Oxidative System and Substrate Metabolism

Vocabulary practice flashcards covering the oxidative energy system, anaerobic glycolysis, beta oxidation, the citric acid cycle, the electron transport chain, and substrate storage capacities.

Anaerobic Glycolysis

The metabolic process occurring in the sarcoplasm that breaks down glucose into $2$ pyruvate molecules, yielding a net of $2$ ATP.

Anaerobic Glycogenolysis

The metabolic breakdown of intramuscular glycogen into $2$ pyruvate molecules in the sarcoplasm, producing a net yield of $3$ ATP.

Sarcoplasmic Pyruvate Inhibition

The inhibitory effect where an accumulation of pyruvate in the sarcoplasm halts the enzymatic conversion of glucose to glucose 6-phosphate and glycogen to glucose 1-phosphate.

Anaerobic Fate of Pyruvate

The biochemical pathway occurring in the absence of oxygen ($O_2$) where pyruvate is converted in the sarcoplasm into $2\text{ lactate} + 2H^+$.

Aerobic Fate of Pyruvate

The pathway occurring in the presence of oxygen ($O_2$) whereby pyruvate is transported into the mitochondria to undergo oxidative metabolism.

Pyruvate Dehydrogenase Complex

The multienzyme complex responsible for converting pyruvate into acetyl-CoA, bridging anaerobic glycolysis to the citric acid cycle.

Hormone Sensitive Lipase

The enzyme in adipose tissue that catabolizes triglycerides into free fatty acids (FFAs) and glycerol.

Carnitine Acyl Transporter

The transport mechanism that shuttles fatty acyl-CoA across the mitochondrial membrane into the mitochondrion for beta-oxidation.

Beta Oxidation

The mitochondrial catabolic pathway that breaks down free fatty acids (as fatty acyl-CoA) into acetyl-CoA, simultaneously generating reduced co-enzymes NADH and $FADH_2$.

Citric Acid Cycle

A series of cyclic mitochondrial reactions (also termed the Krebs cycle or tricarboxylic acid cycle) that oxidize acetyl-CoA, directly generating $1 \times \text{ATP}$, releasing $CO_2$, and producing $3 \times \text{NADH}$ and $1 \times FADH_2$ per turn.

Key Regulatory Enzymes of the Citric Acid Cycle

The three primary regulatory enzymes of the citric acid cycle: 1) citrate synthase, 2) isocitrate dehydrogenase, and 3) $\alpha$-ketoglutarate dehydrogenase.

Nicotinamide Adenine Dinucleotide (NAD)

A metabolic co-enzyme that accepts hydrogen ions ($H^+$) and electrons from glycolysis, beta oxidation, and the citric acid cycle to form NADH, which transports them to the electron transport chain.

Flavin Adenine Dinucleotide (FAD)

A metabolic co-enzyme that binds hydrogen atoms during catabolism to form $FADH_2$, which supplies electrons directly to the electron transport chain.

Electron Transport Chain (ETC)

A series of $5$ protein structures embedded within the inner mitochondrial membrane that pass electrons delivered by NADH and $FADH_2$ along to oxygen ($O_2$).

Terminal Reaction of the Electron Transport Chain

The reaction at the end of the electron transport chain where oxygen binds electrons and hydrogen ions to synthesize water: $O_2 + 4e^- + 4H^+ \rightarrow 2H_2O$.

Protein Metabolism in Exercise

The pathway in which amino acids undergo transamination and deamination to form ammonia, urea, and urine; it provides only a minimal or limited contribution to energy provision during exercise in a normal nutritional state.

Muscle Glycogen Storage

An endogenous carbohydrate store providing approximately $400\,g$ of substrate and $1\,640\,kCal$ of energy, representing an approximate running capacity of $175\,min$ for an $80\,kg$ individual.

Liver Glycogen Storage

An endogenous carbohydrate reserve providing approximately $100\,g$ of substrate and $410\,kCal$ of energy, yielding roughly $44\,min$ of running capacity for an $80\,kg$ individual.

Adipose Tissue Triglycerides Storage

The body's primary lipid reserve, providing approximately $12\,000\,g$ of substrate and $112\,800\,kCal$ of energy, equivalent to roughly $12\,045\,min$ of running capacity for an $80\,kg$ individual with $15\%$ body fat.

Intramuscular Triglycerides Storage

Lipid stores located within skeletal muscle totaling approximately $300\,g$ of substrate and $2\,820\,kCal$ of energy, providing an estimated running capacity of $301\,min$ for an $80\,kg$ individual.

Hierarchy of ATP Provision Rate

The comparative order of energy systems by speed of ATP generation, where Stored ATP and ATP–PCr deliver the highest rate of provision, followed by the Glycolytic System, and lastly the Oxidative System.