fisiologi senam bioenergetics

Scott K. Powers • Edward T. HowleyScott K. Powers • Edward T. HowleyScott K. Powers • Edward T. HowleyScott K. Powers • Edward T. Howley

Theory and Application to Fitness and PerformanceTheory and Application to Fitness and PerformanceSEVENTH EDITION

Chapter

Presentation prepared by:

Brian B. Parr, Ph.D.

University of South Carolina AikenCopyright ©2009 The McGraw-Hill Companies, Inc. Permission required for reproduction or display outside of classroom use.

Bioenergetics

Chapter 3

Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved.

Objectives

1. Discuss the functions of the cell membrane, nucleus, and mitochondria.

2. Define the following terms: (1) endergonic reactions, (2) exergonic reactions, (3) coupled reactions, and (4) bioenergetics.

3. Describe the role of enzymes as catalysts in cellular chemical reactions.

4. List and discuss the nutrients that are used as fuels during exercise.

5. Identify the high-energy phosphates.

Chapter 3


Objectives

6. Discuss the biochemical pathways involved in anaerobic ATP production.

7. Discuss the aerobic production of ATP.

8. Describe the general scheme used to regulate metabolic pathways involved in bioenergetics.

9. Discuss the interaction between aerobic and anaerobic ATP production during exercise.

10. Identify the enzymes that are considered rate limiting in glycolysis and the Krebs cycle.

Chapter 3


Outline

Cell Structure Biological Energy

TransformationCellular Chemical Reactions

Oxidation-Reduction Reactions

Enzymes

Fuels for ExerciseCarbohydrates

Fats

Proteins

High-Energy Phosphates

BioenergeticsAnaerobic ATP ProductionAerobic ATP production

Aerobic ATP Tally Efficiency of Oxidative

Phosphorylation

Control of Bioenergetics

Control of ATP-PC System

Control of GlycolysisControl of Krebs Cycle

and Electron Transport Chain

Interaction Between Aerobic/Anaerobic ATP Production

Chapter 3


Introduction

• Metabolism – Sum of all chemical reactions that occur in the body– Anabolic reactions

Synthesis of molecules

– Catabolic reactions Breakdown of molecules

• Bioenergetics– Converting foodstuffs (fats, proteins, carbohydrates)

into energy

Chapter 3


Cell Structure

Cell Structure

• Cell membrane– Semipermeable membrane that separates the cell

from the extracellular environment• Nucleus

– Contains genes that regulate protein synthesis Molecular biology

• Cytoplasm– Fluid portion of cell– Contains organelles

Mitochondria

Chapter 3


Cell Structure

A Typical Cell and Its Major Organelles

Figure 3.1

Chapter 3


In Summary

Metabolism is defined as the total of all cellular reactions that occur in the body; this includes both the synthesis of molecules and the breakdown of molecules.

Cell structure includes the following three major parts: (1) cell membrane, (2) nucleus, and (3) cytoplasm (called sarcoplasm in muscle).

The cell membrane provides a protective barrier between the interior of the cell and the extracellular fluid.

Genes (located within the nucleus) regulate protein synthesis within the cell.

The cytoplasm is the fluid portion of the cell and contains numerous organelles

Cell Structure

Chapter 3


A Closer Look 3.1Molecular Biology and Exercise Science

• Study of molecular structures and events underlying biological processes– Relationship between genes and cellular

characteristics they control• Genes code for specific cellular proteins

– Process of protein synthesis• Exercise training results in modifications in protein

synthesis– Strength training results in increased synthesis of

muscle contractile protein• Molecular biology provides “tools” for

understanding the cellular response to exercise

Cell Structure

Chapter 3


Steps Leading to Protein Synthesis

Figure 3.2

1. DNA contains information to produce proteins.

2. Transcription produces mRNA.

3. mRNA leaves nucleus and binds to ribosome.

