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Transit and Metabolic Maps:
Complex and Functional
Glycolysis Coupled
with Cellular
Respiration Maximizes
Energy Generation
Carbon Oxidation is Coupled with
Energy Rich Reduction
Which molecule is more energy rich on a per carbon basis?
Free-Energy Universal-Currency: ATP
ATP hydrolysis is exergonic
ATP + H2O ADP + Pi
∆G°ʹ = - 30 kJ/mol
ATP hydrolysis drives
metabolism in heterotrophs
Light energy is trapped as ATP
in phototrophs
Why is ATP an excellent energy
currency?
ATP: High Phosphoryl-Transfer Potential
ATP and hydrolysis products differences:
• Electrostatic repulsion
• Resonance stabilization
• Hydration stabilization
How can an energetically unfavorable
reaction be made spontaneous?
Substrate-Level ATP Phosphoryation
Requires High Phosphoryl-Transfer Potential
Standard Free Energy of Hydrolysis
Duration of Alternative Energy Sources
Anaerobic Systems
ATP: tennis serve
Creatine phosphate: sprint
Glycolysis: 200 m dash
Aerobic Systems
Oxidative phosphorylation:
race > 500 m
ATP: A Multifunctional
Metabolite
High turnover (ca.
90 lbs/24 hrs)
Additional Activated Carriers
Electron carriers in
oxidation-reduction reactions
Nicotinamide Adenine
Dinucleotide (NAD+)
NADH functions in catabolism
NADPH functions in anabolism
Nicotinamide Adenine
Dinucleotide
Phosphate (NADP+)
Additional Activated Carriers
Electron carriers in
oxidation-reduction reactions
FADH functions in both
catabolism and anabolism
Flavin adenine
dinucleotide (FAD)
Substrate Specificity for Dinucleotide
Oxidation-Reduction Reactions
Fatty Acid Biosynthesis via Keto
Reduction to a Methylene Unit
What is the reducing agent for this
reaction?
Coenzyme A: an Activated Carrier of
Two Carbon Fragments
Coenzyme A structure
Acetyl CoA + H2O ↔ Acetate + CoA + H+
∆G°ʹ = -31 kJ/mol
Activated Carries Utilized in Metabolism
Coenzymes Derived from Vitamins
What coenzymes are derived from these vitamins?
Metabolic Regulation
• Substrate accessibility (compartmentalization)
• Enzyme amount (transcriptional and translation control)
• Catalytic activity
(allosteric control,
covalent modifications,
hormone signaling, and
cell energy status)
Energy charge = [ATP] + ½[ADP]/([ATP] + [ADP] + [AMP])
Energy Utilization Linked with Building
and Degrading Metabolites
What macromolecules are stored and/or metabolized by
humans for energy?
Metabolic Fuel Generation by Digestion
Match the enzyme with the
reaction:
- Protease
- Amylase
- Lipase
Lipid Transport via Lipoproteins (aka
Chylomicrons) to Adipocytes
Lipoproteins - esterified cholesterol, proteins and
triacylglycerols combined
Adipose cells
Human Sugar Storage in Liver and Muscle
Tissue
Glycogen molecule with
sugar units
A Liver Cell
Fat
globule
Glycogen granules
Mitochondria
What advantages are there in having glycogen be a
branched polymer?
Glycogen Degradation by Glycogen
Phosphorylase (Phosphorolysiss)
Trapped in the cell
Protein Degradation by Ubiquitin Tagging
and Proteasome Digestion
Protease active sites
Cutaway view showing inner chamber
Proteasome Protein
Degradation
Protein turnover important in:
Cell signaling
Maintaining high protein
quality
Test Your Knowledge…
Does this
phosphoarginine
metabolite rich in the
muscles of certain
invertebrates have
a high
phosphoryl-transfer
potential?
What function might
this metabolite have?
∆G of ATP Hydrolysis with Varying [Mg2+]
How does
decreasing [Mg+2]
affect ∆G of ATP
hydrolysis?
Can this trend be
justified?
Problems: 26, 27 and 41