Bioenergetics: How energy is utilized in living organisms

Metabolism

  • Sum of all chemical reactions that occur in body (require energy) (BMR)
  • Catabolic reactions
  • breakdown of molecules
  • carbs, protein, fat release energy
  • Anabolic reactions
  • synthesis of molecules (building up)
  • building muscle, storing carbs. or fat
  • Bioenergetics
  • converting foodstuffs (fats, proteins, carbohydrates) into energy or storing them

Cell Structure

  • Cell membrane
  • protective barrier b/t interior of cell & extra-cellular fluid
  • Nucleus
  • contains DNA/genes that regulate protein synthesis
  • Cytoplasm
  • fluid portion of cell
  • contains organelles (mitochondria)

Energy Transformation

  • Forms of Energy
  • Electrical
  • Mechanical
  • Thermal
  • Chemical
  • 1st Law of Thermodynamics
  • “energy is neither created nor destroyed, just transferred from one form to another”
  • Energy stored in food, transferred to body & stored
  • when need energy for mechanical work we extract it from carbs, fat, or protein

Enzymes

  • Catalysts regulate speed of reaction
  • lower the “energy of activation”
  • rate limiting enzyme
  • Interact with specific substrates
  • lock & key

Factors that regulate enzyme activity

  • Temperature (warm up)
  • Q10 Effect
  • pH (fatigue, buffering agents: sodium bicarbonate)

Enzymes Lower Energy of Activation

Energy for Exercise

  • Carbohydrates (glucose)
  • stored as glycogen (liver & muscle)
  • most rapid form of energy
  • only fuel used anaerobically
  • can also be used aerobically
  • *limited stores; can be depleted
  • Fats (fatty acids & glycerol)
  • stored as triglycerides (adipose/muscle)
  • ideal fuel, unlimited, but requires O2
  • Proteins (amino acids)
  • not primary energy source
  • 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: anaerobic
  • Glycolysis: anaerobic (can continue into an aerobic process)
  • Aerobic System: Krebs cycle & electron transport chain

1. “ATP/PC” or “Phosphagen” system

  • Immediate energy source; onset of exercise
  • Approx. 10 sec. of energy
  • System is “anaerobic” & occurs in cytoplasm
  • Replenishment occurs during recovery (3 min): aerobically
  • Short sprint, lift (5 reps), explosive movements

2. Glycolysis

  • Breakdown of “glucose”
  • Occurs in “cytoplasm” of cell
  • “Anaerobic” process
  • Very little energy (ATP) produced,but very quick; “pyruvate” or “lactate” formed
    depending on availability of O2

2 Stages

  • Energy investment phase; requires ATP
  • Energy generation phase
  • produces ATP, “NADH” (carrier molecule), & pyruvate or lactate

Key Points in Glycolysis

  • Define – breakdown of ONLY glucose to make ATP
  • Energy put in to get going (phosphorylation)
  • Enzymes needed throughout
  • H+ ions pulled off substrate (oxidation) (picked up by NAD)
  • Good – have energy in them
  • Bad – if can’t use them, they turn pyruvate into lactic acid
  • Lactic acid lowers pH; effect on enzymes???
  • Small amount of ATP is formed 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
  • only molecule that can enter Krebs cycle

2 Processes:

  • Krebs cycle
  • completes “oxidation” of substrates & produces NADH to enter…
  • Electron Transport Chain

Electron Transport Chain

  • Hydrogens & Electrons are removed from NADH (oxidized)
  • energy in electrons used to concentrate H+
  • H+ then diffuses back across membrane giving energy to phosphorylate ADP producing ATP
  • H+ then combines with O2 to form water (NO LACTIC ACID)
  • 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
  • aerobic process
  • Acetyl CoA is formed from substrates; Acetyl CoA enters “Krebs Cycle” & is oxidized
  • H+ & electrons are removed & carried to ….Electron Transport Chain
  • energy in electrons/H+ are used to combine ADP with P to make ATP (oxidative phosphorylation)
  • oxygen combines with H+ to form water & CO2

Without oxygen

  • H+ builds up in ETC
  • pH drops & Krebs cycle & ETC enzymes are inhibited & shut down
  • aerobic metabolism slows
  • NADH can’t drop off more H+
  • H+ brought to pyruvate (creates lactic acid)
  • Now we can only rely on glycolysis to make more ATP
  • 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

Interaction Between Aerobic and Anaerobic ATP Production

  • Energy to perform exercise comes from an interaction b/t aerobic & anaerobic pathways
  • Short-term, high-intensity
  • > contribution of anaerobic energy systems
  • Long-term, low to moderate-intensity exercise
  • majority of ATP produced from aerobic sources
  • Always combination of both, which one dominates

Where is the Practicality to ATP/PC & Glycolysis?

  • Student: I am thinking about supplementing “creatine”, the bottle says it builds muscle. What do you know about creatine what is it, how does it work, does it work? What are possible limitations?
  • Student: I read that B vitamins (niacin) give us energy, should I supplement them to perform better. What does niacin do?
  • Student: I notice when I lift weights and push myself really hard, I feel a burning sensation in my legs. What is that & is it dangerous, why is it occuring?
  • Student: What causes me to fatigue during exercise (especially high intensity exercise like sprinting)? Is there anything I can do to delay this fatigue?
  • Student: Why do we need oxygen to live, what does it do? What happens, if I cant get enough during exercise?
  • Student: I read that when I weight train for increasing strength, I should weight about 3 minutes between sets, why this amount of time?
  • Student: If I am training for the 400 m (<90 sec), is there any benefit to aerobic training?
  • Student: I was at the “Super Supplement Store” and they were selling “pyruvate” and “Acetyl CoA”. What is that stuff and how does it work? If it works, what would it do?
  • Student: Is basketball an aerobic or anaerobic sport?
  • We will make this much more practical when we talk about developing exercise programs, but we first must understand energy systems

Questions on Material

  • The primary function of the krebs cycle is?
  • Explain the role of NAD
  • Where is energy stored in substrates?
  • Describe the 3 Methods for producing ATP.
  • What is the function of ETC?
  • What is contribution of aerobic & anaerobic production at 20, 60 secs, 3 min, 10 min?
  • What is a rate limiting enzyme?
  • What controls these enzymes?
  • Questions on Material, Explain the following
  • Metabolism
  • Anabolic
  • Catabolic
  • Bioenergetics
  • 1st law of thermodynamics
  • Forms of energy
  • Cell membrane, cytoplasm, mitochondria
  • Enzymes, substrates
  • Energy of activation