4. Amino acids are carried to the ribosome by tRNA.

5. In translation, mRNA is used to determine the arrangement of amino acids in the polypeptide chain.

Biological Energy Transformation

Chapter 3



Cellular Chemical Reactions

• Endergonic reactions– Require energy to be added – Endothermic

• Exergonic reactions– Release energy – Exothermic

• Coupled reactions– Liberation of energy in an exergonic reaction drives

an endergonic reaction

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The Breakdown of Glucose: An Exergonic Reaction

Figure 3.3


Chapter 3



Figure 3.4

The energy given off by the exergonic reaction powers the endergonic reaction

Coupled Reactions

Chapter 3


Oxidation-Reduction Reactions

• Oxidation – Removing an electron

• Reduction – Addition of an electron

• Oxidation and reduction are always coupled reactions

• Often involves the transfer of hydrogen atoms rather than free electrons– Hydrogen atom contains one electron– A molecule that loses a hydrogen also loses an

electron and therefore is oxidized• Importance of NAD and FAD


Chapter 3


Oxidation-Reduction Reaction Involving NAD and NADH


Figure 3.5

Chapter 3


Enzymes

• Catalysts that regulate the speed of reactions– Lower the energy of activation

• Factors that regulate enzyme activity– Temperature– pH

• Interact with specific substrates– Lock and key model


Chapter 3


Enzymes Catalyze Reactions


Figure 3.6

Enzymes lower the energy of activation

Chapter 3


The Lock-and-Key Model of Enzyme Action

Figure 3.7

a) Substrate (sucrose) approaches the active site on the enzyme.

b) Substrate fits into the active site, forming enzyme-substrate complex.

c) The enzyme releases the products (glucose and fructose).


Chapter 3


Clinical Applications 3.1Diagnostic Value of Measuring Enzyme Activity in the Blood


• Damaged cells release enzymes into the blood– Enzyme levels in blood indicate disease or tissue

damage• Diagnostic application

– Elevated lactate dehydogenase or creatine kinase in the blood may indicate a myocardial infarction

Chapter 3


Examples of the Diagnostic Value of Enzymes in Blood


Chapter 3



Classification of Enzymes

• Oxidoreductases– Catalyze oxidation-reduction reactions

• Transferases– Transfer elements of one molecule to another

• Hydrolases– Cleave bonds by adding water

• Lyases– Groups of elements are removed to form a double bond or

added to a double bond• Isomerases

– Rearrangement of the structure of molecules• Ligases

– Catalyze bond formation between substrate molecules

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Example of the Major Classes of Enzymes


Chapter 3


Factors That Alter Enzyme Activity

• Temperature– Small rise in body temperature increases enzyme

activity– Exercise results in increased body temperature

• pH– Changes in pH reduces enzyme activity– Lactic acid produced during exercise


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The Effect of Body Temperature on Enzyme Activity


Figure 3.8

Chapter 3


The Effect of pH on Enzyme Activity


Figure 3.9

Chapter 3


Carbohydrates

• Glucose– Blood sugar

• Glycogen – Storage form of glucose in liver and muscle

Synthesized by enzyme glycogen synthase

– Glycogenolysis Breakdown of glycogen to glucose

Fuels for Exercise

Chapter 3


Fats

• Fatty acids– Primary type of fat used by the muscle– Triglycerides

Storage form of fat in muscle and adipose tissue Breaks down into glycerol and fatty acids

• Phospholipids– Not used as an energy source

• Steroids– Derived from cholesterol– Needed to synthesize sex hormones

Fuels for Exercise

Chapter 3


Fuels for Exercise

Protein

• Composed of amino acids• Some can be converted to glucose in the liver

– Gluconeogenesis• Others can be converted to metabolic intermediates

– Contribute as a fuel in muscle• Overall, protein is not a primary energy source

during exercise

Chapter 3


In Summary

The body uses carbohydrate, fat, and protein nutrients consumed daily to provide the necessary energy to maintain cellular activities both at rest and during exercise. During exercise, the primary nutrients used for energy are fats and carbohydrates, with protein contributing a relatively small amount of the total energy used.

Glucose is stored in animal cells as a polysaccharide called glycogen.

Fatty acids are the primary form of fat used as an energy source in cells. Fatty acids are stored as triglycerides in muscle and fat cells.

