Metabolism Part I: Anaerobic Energy Systems - Vocabulary Flashcards

A set of vocabulary-style flashcards covering key terms and definitions from the notes on anaerobic energy systems.

Metabolism

The sum of all chemical processes in living organisms that convert food into energy and building blocks for life.

Energy

The capacity to perform work.

Forms of energy

Chemical, electrical, thermal, mechanical, radiant, and nuclear energy.

First Law of Thermodynamics

Energy cannot be created or destroyed; it can only be transformed from one form to another.

Exergonic

Energy-releasing chemical reactions.

Endergonic

Energy-requiring chemical reactions.

Macronutrients

Carbohydrates, fats, and proteins—the main energy sources in the diet.

ATP

Adenosine Triphosphate; the chemical energy currency directly used by cells.

Phosphocreatine (PCr)

A high-energy phosphate store that rapidly regenerates ATP via creatine kinase.

ATP-PCr system

The fastest energy system, replenishing ATP during very short, high-intensity efforts using PCr.

Glycolysis

The breakdown of glucose or glycogen to pyruvate (and lactate under anaerobic conditions), yielding a net 2–3 ATP per substrate.

Oxidative system

The aerobic energy system that uses oxygen to generate ATP from carbohydrates, fats, and proteins over longer time.

Glucose

A monosaccharide; the primary circulating form of sugar used by body tissues.

Glycogen

Stored glucose in liver and skeletal muscle.

Glycogenesis

The formation of glycogen from glucose for storage.

Glycogenolysis

The breakdown of glycogen to release glucose.

Lipids

Fats; energy-dense molecules stored as triglycerides.

Triglycerides

Glycerol bound to three fatty acids; the main storage form of fat.

Free fatty acids (FFAs)

Fatty acids released from triglycerides and used to generate ATP.

Energy density

Energy per gram: fat ≈ 9 kcal/g; carbohydrates ≈ 4 kcal/g.

Lactate

Conjugate base of lactic acid produced during glycolysis; can be used as fuel or converted to glucose.

Lactate dehydrogenase (LDH)

Enzyme that converts pyruvate to lactate during anaerobic glycolysis.

Aerobic metabolism

Metabolism that uses oxygen to produce ATP; typically sustaining activity over time.

Anaerobic metabolism

Metabolism that does not require oxygen; relies on PCr and glycolysis for ATP.

Hexokinase

Enzyme that phosphorylates glucose to glucose-6-phosphate, consuming one ATP in glycolysis.

Phosphofructokinase (PFK)

Rate-limiting enzyme of glycolysis; converts fructose-6-phosphate to fructose-1,6-bisphosphate, consuming ATP.

Pyruvate kinase

Enzyme that converts phosphoenolpyruvate to pyruvate, producing ATP (payoff step).

3-phosphoglycerate kinase

Glycolytic enzyme that participates in ATP production during the payoff phase.

Creatine kinase

Enzyme that transfers a phosphate from PCr to ADP to form ATP.

ATPase

Enzyme that hydrolyzes ATP to ADP and Pi, releasing usable energy (≈7.6 kcal/mol).

Glycolysis payoff phase

Part of glycolysis where ATP is produced; net gain is 2 ATP (or 3 with glycogen as substrate).

ATP stores

ATP stores are very limited in the body (roughly about 1 kcal) and must be continually replenished.

PCr replenishment time

PCr can be substantially replenished in 3–5 minutes; full restoration takes about 10 minutes.

Lactate shuttle

Transport of lactate from active muscle to other tissues (heart, liver, brain) for oxidation or gluconeogenesis.