bioenergetics and introduction to metabolism -3...9/30/2012 1 bioenergetics and introduction to...
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Bioenergetics and Introduction to Metabolism -3
The transfer and utilization of energy in biologic systems
Lippincott chapter 6
O2
CO2
ATP is not a long term storage form of energy
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Approximate glucose uptake and ATP turnover by various tissues
Tissue Approximate O2consumption
mole/ day
Equivalent glucose
mole/ day
ATP turnover mole/day
Brain 3.4 0.57 20.4Heart 1.9 0.32 11.4Kidney 2.9 0.49 17.4Liver 3.6 0.6 21.6Muscle 3.3 0.54 19.8Total 15.1 2.52 90.6
• Based on O2 consumption• Assuming glucose is the fuel used
C6H12O6 + 6O2 6CO2 + 6H2O + 36ATP
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Caloric value and free energy changes for complete oxidation of some fuels
Compound ΔGºkcal/mol
Molecular weight
Caloric value
Glucose 686 180 3.8
Palmitate 2380 256 9.3
Glycine 234 75 3.1
Glucose + O2 → CO2 + H2O 686 kcal/mole
Other nucleotide triphosphates
• GTP, UTP, CTP• Synthesized from ATP
ATP + GDP ADP + GTP– GTP in protein synthesis– UTP in polysaccharide synthesis– CTP in phospholipids synthesis
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UDP- is a carrier of activated sugar
UDP-glucose in glycogen synthesis
• Glycogen synthesis from glucose requires energy– Glucose Glycogen + H2O
• UDP-glucoseis the activated carrier of glucoseUTP + Glucose 1-P UDP-Glc + PPi
UDP-Glc + Glycogen(n) UDP + Glycogen(n+1)
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Acetyl Coenzyme A is a high energy compound
• Coenzyme A is a universal carrier of Acyl groups• Forms thioester bond with carboxyl group
O O װ װ
• RC~S-CoA CH3C~S-CoA
Acyl CoA Acetyl CoA
Acetyl CoA + H2O Acetate + CoA ΔGº = -7.5kcal
Acetylcholine + H2O Acetate + Choline ΔGº = -3 kcal
Adenine
Ribose
2 phosphate
s
Pantothenic acid
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Coenzyme A is a donor of Acyl groups
Acetate + Choline Acetylcholine + H2O ΔGº = +3 kcal
Acetyl CoA + H2O Acetate + CoA ΔGº = -7.5kcal
Acetyl CoA + Choline Acetylcholine + COA
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Oxidation of fuel molecules occurs in two stages
• Oxidation: Loss of electrons• Reduction: Gain of electrons• Aerobic oxidation: Transfer of electrons to
oxygen
- 1st stage: Transfer of e to electron carrier- 2nd stage: Transfer of e to oxygen
Fuel electron carrier Oxygen
A•• A
Carrier carrier••
O•• O
ADP + PiATP
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Electron carriers• Electron carriers are dinucleotides• Nucleotide is formed from
Phosphate- ribose- Nitrogenous base• Two nucleotides connected through
phosphate Dinucleotide • One of the bases is Adenine
• NAD+: Nicotinamide Adenine Dinucleotide• FAD: Flavin Adenine Dinucleotid
Base Ribose
P PRibose Adenine
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Reduction potential
• A- + B A + B-Type of reactionWhat determine the direction of the reaction?
• A+ + B+++ A++ + B++
Type of reactionWhat determine the direction of the reaction?
P P
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Reduction potential and direction of the reaction
A + B- A- + B ΔGº = -veB oxidized formB- reduced form
A
A-
B
B-
V
Redox couple
Reduction potential and direction of the reaction
H+ + X- H2 + X ΔGº = -veX oxidized formX- reduced form
X
X-
H+
V
Redox couple
H2
X- has higher tendency to loose electrons than H2 does
Negative reduction potential
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Reductionpotential: Ability to acceptelectronsOxidized + e- Reduced ΔEº
Succinate α ketoglutarate - 0.67
Acetate Acetaldehyde - 0.60
NAD+ NADH - 0.32
Acetaldehyde Ethanol - 0.20
Pyruvate Lactate - 0.19
Fumarate Succinate + 0.03
Cytochrome+3 Cytochrome+2 + 0.22
oxygen water + 0.82
Calculation of ΔGº from ΔEº• ΔGº = - nF ΔEº
– F = Farady constant = 23.06 kcal/ Volt
• Calculate ΔGº of the following reaction
NADH + 1/2O2 NAD+ + H2O
NADH NAD+ + 2e- ΔEº = +0.32O + 2e- O2- ΔEº = +0.82
ΔGº = - 52.6 kcal/mol
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Degradation and synthesis occur in a stepwise manner
A GNot a single step but a sequence of steps
A B C D E F G
Called metabolic pathwayAnabolic or Catabolic