Unit 2: Ingestion to Energy Metabolism

Vocabulary flashcards covering ATP, energy systems (phosphagen, anaerobic, aerobic), macronutrient pathways (glycolysis, beta-oxidation, gluconeogenesis), and stored energy forms as presented in Unit 2: Ingestion to Energy Metabolism.

Adenosine Triphosphate (ATP)

The main chemical energy currency of the body; powered by high-energy phosphate bonds to drive cellular processes.

Phosphagen Energy System

Immediate-energy system lasting about 20–30 seconds of high-intensity activity; uses stored ATP and phosphocreatine (CrP) in muscle.

Creatine Phosphate (Phosphocreatine)

A stored high-energy phosphate compound in muscle that donates phosphate to ADP to rapidly regenerate ATP during short, intense efforts.

Anaerobic Energy System

Rapid ATP production via glycolysis without the need for oxygen; supports roughly up to 2 minutes of high-intensity activity and produces lactate.

Aerobic Energy System

Oxygen-using energy system that metabolizes fats, carbohydrates (and some proteins) to acetyl-CoA and through the citric acid cycle and electron transport chain to produce ATP for long-duration activity.

Glycolysis

Metabolic pathway that breaks down glucose to pyruvate (or lactate under anaerobic conditions), yielding ATP and NADH.

Lactate

Byproduct of anaerobic glycolysis when pyruvate is reduced to lactate; can accumulate during high-intensity effort and can be used as an energy source in some tissues.

Glycogen

Stored form of glucose in liver and muscle, mobilized to fuel exercise.

Triglycerides

Stored fats in adipose tissue; breakdown provides fatty acids for energy production.

Beta-oxidation

Process by which fatty acids are broken down in mitochondria to acetyl-CoA for entry into the citric acid cycle.

Acetyl-CoA

Central metabolic molecule derived from carbohydrates, fats, and proteins that enters the citric acid cycle to generate energy.

Citric Acid Cycle (Krebs Cycle)

Aerobic pathway in mitochondria that oxidizes acetyl-CoA to CO2, generating NADH and FADH2 for ATP production.

Electron Transport Chain (ETC)

Final stage of aerobic respiration where NADH and FADH2 donate electrons to generate ATP; requires oxygen.

Pyruvate

End product of glycolysis; can become acetyl-CoA in the presence of oxygen or be converted to lactate under anaerobic conditions.

Gluconeogenesis

Metabolic pathway that forms glucose from non-carbohydrate sources, including certain amino acids; helps maintain blood glucose during exercise.

Protein as an energy source

Proteins can be broken down for energy (usually <5% during exercise) or converted to glucose via gluconeogenesis.

Stored energy forms

The body's energy reserves: triglycerides (fats), glycogen (carbohydrates), and protein (a last-resort energy source).

ADP to ATP

Conversion of ADP to ATP via free phosphate and energy from phosphocreatine or cellular processes to rapidly replenish ATP.

Carbohydrate intake during exercise

Recommendation: consume about 30–60 g of carbohydrates every 60–90 minutes of exercise to maintain energy and spare glycogen.