Energy Systems Overview

Mitochondria

  • Powerhouse of the cell.
  • Generates ATP through aerobic/cellular respiration.
  • Self-replicates during high demand.
  • Important in apoptosis.
  • Cristae increase surface area for ATP production.

ATP

  • Energy currency.
  • Links energy-yielding and requiring functions.
  • Carbs + Fats + Proteins \rightarrow ATP \rightarrow Physiological functions + Heat
  • ATP \rightarrow ADP + Phosphate

Metabolism

  • Energy transformation in the body.
  • Energy cannot be created or destroyed, only transformed.

Catabolism

  • Energy releasing.
  • ATP \rightarrow ADP + Phosphate + Energy

Anabolism

  • Energy requiring.
  • ADP + Phosphate + Energy \rightarrow ATP

Macronutrients

  • Carbohydrates (CHO): Rapid energy source (glucose, muscle glycogen).
  • Fats (CHO): Prolonged exercise energy (triglycerides in adipose tissue).
  • Proteins: Limited energy use, not efficient.

Cellular Respiration

  • Metabolic pathway using glucose to produce ATP in mitochondria.
  • Three steps:
    • Glycolysis.
    • Citric acid cycle (Krebs cycle).
    • Electron transport chain.
  • Net ATP gain: 30-32 per glucose molecule.

Glycolysis

  • Occurs outside the mitochondria (in the cytosol).
  • Anaerobic.
  • Net gain: 2 ATP + 2 NADH + H + 2 pyruvate.
  • Rate-limiting enzyme: Phosphofructokinase.

Krebs Cycle (Citric Acid Cycle)

  • Aerobic (requires oxygen).
  • Occurs in the mitochondria.
  • Net gain: 2 ATP + NADH + FADH + 4 CO2.
  • Rate-limiting enzyme: Isocitrate dehydrogenase.

Electron Transport Chain

  • Aerobic.
  • Occurs in the mitochondria.
  • Net gain: 26-28 ATP.
  • Rate-limiting enzyme: Cytochrome oxidase.

Intracellular Regulators

  • Rate-limiting enzymes: Phosphofructokinase, isocitrate dehydrogenase, cytochrome oxidase.
    • Stimulators: Increase ATP production (e.g., AMP, ADP, Phosphate, higher pH).
    • Inhibitors: Decrease ATP production (e.g., ATP, Creatine Phosphate, Citrate, lower pH).
  • Phosphorylase breaks down glycogen into glucose.

Extracellular Regulators

  • Hypothalamus stimulates the sympathetic nervous system.
  • The pancreas decreases insulin and increases glucagon.
  • Increased epinephrine and norepinephrine to stimulate ATP production.

Hormonal Regulators

  • Key hormones: Glucagon, epinephrine, norepinephrine, growth hormone, cortisol.
  • Secondary hormones: Growth hormone-releasing hormone, thyroid-releasing hormone, thyroid-stimulating hormone, corticotropin-releasing hormone, adrenocorticotrophic hormone.

Gluconeogenesis

  • Creation of new glucose from non-carb sources (occurs in the liver).
    • Triglycerides to glycerol to glucose.
    • Lactic acid/pyruvate to glucose.
    • Alanine to pyruvate to glucose (produces ammonia).

Cyanide and Cellular Respiration

  • Cyanide poisons the electron transport chain.
  • Terminates the ability to generate ATP aerobically.
  • Elevated lactic acid levels postmortem.
  • Venous oxygen saturation is greater than 90%.

Exercise Metabolism Goals

  • Mobilize free fatty acids.
  • Decrease glucose uptake in non-working muscles.
  • Provide glucose for the nervous system.
  • Increase breakdown of liver and muscle glycogen.

Energy Continuum

  • ATP PC system: Predominates early (activities < 10 seconds).
  • Lactic anaerobic system: Predominates for activities around 2 minutes.
  • Aerobic system: Predominates for activities > 2 minutes.

Fuel Utilization

  • Fats: Dense energy source for prolonged periods.
  • Carbs: Readily available, but don't last as long.

ATP PC System

  • Immediate energy source.
  • Uses stored phosphocreatine.
  • PC stores supply about 10 seconds of all-out activity.
  • Replenishment: 50% in 30 seconds, complete in 3-5 minutes (passive recovery).
  • Trained individuals replenish PC stores faster than untrained.

Lactic Anaerobic System

  • Uses stored glycogen.
  • Fate of pyruvate dictates anaerobic glycolysis.
  • Low oxygen leads to lactic acid production.
  • Lasts up to roughly 2 minutes.
  • Muscle contraction and nervous system stimulates are triggers.

Mechanisms of Lactic Acid Production

  • Muscle contraction leads to glycogenolysis which is processed via anaerobic glycolysis.
  • Sympathetic nervous system stimulates epinephrine and glucagon release.
  • Enzymes- Lactate dehydrogenase (LDH) catalyst pyruvate conversion in lactic acid
  • Type ll muscle fibers stimulate an increased LDH activity, an increase in lactic acid production.

Lactic Acid Clearance

  • Oxidation (use it again).
  • Gluconeogenesis (non-carb sources).
  • Transamination (breakdown of amino acids).
  • Intracellular (within cell) and extracellular (between cell) mechanisms.

