Download Bioenergetics Objectives Objectives

Chapter 3
Bioenergetics
Objectives
• Discuss the function of cell membrane,
nucleus, & mitochondria
• Define: endergonic, exergonic, coupled
reactions & bioenergetics
• Describe how enzymes work
• Discuss nutrients used for energy
• Identify high-energy phosphates
Objectives
• Discuss anaerobic & aerobic production
of ATP
• Describe how metabolic pathways are
regulated
• Discuss the interaction of anaerobic &
aerobic ATP production during exercise
• Identify the rate limiting enzymes
1
Metabolism
• Total of all chemical reactions that occur in
the body
• Bioenergetics
Cell Structure
• Cell membrane
• Nucleus
• Cytoplasm
Structure of a Typical Cell
2
Cellular Chemical Reactions
• Endergonic reactions
• Exergonic reactions
• Coupled reactions
The Breakdown of Glucose:
An Exergonic Reaction
Coupled Reactions
3
Enzymes
• Catalysts that regulate the speed of
reactions
• Factors that regulate enzyme activity
• Interact with specific substrates
Enzyme-Substrate Interaction
Fuels for Exercise
• CHO
• Fats
• PRO
4
High-Energy Phosphates
• Adenosine triphosphate (ATP)
• Formation
• Breakdown
Structure of ATP
Model of ATP as the Universal
Energy Donor
5
Bioenergetics
• Formation of ATP
• Anaerobic pathways
• Aerobic pathways
Anaerobic ATP Production
• ATP-PC system
PC + ADP
Creatine kinase
ATP + C
• Glycolysis
– Energy investment phase
– Energy generation phase
The Two Phases of Glycolysis
6
Glycolysis:
Energy Investment Phase
Glycolysis:
Energy Generation Phase
Oxidation-Reduction Reactions
• Oxidation
• Reduction
• Nicotinomide adenine dinucleotide (NAD)
NAD + 2H+ → NADH + H+
• Flavin adenine dinucleotide (FAD)
FAD + 2H+ → FADH2
7
Production of Lactic Acid
• Normally, O2 is available in the
mitochondria to accept H+ (and e-) from
NADH produced in glycolysis
• H+ & e- from NADH are accepted by
pyruvic acid to form lactic acid
Conversion of Pyruvic Acid to
Lactic Acid
Aerobic ATP Production
• Krebs cycle (citric acid cycle)
• Electron transport chain (ETC)
8
The Three Stages of Oxidative
Phosphorylation
The Krebs Cycle
Relationship b/n the Metabolism of
Proteins, Fats & Carbohydrates
9
Formation of ATP in the ETC
The Chemiosmotic Hypothesis of
ATP Formation
• ETC chain results in pumping of H+ ions
across inner mitochondrial membrane
• Energy released to form ATP as H+ diffuse
back across the mb
The Chemiosmotic Hypothesis of
ATP Formation
10
Aerobic ATP Tally
Metabolic Process
High-Energy
Products
ATP from Oxidative ATP Subtotal
Phosphorylation
Glycolysis
2 ATP
2 NADH
—
6
2 (if anaerobic)
8 (if aerobic)
Pyruvic acid to acetyl-CoA 2 NADH
6
14
Krebs cycle
—
18
4
16
34
38
2 GTP
6 NADH
2 FADH
Grand Total
38
Efficiency of Oxidative
Phosphorylation
• Aerobic metabolism of 1 molecule of glu
• Aerobic metabolism of 1 molecule of glycogen
• Overall efficiency of aerobic respiration is 40%
Control of Bioenergetics
• Rate-limiting enzymes
• Levels of ATP and ADP+Pi
• Calcium may stimulate aerobic ATP
production
11
Action of Rate-Limiting Enzymes
Control of Metabolic Pathways
Pathway
Rate-Limiting
Enzyme
Stimulators
Inhibitors
ATP-PC system
Creatine kinase
ADP
ATP
Glycolysis
Phosphofructokinase AMP, ADP, Pi, ↑pH ATP, CP, citrate, ↓pH
Krebs cycle
Isocitrate
dehydrogenase
ADP, Ca++, NAD
ATP, NADH
ATP
Electron transport Cytochrome Oxidase ADP, Pi
chain
Control of Bioenergetics
Glycogen
ATP-PC System
PC + ADP
C + ATP
Glucose
1
Glucose 6-phosphate
Glycerol
Triglycerides
2
Phosphoglyceraldehyde
Glycolysis
Pyruvic Acid
Lactic Acid
β-ox
Acetyl CoA
Fatty acids
Ketone
bodies
C4
Kreb’s
Cycle
3
Amino Acids
C6
C5
Proteins
Urea
NADH
FADH
ETS
4
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Interaction b/n Aerobic &
Anaerobic ATP Production
• Energy to perform exercise comes from an
interaction b/n aerobic & anaerobic pathways
• Effect of duration & intensity
– Short-term, high-intensity activities
– Long-term, low to moderate-intensity exercise
β-Oxidation A Closer Look - 3.4
13
β-Oxidation
β-Oxidation
• Long chain FA
• Activated FA Î acetyl-CoA
4 Steps to β-Oxidation
• Step 1: FA Î Activated FA
• Step 2: Oxidization of activated FA Î fatty acetylCoA
• Step 3: fatty acetyl-CoA Î β-hydroxyl acetyl-CoA
• Step 4: β-hydroxyl acetyl-CoA Î Activated FA +
Acetyl CoA
14
β-Oxidation
• Example: Palmate (Palmitic acid)
synthesis
C16H32O2
C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-C
1
2 3
4
5 6
7
β-Oxidation
•
•
•
•
•
•
•
Total ATP Tally = Palmitic Acid
1 ATP investment (activation of FA)
β-oxidization = 5 ATP (1 NADH + H+; 1FADH2)
1 Acetyl-CoA molecule enters Krebs Cycle
1ATP
3 NADH + H+ ………ETC = 9 ATP
1 FADH2…………….ETC = 2 ATP
β-Oxidation
• TOTAL ATP generation = Palmitic Acid
15
Play it again Sam…
• How about Stearic Acid (C18H36O2)
• β-Oxidization Î (18/2)-1 = 8 turns
– ATP investment = 1 ATP
– 1 NADH + H+; 1FADH2
•
•
•
•
x 8 turns = 40 ATP -1 = 39 ATP
9 Acetyl-CoA molecules enter into Krebs Cycle
9 ATP
3 NADH + H+ x 9 turns = 81 ATP in ETC
1 FADH2 x 9 turns = 18 ATP in ETC
Total ATP Production = 147 ATP
Bottom Line…
But is it Efficient?
16
Hey Fatty, remember me?
• Recall this term
What about the glycerol backbone?
• Converted to 3-phosphoglyceraldehyde
(glycolysis)
17