Chapter 3 Energy Metabolism and Metabolic Adaptations to Training

Key Concepts

adenosine triphosphate- phosphocreatine (ATP-PC) systemadenosine triphosphate- phosphocreatine (ATP-PC) system aerobic allosteric inhibition anabolism anaerobic anaerobic glycolysis beta-oxidation carbohydrate- sparing effectcarbohydrate- sparing effect catabolism dehydrogenase enzymesdehydrogenase enzymes electron transport system (ETS)electron transport system (ETS) energy metabolism

enzyme glycogenolysis Krebs cycle lactic acid Law of Mass Action lock and key work methodlock and key work method myoglobin phosphatase phosphocreatine (PC)phosphocreatine (PC) phosphofructokinase (PFK)phosphofructokinase (PFK) phosphagen power triglyceride

Review Questions

Name four reasons physical educators, coaches, and exercise scientists have a basic understanding of energy metabolism. ATP is the source of energy for muscle contraction Producing enough ATP is essential to performance Adaptations to exercise training involve energy metabolism The metabolic demands of training are important in designing training or exercise prescriptions

What are anaerobic and aerobic metabolism? Aerobic metabolism is the –production of ATP with oxygen. Anaerobic metabolism is the –production of ATP without oxygen.

What is the respiratory chain? The Krebs cycle and the electron transport system (ETS), where ATP is produced and oxygen is utilized.

What are the three characteristics of enzymes? An enzyme speeds up or catalyzes a reaction. An enzyme is not changed by the reaction it causes. An enzyme does not change the result of the reaction.

What does it mean when we say that enzymes work by the lock-and-key method? The enzymes are specific to the reactant to which they bind. The enzyme must fit precisely with the reactant to catalyze the reaction.

What four factors affect the turnover rate of an enzyme? Temperature and pH of the cellular environment Concentration and activity of reactants and enzymes Allosteric inhibition Availability and concentrations of cofactors and coenzymes

What are the three primary enzymatic reactions that occur in the ATP-PC system? 1.ATPADP + inorganic phosphate (Pi) + energy 2.PC + ADPATP + C 3.2ADP ATP + AMP Myosin ATPase Creatine Kinase (CK) Adenylate Kinase (AK)

What is the net number of ATP produced during anaerobic glycolysis? 2 ATP molecules and 2 pyruvate molecules per molecule of glucose

What is anaerobic glycolysis? The primary system for ATP production for activities that last from approximately 20–30 seconds to two to three minutes The breakdown of glucose to lactate without the use of oxygen

Name the reactants, enzymes, and products for the two steps in glycolysis where ATP is produced. Step 1 –Reactant: –Enzyme: –Product: Step 2 –Reactant: – Enzyme: –Product: 1,3-biphosphoglycerate phosphoglycerate kinase (PGK) 3-phosphoglycerate phosphoenolpyruvate pyruvate kinase (PK) pyruvate

Name the reactants, enzymes, and products for the two steps in glycolysis where ATP is used. Step 1 –Reactant: –Enzyme: –Product: Step 2 –Reactant: –Enzyme: –Product: blood glucose hexokinase (HK) glucose-6-phosphate fructose-6-phosphate phosphofructokinase (PFK) fructose-1, 6-bisphosphate

Name the reactant, enzyme, and product for the step in glycolysis where NAD is reduced. Reactant: Enzyme: Product: glyceraldahyde 3-phosphate glyceraldahyde 3-phosphate dehydrogenase 1, 3-bisphosphoglycerate

Reactant: Enzyme: Product: Name the reactant, enzyme, and product for the step in glycolysis where NAD is oxidized. pyruvate lactate dehydrogenase Lactate

Name the rate-limiting enzyme in glycolysis. Phosphofructokinase (PFK) What is its significance in metabolism? It is the weak link—the rate of conversion of the reactant to product through enzymatic steps can proceed no faster than the rate- limiting enzyme will allow.

Within the cell’s mitochondria, what are the four steps where NAD is reduced during the aerobic metabolization of carbohydrates? Step 1 –Reactant: –Enzyme: –Product: Step 2 –Reactant: –Enzyme: –Product: Step 3 –Reactant: –Enzyme: –Product: Step 4 –Reactant: –Enzyme: –Product: pyruvate pyruvate dehydrogenase complex acetyl coenzyme A isocitrate isocitrate dehydrogenase alpha-ketoglutarate alpha-ketoglutarate dehydrogenase succinyl coenzyme A malate malate dehydrogenase oxaloacetate

Name the reactant, enzyme, and product for the step in the Kreb’s cycle where FAD is reduced. Reactant: Enzyme: Product: succinate succinate dehydrogenase fumarate

Name the reactant, enzyme, and product in the Kreb’s Cycle where ATP is produced. Reactant: Enzyme: Product: succinyl coenzyme A succinyl coenzyme A synthetase succinate

What is the electron transport system? The part of aerobic metabolism where 34 of the 38 ATP are produced

What is the final electron acceptor at the end of the ETS? Oxygen

Where in the ETS is FADH 2 oxidized? Coenzyme Q

Where in the ETS is NADH + H + oxidized? Flavoprotein

How many ATP can be produced in the ETS system from one FADH 2 ? 2 ATP

How many ATP can be produced in the ETS system from one NADH + H + ? 3 ATP

What is the net chemical reaction of the aerobic metabolism of glucose? C 6 H 12 O 6 + 6O ADP + 38P  6CO 2 + 6H ATP

Compare the power and capacity of the various energy production systems. The ATP-PC system –has low capacity because there is a limited store of phosphagens available. Carbohydrate oxidation –is limited by glycogen depletion. Fatty acid metabolism –has the greatest capacity because, under normal conditions, each person has an inexhaustible supply of energy-rich fats.

What are four main metabolic adaptations that result from endurance training? Increases myoglobin in skeletal muscle, which increases the amount of oxygen available to the mitochondria as the final electron acceptor at the end of ETS. Increases number and size of mitochondria within skeletal muscle, and increases levels of enzymes within the mitochondria and the beta oxidation of long-chain fatty acids. Increases alanine transaminase, so that a greater proportion of pyruvate is converted to alanine than to lactate. Glycolytic process is not limiting. An increase in the use of fatty acids compared to carbohydrates for ATP production.

What are the effects of sprint training on anaerobic metabolism? Increases the enzymes PFK, LDH, and CK, which can improve performance by increasing the rate of ATP production. Increases phosphocreatine stores within the muscle, which allows high-intensity exercise to be maintained for a longer period of time before fatigue.

What are the metabolic effects of resistance training? Increases ATP and phosphocreatine stores within the muscle In general, improves ATP availability and leads to greater muscle strength and an enhanced ability to perform repeated muscle contractions Name those specific to the type of program programs involving more repetitions programs involving fewer repetitions increase enzymes CK and AK in the ATP-PC system and the glycolytic enzyme PFK increase PFK but not CK and AK

Useful Websites

Biological Energy Conversion, Review of Anaerobic Metabolism Electron Transport System system.htm Cycling Performance Tips, basic physiology, cell energy metabolism

Selected Images

Figure 3.1 Fat, carbohydrate, and protein can be used to produce ATP aerobically.

Figure 3.2 Anaerobic glycolysis involves the breakdown of glucose to lactate.

Figure 3.3 The Krebs cycle occurs within the mitochondria of the muscle fiber.

Figure 3.4 Most ATP is produced in the electron transport system.

Figure 3.5 Anaerobic breakdown of glucose results in the net production of only 2 ATP, while aerobic metabolism nets 38 ATP.