Intracellular Lactate Shuttle

  • MCT1 transports lactate from cytoplasm into mitochondria.
  • Lactate converts to pyruvate, enter glycolysis.

Extracellular Lactate Shuttle

  • MCT4 clears lactate from fast glycolytic fibers.
  • Transport into live for gluconeogenesis
  • Lactate is preferred fuel for cardiac muscle during exercise.

Fuel from Glucose

  • The primary and most easily utilized source og ATP production.

Glycogen

  • comes from either liver or muscle, gets broken down into glucose, phosphoglyceraldehyde, pyruvic acid, and acetyl CoA,

Proteins

  • Amino acids get broken down by oxidative deamination or transamination, main linker.

Triglycerides

  • Broken down into glycerol and our fatty acids, leading them to acetyl coenzyme A.

Lipolysis

  • Breakdown of stored fat.
  • Mediated by hormone-sensitive lipase (HSL).
  • HSL release triggered by increased glucagon, mediated by epinephrine, triggered by sympathetic nervous system.

Beta Oxidation

  • Breakdown of free fatty acids into acetyl coenzyme A.
  • Occurs in mitochondrial matrix with the presence of O2.
  • Five step five step process with 5 mechanisms.
  • Cycle through carbon bond which is broken

Palmitate Example (16-Carbon Fatty Acid)

  • Cycles through beta oxidation seven times.
  • Each cycle produces 1 FADH and 1 NADH+ (4 ATP yield).
  • 8 Acetyl CoA enzymes are yielded in this breakdown.
  • =106 net ATP from 16 C units.

Crossover Concept

  • At rest/lower intensity: Fat predominates.
  • Higher intensity: Carb contribution increases, decreased fat.

Protein Metabolism

  • Transamination: Transfer of amino group from amino acid to keto acid.
  • Oxidative Deamination: Amino group removed, becomes ammonia (toxic).
  • Gluconeogenesis: Alanine converted to glucose in liver.
  • Amino acid derivatives utilized as pyruvate or acetyl CoA.
  • Maintains blood glucose during prolonged aerobic exercise.
  • Trained individuals utilize ketones as fuel better.

Oxygen Deficit

  • At the onset of exercise, energy demand increases faster than oxygen supply.
  • Mechanisms:
    • Inertia of metabolism.
    • Inadequate initial oxygen supply.
  • Short-term light to moderate submaximal aeorbic exercise show that our aeorbic system predominates
  • Short-term high-intensity anaeribic exercise show that 02 is larget O2 Defciit.

EPOC (Excess Post-Exercise Oxygen Consumption)

  • Transition from exercise to rest.
  • Causes: ATP PC restoration, replenished O2 stores, elevated cardio-respiratroy function, hormones/body temp, lactate clear, substrate. shift to carbs/fat.
    * body temperature 60-70% oof contribition towards EPOC
    # Magnitude of increase factor intesnity over duration.

Lactate

*Baseline of 0.6-1.0

  • level is intensity over duration
  • Steady State, tells us that rate is being meet
  • High Lactates indicate that demand is not being met

Lactate Threshold

*Point on the Linear Cumlinar continumm
*Two Sharp rises on Lactate accumulation, also called Threshold 1,2

Lactate Threshold 1, (LT1)

*First noticeable rate, but effetivelly effectivel clear and retain areobic metabolism

Lactate Threshold 2, (LT2)

  • Second noticeable spike and greaty production than clears, anerobic production dominant

Oxygen Consumption (Aerobic Response)

  • Oxygen consumption plateau is when demand = supply

Oxygen Drift

  • Increase in use, even what the amount stays the same
  • workload is 0-70% VO2 Max capacity.
  • #5 mechanisms, high EP/NOREP increase in lactate accumulation in substrate utlitlizaation increased of ventilation, body tempt,

VO2

*Definied by maximum oxygen indiduals consume, transport and to prodcue ATP, Aerobicaly

Respiratroy Exchange Ratio (REE)

Def: Carbon Dioxide/ VO2 relationship.
*Lower Numbers show utlizesation of fats, hgiher numbers, utilization of carbon, 10-% fat with AER = 0.7.

Metabolic Adapations

  1. Sustrate fuel supply
  2. Enxyme Activity
    3 O2 ultiZATION
    4 Lactated Accumulation
  3. ATP prod, storage and turnover

Metabolic Adaapatations- Fuel and Enzyme Supply

With any sort Prolong adaeorpic training, any cardiovasular exercise/cardisivasula period of time witnes
1.Decrease Use of fuel.
2 Improve store glycogen. reserve to use. More effectivley to get to Beta 02 or get new glucose source
Enxzyme= improve acvtivity larger and and number activity greater cycilc through. Increase acticcy shuttle for efffectively

Metabilac adaaptions 02 Ultilatizatiion

  • impove VO2 MAx with lower deficit and oxygen and EPO
    *Decrease lactate due to enzyme capacity

Metabllic ADAPTATIONS- ATP

ATP is not better. In the same substrate increase size and number and capacity store larger size in much better turn over, can refill quickler

Detraining

*Factore that improve, decline. When stop Metabilocal decrease , if the not the same thing, the metabolica falter

  • Some reading to prompt and queriing further learning.