Fuels for Exercise

Chapter 3


• Adenosine triphosphate (ATP)– Consists of adenine, ribose, and three linked

phosphates• Synthesis

• Breakdown

ADP + Pi ATP

ADP + Pi + EnergyATP ATPase



Chapter 3


Structure of ATP


Figure 3.10

Chapter 3


Model of ATP as the Universal Energy Donor

Figure 3.11


Chapter 3


Bioenergetics

• Formation of ATP – Phosphocreatine (PC) breakdown– Degradation of glucose and glycogen

Glycolysis

– Oxidative formation of ATP• Anaerobic pathways

– Do not involve O2

– PC breakdown and glycolysis• Aerobic pathways

– Require O2

– Oxidative phosphorylation

Bioenergetics

Chapter 3


ATP + CPC + ADPCreatine kinase

Anaerobic ATP Production

• ATP-PC system– Immediate source of ATP

• Glycolysis– Glucose 2 pyruvic acid or 2 lactic acid – Energy investment phase

Requires 2 ATP

– Energy generation phase Produces 4 ATP, 2 NADH, and 2 pyruvate or 2 lactate

Bioenergetics

Chapter 3


The Winning Edge 3.1Does Creatine Supplementation Improve Exercise Performance?• Depletion of PC may limit short-term, high-intensity

exercise• Creatine monohydrate supplementation

– Increased muscle PC stores– Some studies show improved performance in short-

term, high-intensity exercise Inconsistent results may be due to water retention and

weight gain

– Increased strength and fat-free mass with resistance training

• Creatine supplementation does not appear to pose health risks

Bioenergetics

Chapter 3


A Closer Look 3.2Lactic Acid or Lactate?

• Terms lactic acid and lactate used interchangeably– Lactate is the conjugate base of lactic acid

• Lactic acid is produced in glycolysis– Rapidly disassociates to lactate and H+

Figure 3.12

The ionization of lactic acid forms the conjugate base called lactate

Bioenergetics

Chapter 3


The Two Phases of Glycolysis

Figure 3.13

Bioenergetics

Chapter 3


Interaction Between Blood Glucose and Muscle Glycogen in Glycolysis

Figure 3.14

Bioenergetics

Chapter 3


Bioenergetics

Figure 3.15

Glycolysis: Energy Investment Phase

Chapter 3


Glycolysis: Energy Generation Phase

Bioenergetics

Figure 3.15

Chapter 3


• Transport hydrogens and associated electrons– To mitochondria for ATP generation (aerobic)– To convert pyruvic acid to lactic acid (anaerobic)

• Nicotinamide adenine dinucleotide (NAD)

• Flavin adenine dinucleotide (FAD)

NAD + 2H+ NADH + H+

FAD + 2H+ FADH2

Hydrogen and Electron Carrier Molecules

Bioenergetics

Chapter 3


A Closer Look 3.3NADH is “Shuttled” into Mitochondria

• NADH produced in glycolysis must be converted back to NAD– By converting pyruvic acid to lactic acid– By “shuttling” H+ into the mitochondria

• A specific transport system shuttles H+ across the mitochondrial membrane– Located in the mitochondrial membrane

Bioenergetics

Chapter 3


Conversion of Pyruvic Acid to Lactic Acid

Figure 3.16

The addition of two H+ to pyruvic acid forms NAD and lactic acid

Bioenergetics

Chapter 3


The immediate source of energy for muscular contraction is the high-energy phosphate ATP. ATP is degraded via the enzyme ATPase as follows:

Formation of ATP without the use of O2 is termed anaerobic metabolism. In contrast, the production of ATP using O2 as the final electron acceptor is referred to as aerobic metabolism.

In Summary

ADP + Pi + EnergyATP ATPase

Bioenergetics

Chapter 3


Exercising skeletal muscles produce lactic acid. However, once produced in the body, lactic acid is rapidly converted to its conjugate base, lactate.

Muscle cells can produce ATP by any one or a combination of three metabolic pathways: (1) ATP-PC system, (2) glycolysis, (3) oxidative ATP production.

The ATP-PC system and glycolysis are two anaerobic metabolic pathways that are capable of producing ATP without O2.

