Chapter 3 Energy Metabolism andMetabolic Adaptations to

Training

Key Concepts

• adenosine triphosphate- phosphocreatine (ATP-PC) system

• aerobic• allosteric inhibition• anabolism• anaerobic• anaerobic

glycolysis

• beta-oxidation• carbohydrate-

sparing effect• catabolism• dehydrogenase

enzymes• electron transport

system (ETS)• energy

metabolism

• enzyme• glycogenolysis• Krebs cycle• lactic acid• Law of Mass

Action• lock and key work

method• myoglobin

• phosphatase• phosphocreatine

(PC)• phosphofructokina

se (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 andoxygen 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 reactantto which they bind. The enzyme must fitprecisely with the reactant to catalyze thereaction.

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. ATP ADP + inorganic

phosphate (Pi) + energy

2. PC + ADP ATP + 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 dehydrogenase1, 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 inmetabolism?• 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:

pyruvatepyruvate dehydrogenase complexacetyl coenzyme A

isocitrateisocitrate dehydrogenasealpha-ketoglutarate

alpha-ketoglutaratealpha-ketoglutarate dehydrogenasesuccinyl coenzyme A

malatemalate dehydrogenaseoxaloacetate

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 FADH2

oxidized?

Coenzyme Q

Where in the ETS is NADH + H+ oxidized?

Flavoprotein

How many ATP can be produced in the ETS system from one FADH2?

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?

C6H12O6 + 6O2 + 38ADP + 38P 6CO2 + 6H20 + 38ATP

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 enzymesCK and AK in the ATP-PC system and the

glycolytic enzyme PFK

increase PFK butnot CK and AK

Useful Websites

Biological Energy Conversion, Review of Anaerobic Metabolismwww.life.uiuc.edu/crofts/bioph354/lect2.html

Electron Transport System

http://faculty.nl.edu/jste/electron_transport_system.htm

Cycling Performance Tips, basic physiology, cell energy metabolismwww.halcyon.com/gasman/bscphys.htm

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.