Transcript
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
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