In Summary

Bioenergetics

Chapter 3


Bioenergetics

Aerobic ATP Production

• Krebs cycle (citric acid cycle)– Pyruvic acid (3 C) is converted to acetyl-CoA (2 C)

CO2 is given off

– Acetyl-CoA combines with oxaloacetate (4 C) to form citrate (6 C)

– Citrate is metabolized to oxaloacetate Two CO2 molecules given off

– Produces three molecules of NADH and one FADH– Also forms one molecule of GTP

Produces one ATP

Chapter 3


The Three Stages of Oxidative Phosphorylation

Figure 3.17

Bioenergetics

Chapter 3


The Krebs Cycle

Figure 3.18

Bioenergetics

Chapter 3


Bioenergetics

Fats and Proteins in Aerobic Metabolism

• Fats– Triglycerides glycerol and fatty acids– Fatty acids acetyl-CoA

Beta-oxidation

– Glycerol is not an important muscle fuel during exercise

• Protein– Broken down into amino acids– Converted to glucose, pyruvic acid, acetyl-CoA, and

Krebs cycle intermediates

Chapter 3


Bioenergetics

Figure 3.19

Relationship Between the Metabolism of Proteins, Carbohydrates, and Fats

Chapter 3


Aerobic ATP Production

• Electron transport chain – Oxidative phosphorylation occurs in the

mitochondria– Electrons removed from NADH and FADH are

passed along a series of carriers (cytochromes) to produce ATP Each NADH produces 2.5 ATP Each FADH produces 1.5 ATP

– Called the chemiosmotic hypothesis– H+ from NADH and FADH are accepted by O2 to

form water

Bioenergetics

Chapter 3


Bioenergetics

The Chemiosmotic Hypothesis of ATP Formation

• Electron transport chain results in pumping of H+ ions across inner mitochondrial membrane– Results in H+ gradient across membrane

• Energy released to form ATP as H+ ions diffuse back across the membrane

Chapter 3


A Closer Look 3.4Beta Oxidation is the Process of Converting Fatty Acids to Acetyl-CoA• Breakdown of triglycerides releases fatty acids• Fatty acids must be converted to acetyl-CoA to be

used as a fuel– Activated fatty acid (fatty acyl-CoA) into

mitochondrion– Fatty acid “chopped” into 2 carbon fragments

forming acetyl-CoA• Acetyl-CoA enters Krebs cycle and is used for

energy

Bioenergetics

Chapter 3


Beta Oxidation

Figure 3.21

Bioenergetics

Chapter 3


Oxidative phosphorylation or aerobic ATP production occurs in the mitochondria as a result of a complex interaction between the Krebs cycle and the electron transport chain. The primary role of the Krebs cycle is to complete the oxidation of substrates and form NADH and FADH to enter the electron transport chain. The end result of the electron transport chain is the formation of ATP and water. Water is formed by oxygen-accepting electrons; hence, the reason we breathe oxygen is to use it as the final acceptor of electrons in aerobic metabolism.

In Summary

Bioenergetics

Chapter 3


A Closer Look 3.5A New Look at the ATP Balance Sheet

• Historically, 1 glucose produced 38 ATP• Recent research indicates that 1 glucose produces

32 ATP– Energy provided by NADH and FADH also used to

transport ATP out of mitochondria.– 3 H+ must pass through H+ channels to produce 1

ATP– Another H+ needed to move the ATP across the

mitochondrial membrane

Aerobic ATP Tally

Chapter 3


Metabolic Process High-Energy Products

ATP from Oxidative Phosphorylation

ATP Subtotal

Glycolysis 2 ATP 2 NADH

— 5

2 (if anaerobic) 7 (if aerobic)

Pyruvic acid to acetyl-CoA 2 NADH 5 12

Krebs cycle 2 GTP 6 NADH 2 FADH

— 15 3

14 29 32

Grand Total

32

Aerobic ATP Tally Per Glucose Molecule

Aerobic ATP Tally

Chapter 3


32 moles ATP/mole glucose x 7.3 kcal/mole ATP

686 kcal/mole glucosex 100 = 34%

Efficiency of Oxidative Phosphorylation


• One mole of ATP has energy yield of 7.3 kcal• 32 moles of ATP are formed from one mole of

glucose• Potential energy released from one mole of glucose

is 686 kcal/mole

• Overall efficiency of aerobic respiration is 34%– 66% of energy released as heat

Chapter 3


The aerobic metabolism of one molecule of glucose results in the production of 32 ATP molecules, whereas the aerobic yield for glycogen breakdown is 33 ATP.

