Bioenergetics Chapter 2

Study Notes

Metabolism is the total sum of all chemical reactions in the body, including energy involved in digestion and micro reactions.
Two main types:
- Anabolic: synthesis or building of molecules. Examples include insulin's role in building adipose tissue (fat).
- Catabolic: breakdown of molecules. Example includes bioenergetics, the process converting food (fats, carbohydrates, protein) into usable energy forms at rest or during exercise.
ATP (adenosine triphosphate)
- Not a long-term energy store. (~90 g total at rest)
- Resting intramuscular concentration is 5 mmol/kg.
- Muscle contraction can increase cellular ATP demand 500-1000x.
Macronutrients:
- Proteins: 4 Calories/gram
- Carbohydrates: 4 Calories/gram
- Fats: 9 Calories/gram
- Carbohydrates and fats are the primary energy sources during exercise.
- Carbohydrates are more important for elite athletes.

Enzymes are protein molecules that speed up reactions without being consumed.
Enzymes lower the activation energy required for a reaction.
The active site is where the enzyme's magic occurs.
Enzymes can function both anabolically and catabolically.
Two factors regulating the speed of enzyme activity:
- pH: Each enzyme has an optimal pH where it functions best.
- Temperature: High temperatures can denature enzymes.
Energy systems:
- Phosphagen (ATP-PCR, Phosphocreatine): The first and shortest system, used during the initial seconds of activity (less than 3 seconds). Free-floating ATP is used.
- Glycolytic-Lactate: A second system using two types of pathways:
  - Fast Glycolysis (anaerobic): utilized during short, high-intensity activities like plyometrics, weightlifting, or sprinting.
  - Slow Glycolysis (aerobic): used in activities like walking, swimming, or cycling.
- Oxidative Phosphorylation (Mitochondrial Respiration): The third and most efficient system; used for longer duration exercise.

Phosphagen system: uses phosphocreatine (PCR) to generate ATP, a one-step process involving creatine kinase.
Anaerobic glycolysis: a two-step process with creatine kinase involved and negative feedback system when ATP levels increase, creatine kinase activity decreases.
Creatine supplementation increases intramuscular stores of PCR, allowing for quicker energy release.

Four stages of CHO metabolism:
- Stage 1: Glycolysis (anaerobic) - breaking down glucose or glycogen into pyruvate to produce ATP. This stage has two phases: energy investment and energy payoff.
- Stage 2: Conversion of pyruvate to Acetyl-CoA (aerobic) - pyruvate is converted into acetyl-CoA to prepare for the Krebs cycle.
- Stage 3: Krebs Cycle( Aerobic) - Series of reactions where energy is harvested from Acetyl-CoA. Electron carriers NADH and FADH2 are produced.
- Stage 4: Electron Transport Chain (ETC) (Aerobic) - Electron carriers (NADH and FADH2) generate ATP via oxidative phosphorylation.

Lactate is a byproduct of anaerobic glycolysis.
Lactate threshold is the point where lactate accumulation increases markedly, indicating a transition from primarily aerobic to anaerobic metabolism.
Aerobic glycolysis and the Krebs cycle produce ATP through oxidative phosphorylation.
Respiration quotient (RQ) relates how the body is burning energy.