb/citric acid: produces ATP, but mostly reducing equivalents (strips electrons from substrate)
- Electron Transport Chain: reducing equivalents go to electron transport chain, transfer of electrons until electron is transferred from oxygen (terminal electron acceptor) turning into water and that powers proton gradient that adds phosphate onto ADP to create ATP
lipid with oxidative phosphorylation
very important for oxidative phosphorylation
- at rest, the primary fuel source for oxidative phosphorylation is LIPID
- -slower than glucose/glycogen pathways…but a HUGE capacity
- 100,000kcals available through oxidation of lipid
- 130 ATP per molecule of palmitic acid
- Beta oxidation cycle
Triglycerides and oxidative phosphorylation
triglycerides are broken through lipolysis into free fatty acids and glycerol
- free fatty acids go into the beta oxidation cycle (where it enters depends on what fatty acid it is)
- glycerol goes into glycolysis
where do you see high levels of lipids in muscle?
- old and sedentary and diseased (extra storage site)
- highly trained (turn over rate because it’s a fuel source to power activity)
- *lipid paradigm
Beta oxidation cycle
output goes into the TCA cycle then electron transport chain to generate ATP
Glucose with oxidative phosphorylation
- burn at a very high intensity
- Pyruvate from acetyl co a
- then TC and ETC
- 36 molecules of ATP per molecule of glucose
- limited capacity, 500kcal per glycogen
protein as a substrate for oxidative phosphorylation
- enters cycle based on what kind of protein it is
- proteins are broken down via proteolysis
- they get broken into amino acids
- amino acids are deaminated
- enter at different points of TCA cycle and result in reducing equivalents to electron transport chain and create ATP
- minor source of energy during exercise because we need muscles
- used in gluconeogenesis
oxidative phosphorylation in a nutshell
- primary means of energy production
- lipids, carbs, and proteins can all be used as fuel sources
- -lipids are most important at rest
- -carbs are most important during exercise
- -proteins are most important during disease states and starvation
energy sources and exercise
- percentage of energy that is being produced through aerobic pathways increases as duration increases
- percentage of energy that is being produced through anaerobic pathways as decreases as duration of activity increases
-as duration increases, relying more on aerobic energy production and when we want more high intensity workouts we rely on anaerobic energy
as intensity of the workout increases, what happens?
as duration of the workout increases, what happens?
- there is a greater reliance on carbohydrates instead of lipids
- there is a greater reliance on lipids instead of carbohydrates
what’s the best intensity of a workout to burn fat?
- with lower intensity you are burning more lipid, but you have to do the work for a long time
- BUT with high intensity workout for 30 minutes, you get more out of the high intensity workout (absolute number of calories burned is higher)
changes with training: anaerobic
high intensity, short duration activities
- Increased anaerobic substrates
- –ATP, PCr, Creatine, Glycogen
- Increased quantity and activity of key glycolytic enzymes
changes with training: aerobic
- moderate intensity, long duration
- metabolic
- -Increase in # of mitochondria
- -increase in oxidation of fats at rest and at submax exercise
- –>increase in fat mobilizing and metabolic enzymes
- –>decrease catecholamine release
- –>preserves glycogen stores/increases endurance
- -increases ability to oxidize carbs at max exercise
what is the significance of catecholamine release?
catecholamines are associated with increased reliance on carbohydrates
