Kinesiology 203: Metabolism I Quiz

Kinesiology 203: Metabolism I

• Course: Kinesiology 203, Activity: Health, Fitness and Performance, Metabolism I: Anaerobic and aerobic energy pathways
• Instructor: Jenny Zhang, Faculty of Kinesiology
• Date: October 29, 2024

Objectives

• Students should understand factors controlling energy production rates.
• Students should know the contribution of each energy pathway during different exercise intensities and durations.
• Students should be able to describe the main energy pathways: immediate system, anaerobic glycolytic system, and aerobic/oxidative system (aerobic glycolysis, oxidative phosphorylation, and fat oxidation).

Recap: Energy Transfer in the Body

• Chemical bonds in macronutrients (carbohydrates, lipids, proteins) in food are a form of potential energy.
• These chemical bonds are relatively weak and not directly usable in the body.
• The body converts these to high-energy compounds (ATP).
• ATP is the body's primary energy currency.
• Energy transfer results in chemical waste (CO2, H2O), heat, and kinetic energy (motion).
• Energy is needed for growth, repair, and cellular/nerve functions.

Summary: Metabolic Energy Pathways

• Detailed diagram depicting complex biochemical pathways involving enzymes, substrates, products, and locations (cytosol, mitochondria) within a cell.
• Glycolysis, fatty acid oxidation, Krebs cycle, electron transport chain (ETC).

Immediate System (ATP-PCr System)

• The immediate system uses stored ATP and phosphocreatine (PCr).
• It's the fastest and simplest energy system.
• It doesn't require oxygen for its function.
• The breakdown of PCr releases 10.3 kcal/per mol, enough for ~8-13 seconds of maximal effort.
• PCr breakdown depends on exercise intensity.

Anaerobic Glycolytic Pathway

• Breakdown of glucose or glycogen to produce lactate.
• Glycolysis produces 2 ATP; glycogenolysis produces 3 ATP.
• Anaerobic glycolysis predominates during the first 1-2 minutes of high-intensity exercise.
• Doesn't require oxygen.
• Carbohydrate is the only macronutrient that can generate ATP anaerobically.
• Limitations: produces fewer ATP compared to aerobic pathways, produces H+ ions that reduce blood/muscle pH, leading to muscle fatigue.
• Lactate is a fuel that can be converted back to glucose.

Aerobic/Oxidative System

• Involves three main processes: aerobic glycolysis, Krebs cycle/Citric acid cycle, and electron transport chain, all inside mitochondria.
• Requires oxygen for its function, also known as cellular respiration.
• Aerobic capacity of a muscle determined by the number and density of mitochondria and is optimized when capillaries are dense near those mitochondria.
• Aerobic pathways produce a significant amount of ATP.
• Pyruvate is converted to acetyl-CoA in mitochondria.
• Acetyl-CoA enters the Krebs cycle.
• NADH and FADH2 generated in Krebs enter the electron transport chain to generate ATP.

ATP Yield from Aerobic Glycolysis

• 1 NADH + H+ = 2.5 ATP.
• 1 FADH2 = 1.5 ATP.
• Glycolysis prior to mitochondria yields 2 ATP.
• 4 NADH from glycolysis equals 10 ATP.
• Krebs cycle produces 2 ATP.
• Oxidative phosphorylation from the remaining 6 NADH and 2 FADH2 creates 15 ATP and 3 ATP, respectively, for a total yield of 30 ATP + 2 ATP + 2 ATP + 4 ATP = 40 ATP.

Intro to Fat Oxidation

• Aerobic glycolysis and fat oxidation both enter the Krebs cycle, and a cell must decide how to use them.
• Variables considered by a cell include current nutrient availability and exercise intensity.