chapter 3 energy metabolism and metabolic adaptations to training
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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.