Download Bioenergetics

Anaerobic ATP Production
1. ATP-PC system
Chapter 3,
– Immediate source of ATP
Part 2
PC + ADP
Creatine kinase
ATP + C
Bioenergetics
Anaerobic ATP Production
Energy Transfer Systems and Exercise
100%
% Capacity of Energy System
2. Anaerobic Glycolysis
Anaerobic
Glycolysis
Aerobic
Energy
System
– Produces ATP through a biochemical process
– Food source is glycogen or glucose
Glycogenolysis-breakdown of glycogen stored in
muscle (glycogen is also stored in liver)
Glycolysis-breakdown of glucose
ATP - CP
10 sec
30 sec
2 min
5 min +
Anaerobic ATP Production
Glycolysis
– Energy investment phase
Requires 2 ATP
The Two
Phases of
Glycolysis
– Energy generation phase
Produces ATP, NADH (carrier molecule), and
pyruvate or lactate
Fig 3.10
1
Glycolysis
Glucose – C6H12O6
Pyruvic Acid - C3H4O3
Glycolysis
– C6H12O6 ⎯→ 2 C3H4O3 + 2 H+ + energy (2
ATP)
W/ O2
Production of Lactic Acid
Normally, O2 is available in the
mitochondria to accept H+ (and electrons)
from NADH produced in glycolysis
– In anaerobic pathways, O2 is not available
H+ and electrons from NADH are accepted
by pyruvic acid to form lactic acid
– NAD + 2 H+ → NADH + H+ (Krebs cycle)
Anaerobic Glycolysis
Conversion of Pyruvic Acid
to Lactic Acid
Lactic Acid – C3H6O3
– C6H12O6 ⎯→ 2 C3H6O3 + energy (2 ATP)
W/O O2
Fig 3.12
Anaerobic Glycolysis
Characteristics
– Begins about 20 sec into high intensity
exercise and continues for about 3 minutes
– Uses only glucose or glycogen
– Enzymes located in the cytoplasm
– 12 biochemical steps producing 2 to 3 ATP
– Intensity less than 100% (70-90% max)
Anaerobic Glycolysis
Characteristics (cont)
– Does not require oxygen
– Limited at about 3 min by the buildup of lactic
acid which decreases the pH
– Acidic environment halts enzyme activity
Phosphofructokinase (PFK)
– Glucose – 2 ATP
– Glycogen – 3 ATP
2
Glycolysis
Energy Investment Phase
The Two
Phases of
Glycolysis
Fig 3.11
Fig 3.10
Glycolysis
Energy Generation Phase
Energy Transfer Systems and Exercise
100%
% Capacity of Energy System
Anaerobic
Glycolysis
Aerobic
Energy
System
ATP - CP
10 sec
30 sec
2 min
5 min +
Fig 3.11
Aerobic ATP Production
3. Krebs cycle (citric acid cycle, TCA
cycle)
– Completes oxidation of H+
– Removed from CHO, fats, Proteins
– NAD, FAD – H+ carriers
– H+ contains potential energy from food
molecules
Aerobic ATP Production
H+ transported to electron transport chain
– Combines ADP + P → ATP
Oxygen availability
– Final hydrogen acceptor
– Forms H2O
3 steps
– Breakdown of foodstuffs
– Oxidative phosphorylation
– Electron transport chain
3
The Krebs Cycle
The Three
Stages of
Oxidative
Phosphorylation
Fig 3.13
Relationship Between the
Metabolism of Proteins, Fats, and
Carbohydrates
Fig 3.15
Aerobic Glycolysis
Electron Transport System (chain)
H+ + e- + O2 → H2O
ADP + Pi → ATP
Fig 3.14
Electron Transport Chain
Fig 3.17
Beta Oxidation
Breakdown of lipids
1 ATP required for fats to be activated for
– ß oxidation process
Fats enter at Krebs cycle and pass to ETC
Fats produce much higher amounts of
ATP per mol. than glycogen
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Beta Oxidation
2 C fat compound
– Stearic acid is an 18 C fat
yields 147 ATP
– Palmitic acid is a 16 C fat
130 ATP
Fats require 15% more oxygen per ATP
