Energy Metabolism in Nutrition for Sport & Exercise

These flashcards summarize key terms and concepts related to energy metabolism, focusing on processes relevant to nutrition for sport and exercise.

ATP Production: Glycolysis

$2-3$ ATP/mol of glucose.

ATP Production: Carbohydrate Oxidation

Approximately $38-39$ ATP/mol of glucose.

ATP Production: Fat Oxidation

$100+$ ATP/mol of fatty acid.

ATP Production: Protein Oxidation

$25-30$ ATP

ATP (Adenosine Tri-phosphate)

The key energy molecule in cells, synthesized from food to provide energy for cellular functions.

Components of ATP

Adenine, Ribose, and Three Phosphate groups (P-P-P).

ATP-ADP Cycle

A process where ATP converts to ADP (Adenosine Diphosphate) by releasing one phosphate group, releasing energy for cellular work. Energy is absorbed when ADP is re-phosphorylated back to ATP.

Major Fuel Sources for Energy Metabolism

Carbohydrates, Fat, Protein, and Phosphate (as in creatine phosphate).

Glycogen Storage in Liver

Approximately 80-100 grams of glycogen.

Triglycerides (TGs) Storage in Adipose Tissue

More than 11,000 grams of triglycerides.

Fuel Stores in Muscle

Glycogen, ATP, Creatine Phosphate (CP), and Intramuscular Triglycerides (IMTGs).

Liver Glycogen Energy Availability

380 kcal, lasting approximately $\sim 20$ minutes.

Muscle Glycogen Energy Availability

$\sim 1500$ kcal, lasting approximately $\sim 80$ minutes.

Types of Energy Systems

Anaerobic Systems (high intensity) including Creatine Phosphate System and Anaerobic Glycolysis; and Aerobic Systems (low intensity) including Oxidative Phosphorylation.

Creatine Phosphate System Characteristics

Very fast speed of action, very small amount of ATP replenished, very short duration of action.

Anaerobic Glycolysis Characteristics

Fast speed of action, small amount of ATP replenished, short duration of action.

Oxidative Phosphorylation Characteristics

Very slow speed of action, large amount of ATP replenished, very long duration of action.

PCr breakdown (Max Rate of ATP Resynthesis)

$2.25$ mmol ATP/kg w.w./s

Glycolysis (Max Rate of ATP Resynthesis)

$1.10$ mmol ATP/kg w.w./s

Enzyme Regulation in Energy Release

Enzymes speed up reactions and lower activation energy, facilitating ATP resynthesis.

Creatine Phosphate System Overview

Duration: $0-10$ seconds at $90-100\%$ intensity. Active at the start of all exercise, occurs in the cytosol.

Creatine Phosphate System Central Components

ATP, creatine phosphate (CP), ATPase, and creatine kinase (CK).

Creatine Phosphate System Regulation

Increased ADP levels lead to increased CK rate; decreased ADP levels lead to decreased CK rate.

CP Depletion and Repletion

CP can drop $\sim 70\%$ within $6$ seconds of exhaustive exercise. Repletion occurs with rest: $1-2$ minutes for $\sim 70\%$ CP replenishment; $30$ seconds for $50-70\%$ ATP replenishment.

Adenylate Kinase System Equation

ADP + ADP $\rightleftharpoons$ ATP + AMP. Also known as the bridge system that stimulates glycolysis.

Anaerobic Glycolysis Overview

Duration: $30-90$ seconds at $75-90\%$ intensity. Involves $9$ chemical reactions occurring in the cytosol, primarily utilizing carbohydrates.

Lactate and Muscle Fatigue

Lactate is a by-product of anaerobic glycolysis and DOES NOT cause fatigue or muscle soreness. It is associated with muscle recovery.

Glycogen Cycle During High-Intensity Exercise

Glycogen can be fully depleted during intense exercise and is replenished by consuming carbohydrates ('CARB LOAD HARDER').

Oxidative Phosphorylation Overview

Duration: More than $2-3$ minutes, using oxygen to generate ATP. Occurs in the mitochondria and utilizes carbohydrates, fats, and proteins.

Carbohydrate Oxidation Pathway

Krebs Cycle $\to$ Glycolysis $\to$ Electron Transport Chain (ETC).

Fat Oxidation Pathway

Lipolysis $\to$ Beta-Oxidation $\to$ Krebs Cycle $\to$ ETC.

Protein Oxidation Overview

Involves proteolysis and subsequent entry into the Krebs cycle and ETC for energy production.

ATP Produced by Creatine Phosphate

1 ATP/mol.

ATP Produced by Glycolysis

2-3 ATP/mol of glucose.

ATP Produced by Carbohydrate Oxidation

$\sim 38-39$ ATP/mol of glucose.

ATP Produced by Fat Oxidation

100+ ATP/mol of fatty acid.

ATP Produced by Protein Oxidation

25-30 ATP/mol of amino acid.

Interactive Contributions of Energy Systems

All energy systems are active simultaneously, but their contribution varies based on exercise intensity and duration.