Biochemistry: A Short Course

1
CHAPTER 15 Basic Concepts and Design
in Metabolism
Glycolysis Coupled with Cellular Respiration
Maximizes Energy Generation
Why are these coupled pathways so important?
2
Transit and Metabolic Maps Complex and Functional
3
Carbon Oxidation is Coupled with Energy Rich
Reduction
Which molecule is more energy rich on a per
carbon basis?
4
Free-Energy Universal-Currency ATP
ATP hydrolysis is exergonic ATP H2O ADP Pi
?G' - 30 kJ/mol ATP hydrolysis drives
metabolism in heterotrophs Light energy is
trapped as ATP in phototrophs
Why is ATP an excellent energy currency?
5
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?
6
Substrate-Level ATP Phosphoryation Requires High
Phosphoryl-Transfer Potential
7
ATP Phosphoryl-Transfer Hub
8
Duration of Alternative Energy Sources
Anaerobic Systems
Aerobic Systems ATP tennis serve
Oxidative phosphorylation Creatine
phosphate sprint race gt 500
m Glycolysis 200 m dash
9
ATP A Multifunctional Metabolite
High turnover (ca. 90 lbs/24 hrs)
10
Additional Activated Carriers
Nicotinamide Adenine Dinucleotide (NAD)
Electron carriers in oxidation-reduction
reactions NADH functions in catabolism NADPH
functions in anabolism
Nicotinamide Adenine Dinucleotide Phosphate
(NADP)
11
Additional Activated Carriers
Electron carriers in oxidation-reduction
reactions FADH functions in both catabolism and
anabolism
Flavin adenine dinucleotide (FAD)
12
Substrate Specificity for Dinucleotide
Oxidation-Reduction Reactions
13
Fatty Acid Biosynthesis via Keto Reduction to a
Methylene Unit
What is the reducing agent for this reaction?
14
Coenzyme A an Activated Carrier of Two Carbon
Fragments
Coenzyme A structure
Acetyl CoA H2O ? Acetate CoA H
?G' -31 kJ/mol
Is acetyl coenzyme A a dinucleotide?
15
Activated Carries Utilized in Metabolism
16
Coenzymes Derived from Vitamins
What coenzymes are derived from these vitamins?
17
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 ½ADP/(ATP ADP
AMP)
18
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?
19
?G of ATP Hydrolysis with Varying Mg2
How does decreasing Mg2 affect ?G of ATP
hydrolysis? Can this trend be justified?
20
Chapter 15 Problems 1-8, 10-16 and
18-20 Workbook Problems page 84 all questions
and Page 85-87 questions 1-7 Please note
question 2 page 85 has a typo the two ?Gs
should read ?G and ?G?'