produced than CHO require
Fats cannot be metabolized anaerobically
Aerobic
Characteristics
– Requires presence of oxygen (aerobic)
– Can use glucose, glycogen, fatty acids, and/or
amino acids for fuel
– Provides 85% of the energy required by body
15% glycolysis
– Produces ATP during rest and low level
exercise
Aerobic
Characteristics (cont)
– Oxidative phosphorylation occurs in
mitochondria
– Makes relatively large amounts of ATP
– Glycogen = 33 ATP
– Glucose = 32 ATP
Aerobic
Aerobic
Glycogenolysis
Glycogen
→ 3 ATP + 2 Pyruvic Acid
→ 3 ATP + 2 C3H4O3
– (C6H12O6)n
Glycolysis
Glucose
– C6H12O6
→ 2 ATP + 2 Pyruvic Acid
→
2 ATP + 2 C3H4O3
Mitochondria
2 Pyruvates → 2 Acetyl CoA (CO2)
Krebs cycle (TCA cycle)
2 Acetyl CoA → 6 CO2 + 6 H2O + 33 (or
32) ATP
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Efficiency of Oxidative
Phosphorylation
Mitochondria
Outer membrane permeable to most ions
Inner membrane impermeable to most
ions unless they have a specific carrier
Bulges of the inner membrane – cristae
Density of cristae higher in tissues with
high rate of oxidation
Aerobic metabolism of one molecule of
glucose
– Yields 32 ATP
Aerobic metabolism of one molecule of
glycogen
– Yields 33 ATP
Overall efficiency of aerobic respiration is
34%
– heart
– 66% of energy released as heat
Aerobic system
Control of Bioenergetics
Summary Equation
C6H12O6 + 6 O2 + 32 ADP + 32 Pi →
Rate-limiting enzymes
– An enzyme that regulates the rate of a
metabolic pathway
– 6 CO2 + 6 H2O + 32 ATP
Levels of ATP and ADP+Pi
(C6H12O6)n + 6 O2 + 33 ADP + 33 Pi →
– 6 CO2 + 6 H2O + 33 ATP
Control of Metabolic Pathways
Pathway
ATP/PC
Glycolysis
Rate-limiting
creatine kin
PFK
Krebs
ETC
Isocitr dehy
cyto oxidase
Stim Inh
ADP ATP
AMP ATP
ADP CP
↑ pH Pi ↓
ADP ATP
ADP ATP
– High levels of ATP inhibit ATP production
– Low levels of ATP and high levels of ADP+Pi
stimulate ATP production
Interaction Between Aerobic
and Anaerobic ATP Production
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
Table 3.2
6
Exercise Time and Lactate
Production
E nerg y Transfer S ys tem s an d E xercise
100%
% Capacity of Energy System
A naerobic
G lyc olys is
A ero bic
E nergy
S ystem
ATP - CP
10 sec
3 0 se c
2 m in
5 m in +
Regulation of Metabolism
Low Intensity
– < 40-50% VO2max
Medium Intensity
– 50-70% VO2max
High Intensity
– 70-120% VO2max
Energy Systems during
Exercise
Submaximal
– 2/3 fat
– 1/3 CHO (glucose/glycogen)
– Steady state-oxygen consumption meets
oxygen demand to provide ATP
– Adjustment time needed to reach steady state
– 30 min or more
Energy Systems during
Exercise
Submaximal (cont)
– Major fuel is fat
– ATP-PC and LA contribute during the first 2-3
min of exercise
– BLa is not high so anaerobic glycolysis and
LA are not primary contributor
– BLa of marathoners is only about 20-30 mg%
7
Energy Systems during
Exercise
Submaximal (cont) – forever?
Fatigue factors
low blood glucose (liver glycogen
depletion)
low muscle glycogen-muscular fatigue
dehydration and electrolyte loss (core
temp)
boredom, physical beating
Energy Systems during
Exercise
Maximal exercise
– 1/4 fat
– 3/4 CHO (glucose/glycogen)
Anaerobic sources
Summary
The key determining factor in which
energy system predominates:
– Exercise intensity
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