Download Bioenergetics

Bioenergetics: How energy is utilized in living organisms
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Metabolism
Sum of all chemical reactions that occur in body (require energy) (BMR)
o Basal metabolic rate ~70% of energy
o Physical activity ~25% of energy
o Thermic effect of food ~5%
Catabolic reactions
o breakdown of molecules
o carbs, protein, fat release energy
Anabolic reactions
o synthesis of molecules (building up)
o building muscle, storing carbs. or fat
Bioenergetics
o converting foodstuffs (fats, proteins, carbohydrates) into energy or storing them
Cell Structure
Cell membrane
o protective barrier b/t interior of cell & extra-cellular fluid
Nucleus
o contains DNA/genes that regulate protein synthesis
Cytoplasm
o fluid portion of cell
o contains organelles (mitochondria)
Energy Transformation
Forms of Energy
o electrical
mechanical
o thermal
chemical
1st Law of Thermodynamics
o “energy is neither created nor destroyed, just transferred from one form to another”
Energy stored in food, transferred to body & stored
o when need energy for mechanical work we extract it from carbs, fat, or protein
Enzymes
Catalysts regulate speed of reaction
o lower the “energy of activation”
o rate limiting enzyme
Interact with specific substrates
o lock & key
Factors that regulate enzyme activity
o Temperature (warm up)
o Q10 Effect
pH (fatigue, buffering agents: sodium bicarbonate)
Enzymes Lower Energy of Activation
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Energy for Exercise
Carbohydrates (glucose)
o stored as glycogen (liver & muscle)
o most rapid form of energy
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o only fuel used anaerobically
o can also be used aerobically
o *limited stores; can be depleted
Fats (fatty acids & glycerol)
o stored as triglycerides (adipose/muscle)
o ideal fuel, unlimited, but requires O2
Proteins (amino acids)
o not primary energy source
o no storage form; found in muscle
Usable Energy Source for Body
Adenosine triphosphate (ATP)
Energy trapped in phosphate bonds (chemical energy)
Carbs, fats, proteins must be catabolyzed into this form before our body can use energy
Muscle stores limited amounts (3-5 sec)
3 Mechanisms for Formation of ATP
ATP-PC or Phosphogen system
o anaerobic
Glycolysis
o anaerobic (can continue into an aerobic process)
Aerobic System
o Krebs cycle & electron transport chain
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1. “ATP/PC” or “Phosphagen” system
Immediate energy source
o onset of exercise
Approx. 10 sec. of energy
System is “anaerobic” & occurs in cytoplasm
Replenishment occurs during recovery (3 min)
o aerobically
Short sprint, lift (5 reps), explosive movements
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2. Glycolysis
Breakdown of “glucose”
Occurs in “cytoplasm” of cell
“Anaerobic” process
Very little energy (ATP) produced, but very quick
“pyruvic acid” or “lactic acid” formed depending on availability of O2
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2 Stages
Energy investment phase
o requires ATP
Energy generation phase
o produces ATP, “NADH” (carrier molecule), & pyruvic acid or lactic acid
Key Points in Glycolysis
Define – breakdown of ONLY glucose to make ATP
Energy put in to get going (phosphorylation)
Enzymes needed throughout
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H+ ions pulled off substrate (oxidation) (picked up by NAD)
o Good – have energy in them
o Bad – if can’t use them, they turn pyruvate into lactic acid
Lactic acid lowers pH
o effect on enzymes???
Small amount of ATP is formed
o But very quickly
Last 2-3 minutes max, anaerobic process (no oxygen present) then need other source of energy
3. Aerobic System (Use of O2 to form of ATP)
Occurs in mitochondria
Substrates converted to Acetyl CoA
o only molecule that can enter Krebs cycle
2 Processes:
Krebs cycle
o completes “oxidation” of substrates & produces NADH to enter…
Electron Transport Chain
Electron Transport Chain
Hydrogens & Electrons are removed from NADH (oxidized)
o energy in electrons used to concentrate H+
o H+ then diffuses back across membrane giving energy to phosphorylate ADP producing ATP
o H+ then combines with O2 to form water (NO LACTIC ACID)
o final product of aerobic metabolism: Water, ATP, & CO2
 process called oxidative phophorylation
 all occurs in mitochondria of cell (aerobic process)
 as long as oxygen is available the process can continue
Review of Aerobic Metabolism
Occurs in mitochondria of all cells
o aerobic process
Acetyl CoA is formed from substrates
Acetyl CoA enters “Krebs Cycle”
o oxidation of acetyl CoA
o H+ & electrons are removed & carried to ….
Electron Transport Chain
o energy in electrons/H+ are used to combine ADP with P to make ATP (oxidative
phosphorylation)
o oxygen combines with H+ to form water & CO2
So What Happens if We Can’t Get Enough Oxygen to Mitochondria?
Without oxygen
o H+ builds up in ETC
o pH drops & Krebs cycle & ETC enzymes are inhibited & shut down
o aerobic metabolism slows
o NADH can’t drop off more H+
o H+ brought to pyruvate (creates lactic acid)
Now we can only rely on glycolysis to make more ATP
o but it eventually shuts down by H+ & lactic acid
ATP/PC system is already used up
Exercise must stop or slow down b/c there is no way to form ATP
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Interaction Between Aerobic and Anaerobic ATP Production
Energy to perform exercise comes from an interaction b/t aerobic & anaerobic pathways
Short-term, high-intensity
o > contribution of anaerobic energy systems
Long-term, low to moderate-intensity exercise
o majority of ATP produced from aerobic sources
Always combination of both, which one dominates
Questions on Chapter 3?????