The overall efficiency of aerobic of aerobic respiration is approximately 34%, with the remaining 66% of energy being released as heat.

In Summary


Chapter 3



• Rate-limiting enzymes– An enzyme that regulates the rate of a metabolic

pathway• Modulators of rate-limiting enzymes

– Levels of ATP and ADP+Pi

High levels of ATP inhibit ATP production Low levels of ATP and high levels of ADP+Pi stimulate ATP

production

– Calcium may stimulate aerobic ATP production


Chapter 3


Factors Known to Affect Rate-Limiting Enzymes

Pathway Rate-LimitingEnzyme

Stimulators Inhibitors

ATP-PC system Creatine kinase ADP ATP

Glycolysis Phosphofructokinase AMP, ADP, Pi, pH ATP, CP, citrate, pH

Krebs cycle Isocitratedehydrogenase

ADP, Ca++, NAD ATP, NADH

Electron transportchain

Cytochrome Oxidase ADP, Pi ATP


Chapter 3


Metabolism is regulated by enzymatic activity. An enzyme that regulates a metabolic pathway is termed a “rate-limiting” enzyme.

The rate-limiting enzyme for glycolysis is phosphofructokinase, while the rate-limiting enzymes for the Krebs cycle and electron transport chain are isocitrate dehydrogenase and cytochrome oxidase, respectively.

In general, cellular levels of ATP and ADP+Pi regulate the rate of metabolic pathways involved in the production of ATP. High levels of ATP inhibit further ATP production, while low levels of ATP and high levels of ADP+Pi stimulate ATP production. Evidence also exists that calcium may stimulate aerobic energy metabolism.

In Summary


Chapter 3



• Energy to perform exercise comes from an interaction between aerobic and anaerobic pathways

• Effect of duration and intensity– Short-term, high-intensity activities

Greater contribution of anaerobic energy systems

– Long-term, low to moderate-intensity exercise Majority of ATP produced from aerobic sources


Chapter 3



Figure 3.23

The Winning Edge 3.2Contribution of Aerobic/Anaerobic ATP Production During Sporting Events

Chapter 3


Energy to perform exercise comes from an interaction of anaerobic and aerobic pathways.

In general, the shorter the activity (high intensity), the greater the contribution of anaerobic energy production. In contrast, long-term activities (low to moderate intensity) utilize ATP produced from aerobic sources.

In Summary


Chapter 3


Study Questions

1. List and briefly discuss the functions of the three major components of cell structure.

2. Briefly explain the concept of coupled reactions.

3. Define the following terms: (1) bioenergetics, (2) endergonic reactions, and (3) exergonic reactions.

4. Discuss the role of enzymes as catalysts. What is meant by the expression “energy of activation”?

5. Where do glycolysis, the Krebs cycle, and oxidative phosphorylation take place in the cell?

6. Define the terms glycogen, glycogenolysis, and glycolysis.

Chapter 3


Study Questions

7. What are the high-energy phosphates? Explain the statement that “ATP is the universal energy donor.”

8. Define the terms aerobic and anaerobic.

9. Briefly discuss the function of glycolysis in bioenergetics. What role does NAD play in glycolysis?

10. Discuss the operation of the Krebs cycle and the electron transport chain in the aerobic production of ATP. What is the function of NAD and FAD in these pathways?

Chapter 3


Study Questions

11. What is the efficiency of the aerobic degradation of glucose?

12. What is the role of oxygen in aerobic metabolism?

13. What are the rate-limiting enzymes for the following metabolic pathways: ATP-PC system, glycolysis, Krebs cycle, and electron transport chain?

14. Briefly discuss the interaction of anaerobic versus aerobic ATP production during exercise.

15. Discuss the chemiosmotic theory of ATP production.

Chapter 3


Study Questions

16. List and define the six classes of enzymes identified by the International Union of Biochemistry.

17. Briefly discuss the impact of changes in both temperature and pH on enzyme function.

18. Discuss the relationship between lactic acid and lactate.

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