Bioenergetics

Objectives

• Describe the basic concept of bioenergetics• Describe three major energy substrates and energy

systems• Understand the differences of each energy system• Understand chemical reactions and metabolisms of

each energy system• Understand the interaction among the three energy

systems with respect to intensity and duration differences

Bioenergetics

• For any physical activity, energy must be made and used by the body to accomplish the task (work).

• The study of energy flow in living organisms • How is that energy generated and ultimately

utilized?

Energy Systems• ATP-PCr System

• Specifics• Rate limiting Enzyme• Role during Exercise

• Glycolytic System• Specifics• Rate limiting Enzyme• Role during Exercise

• Oxidative System• Specifics• TCA Cycle• Rate limiting Enzyme• Electron Transport Chain• Role during Exercise

• Lipid Metabolism• Beta Oxidation

• Interaction of Energy Systems

ATP (adenosine triphosphate)ATP = body’s “energy source”

Breaking phosphate bonds through chemical reactions (ATP hydrolysis) releases energy

Energy used for muscle contraction and movement

How does our body make ATP??

Energy

Anaerobic vs. Aerobic

ATP produced through anaerobic and aerobic energy systems

Anaerobic Aerobic

Also called.. Non-oxidative, Glycolytic Oxidative

Type of exercise High-intensity Low-Moderate Intensity

Duration Short duration (<2 min) Longer duration (>2 min)

Oxygen Does Not Require Oxygen Requires Oxygen

Energy Systems ATP-PC; Anaerobic Glycolysis Oxidative Phosphorylation

Energy Production High RateLow Capacity

Low RateHigh Capacity

ATP-PC System

Creatine Kinase

Phosphocreatine

Adenosine Diphosphate

Creatine

Control of ATP-PC System

Activate Inhibit

Creatine Kinase(Rate limiting enzyme)

Exercise and the ATP-PC System

Power

Exercise Example Shot Put

Fuel Storage Site Cytosol

ATP Reformation Rate Very Rapid

Storage Form ATP, PC

Activity Duration 0-3 sec

Glycolytic System

• Glycogen (in liver/muscle) or Glucose (in blood) act as initial substrate

• Energy Investment Phase (use 1 or 2 ATP)• Energy Generation Phase (make 4 ATP)

• End product is Pyruvic acid (pyruvate) which is converted to Lactic Acid (lactate)

2 Phases of Glycolysis

Energy Investment phase

• Requires 2 ATP

Energy Generation phase

• Produces 4 ATP, 2 NADH, 2 pyruvate or 2 lactate

Energy Investment PhaseGlucose

ATPADP

Hexokinase

ATPADP

Phosphofructokinase

Glucose-6-Phosphate

1

Fructose-6-Phosphate2

Fructose-1,6-Diphosphate

3

Energy Investment Phase cont’

Fructose-1,6-Diphosphate

2(Glyceraldehye-3-Phosphate)

Dihydroxyacetone Phosphate

4

5

To Energy Generation Phase

Energy Investment Phase

Energy Generation Phase

NAD+

NADH+H+

ADPATP

2(Glyceraldehye-3-Phosphate)

H2O

2(1,3 Diphosphoglycerate)6

2(3-Phosphoglycerate)

7

2(2-Phosphoglycerate)8

2(Phosphoenolpyruvate)

9

Energy Generation Phase Cont’

2(Phosphoenolpyruvate)

2(Lactic Acid)

11

2(Pyruvic Acid)

10

NADH+H+

NAD+Lactate

Dehydrogenase

ADPATP

Pyruvate Kinase

Energy Generation Phase (2 ATP)

Figure 3.15

Glycolysis

Net Equation for Glycolysis

Control of Glycolytic System

Activate Inhibit

Phosphofructokinase (PFK)(Rate limiting enzyme)

Glycogen vs. GlucoseGlycogen

ATPADPPhosphofructokinase

Glucose-1-Phosphate

Fructose-6-Phosphate

Fructose-1,6-Diphosphate

Glucose-6-Phosphate

No ATP cost!

Glucose

ATP ADP

Exercise and Glycolytic System

Speed

Exercise Example 100-400m run, Basketball

Fuel Storage Site Cytosol

ATP Reformation Rate Rapid

Storage Form Muscle Glycogen

Activity Duration 4-50 sec

Anaerobic Glycolysis vs. Oxidative Phosphorylation

• In the absence of oxygen, pyruvate is converted to lactate

• In the presence of oxygen, pyruvate is shuttled into the mitochondria and begin the Citric Acid Cycle

• TCA Cycle/Krebs Cycle

Mitochondria Structure

TCA Cycle Facts

• Also known as the Krebs Cycle

• Pyruvate from Glycolysis is shuttled into the mitochondria to start the reaction.

• Cycle is made up of 8 distinct reactions.

• Two cycles are completed per G-6-P molecule broken down in Glycolysis.

Pyruvate Conversion

Cytosol

MitochondriaPyruvate

Dehydrogenase

Isocitrate

-ketoglutarate

Succinyl-CoA

Succinate

Fumarate

Malate

Citrate

CoA

NAD+

NAD+

GDPGTP

FADH2

FAD

NADH+H+

NAD+

Acetyl-CoA

Oxaloacetate

H2O

*Rate limitingNADH+H+

NADH+H+

(ATP)

Control of TCA Cycle

Isocitrate Dehydrogenase

(Rate limiting enzyme)

NADHATP

Inhibit

ADP, Pi

NAD+, Ca++

Activate

Electron Transport Chain (ETC) Basics

• Dictated by the Chemiosmotic Theory.(movement of ions across a selectively permeable membrane, down their electrochemical gradient)

• Physically Attached to Cristae of Mitochondria.

• Composed of Complex I-IV, CoQ, Cytochromes, and F-complex (ATP Synthase).

• Multiple ETCs in each mitochondria.

Chemiosmotic Theory

• Transfer of electrons (e-) along protein complexes (enzymes and cytochromes) and pumps protons (H+).

• Pumped protons create an energy gradient.

• Energy gradient is used to re-synthesize ATP from ADP+Pi.

e- flow

1 3 24

Intermembrane Space

MatrixNADH NAD+

2H+

2H+

1H+

FADH2 FADe- flow

2H+

1H+

Outer MembraneInner membrane

Matrix Intermembrane Space

Proton Gradient

2 H+1 H+

FADH2

2 H+

2 H+1H+

NADH

NADH = 5 H+

FADH2 = 3 H+

2 H+

ADP + Pi

ATP

F-Complex

NADH = 2.5 ATP

FADH2 = 1.5 ATP

Phosphorylation

Oxygen Utilization Site

e- flow

½ O2

H2O

Intermembrane Space

Matrix

24

Electron acceptor

2H+ +2e- Oxidation

Electron Transport Chain

Chemiosmotic Hypothesis Pumping of H+ results in H+ gradient across membrane

Movement of H+ ions through channel activates the enzyme ATP synthase

http://www.youtube.com/watch?v=3y1dO4nNaKY

Amount of ATP per NADH/FADH

2 H+ 2 H+ 1 H+

2 H+ needed to produce and transport 1 ATP

NADH: 5 H+/2 H+ per ATP = 2.5 ATPFADH: 3 H+/2 H+ per ATP = 1.5 ATP

Tally of ATP ProductionProcess Product Total ATP

Pyruvate Acetyl-CoA

2 NADH

TCA Cycle

2 GTP

6 NADH

2 FADH2

2

5Glycolysis

2 ATP

2 NADH

5

2

15

3

TOTAL = 32 / Glucose

(2 ATP)

(2.5 ATP per 1 NADH) (1.5 ATP per 1 FADH2)

Exercise and Oxidative System

Endurance

Exercise Example >1500m run

Fuel Storage Site Cytosol, blood, liver, fat

ATP Reformation Rate Very Slow

Storage Form Glycogen, lipids, amino acids

Activity Duration >2 min

Maximal Duration of Energy System

30 sec

1 min

3 min

5 min

2-3 hr

% C

ontr

ibuti

on

ATP-PC

Glycolysis

Oxidative

10 sec

Specific Rate-Limiting Enzymes

Lipid MetabolismThree types of Lipids:

1) Fatty Acids2) Triglycerides (storage form)3) Phospholipids

• Requires more Oxygen and generates more ATP than Carbohydrate metabolism

• Lean individual can store ~75,000 kcal of energy as Triglycerides.

• Lean individual can store ~2,500 kcal of energy as Glycogen.

Triglyceride Lipolysis

• Catalyzed by the enzyme Hormone-Sensitive Lipase.

• FFA released into blood.• Transported to muscle cells based on

concentration gradient.

Fatty Acid

Fatty Acid

Fatty Acid Glycerol

Fatty Acids• Carboxylic acid with long aliphatic tail (chain) • Mostly natural FA has even number of carbon atoms, from 4 to 28

Beta Oxidation of Fatty Acids

• Occurs in the Matrix of the Mitochondria.• 4 distinct reactions.• Final product is a Fatty Acid (shortened by two

carbons) and Acetyl-CoA.• Acetyl-CoA enters the TCA cycle, and Fatty

Acid undergoes another round of Beta-Oxidation.

Series of steps in which two-carbon acyl units are chopped off of the carbon chain of the FFA

Acetyl-CoA

Saturated Fatty Acid

Product 3

Product 2

Product 1

FAD

FADH2

NAD+

NADH

Acyl-CoA Dehydrogenase

Enoyl-CoA Hydratase

Hydroxyacyl-CoA Dehydrogenase

Thiolase

Beta Oxidation of Fatty Acids

ATP Tally for Palmitic Acid (16 C)

Start Beta-Oxidation

Product ATP Value

- 2 ATP - 2

7 Cycles of Beta-Oxidation

7 NADH7 FADH2

17.510.5

8 TCA Cycles24 NADH

8 FADH2

8 GTP

60128

Grand Total = 106 ATP

For Activation

(2.5 ATP per 1 NADH) (1.5 ATP per 1 FADH2)

Beta Oxidation during Exercise

Used to produce ATP:1. At rest in exercise trained individuals.2. When exercise intensity is low (< 40% max

effort)3. When Glycogen is not abundant (end of long

duration exercise)

Its response is mediated by the “Crossover Effect”

Crossover Effect

% of max

% U

tiliz

ation

CHO

Fat35-40% of VO2 max