Download Lecture 5 & 6 Metabolism S11 Chpt. 6 for HO

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Metabolism: Fueling Cell
Growth
Principles of Metabolism
Cells (including your own) must:
• Synthesize new components
(anabolism/biosynthesis)
• Harvest energy and convert it to
a usable form (catabolism)
Principles of Metabolism
The role of ATP
energy currency
Adenosine triphosphate
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Principles of Metabolism
The role of ATP
energy currency
Principles of Metabolism
Harvesting energy - Oxidation of the chemical energy source
releases energy (ex. glucose → CO2)
•Oxidation/reduction reactions (redox reactions)
electron donor
electron acceptor
OIL – Oxidation is loss of electrons
RIG – Reduction is gain of electrons
Principles of Metabolism
The role of electron carriers
“reducing power”
In redox reactions, protons often follow electrons
e- + H+ = H
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Principles of Metabolism
The role of electron carriers
12 pairs of electrons (snatched by electron carriers)
Glucose →→→→→→→6 CO2
•Passed to the electron transport
chain ((used to create the proton
p
motive force); ultimately passed to
a terminal electron acceptor (such
as O2, making H2O)
•Used in biosynthesis (to reduce
compounds)
Principles of Metabolism
Synthesizing ATP
•Substrate-level phosphorylation
Principles of Metabolism
Synthesizing ATP
•Substrate-level phosphorylation
•Oxidative phosphorylation - the energy of proton motive force is
harvested; chemical energy is used to create the proton motive force
(involves an electron transport chain)
ATP
synthase
ADP + Pi → ATP
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Principles of Metabolism
Synthesizing ATP
•Substrate-level phosphorylation
•Oxidative phosphorylation - the energy of proton motive force is
harvested; chemical energy is used to create the proton motive force
(involves an electron transport chain)
•Photophosphorylation
Photophosphorylation - the energy of proton motive force is
harvested; radiant energy is used to create the proton motive force
(involves an electron transport chain)
Scheme of Metabolism
energy source terminal electron acceptor
Glucose (C6H12O6) + O2
Energy
ATP (substrate-level phosphorylation)
Energy
NADPH
NADH/FADH2 → electron transport chain
↓
proton motive force
↓
ATP (oxidative phosphorylation)
Energy
Energy
Carbon dioxide
(CO2) +
H2 O
Scheme of Metabolism
energy source terminal electron acceptor
Glucose (C6H12O6) + O2 Energy (heat) Carbon dioxide
(CO2) +
H2 O
Energy
Energy
Energy
Energy
Carbon dioxide
(CO2) +
H2 O
Figure 6.23
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Scheme of Metabolism
Central Metabolic Pathways
Central Metabolic Pathways
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Central Metabolic Pathways
Glycolysis (aka Embden-Meyerhoff
pathway, glycolytic pathway)
glucose→ 2 pyruvate
•2 ATP (net gain)
•2 spent; 4 made
•2 NADH
•six different p
precursor metabolites
Central Metabolic Pathways
Glycolysis (aka Embden-Meyerhoff
pathway, glycolytic pathway)
glucose→ 2 pyruvate
•2 ATP (net gain)
•2 spent; 4 made
•2 NADH
•six different p
precursor metabolites
Central Metabolic Pathways
Glycolysis (aka Embden-Meyerhoff
pathway, glycolytic pathway)
glucose→ 2 pyruvate
•2 ATP (net gain)
•2 spent; 4 made
•2 NADH
•six different p
precursor metabolites
Pentose phosphate pathway (not pictured)
glucose→ intermediate of glycolysis
•NADPH (amount varies)
•two different precursor metabolites
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Central Metabolic Pathways
Central Metabolic Pathways
Transition step
pyruvate (3 C) → acetyl CoA (2 C) + CO2
(twice per glucose)
•NADH
•One precursor metabolite
Central Metabolic Pathways
TCA cycle (aka Kreb’s cycle, citric acid cycle)
acetyl CoA (2 C) → 2 CO2
(twice per glucose)
•ATP
•3 NADH
•FADH2
•two
t
different
diff
t precursor
metabolites
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Central Metabolic Pathways
Central Metabolic Pathways
Central Metabolic Pathways
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Central Metabolic Pathways
Review
Which central metabolic pathway generates the
most reducing power?
Review
How would a bacterium use protein as an energy source?
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Central Metabolic Pathways
Scheme of Metabolism
energy source terminal electron acceptor
Glucose + O2 (C6H12O6)
Energy
ATP (substrate level phosphorylation)
Energy
Energy
Energy
Carbon dioxide
NADH/FADH2 → electron transport chain
↓
proton motive force
↓
ATP (oxidative phosphorylation)
(CO2) +H2O
Glucose has been
oxidized, but where do
the electrons go???
Central Metabolic Pathways
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Electron Transport Chain
of mitochondria
Part of figure 3.55
Electron Transport Chain
of mitochondria
Terminal electron acceptor
FADH2 → FAD
Electron Transport Chain
of mitochondria
Creates the proton motive force
FADH2 → FAD
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Electron Transport Chain
The Mechanics
2e-
2H+
Electron Transport Chain
Mitochondrial matrix
(inside)
NADH + H+
Intermembrane space
(outside)
Hydrogen carrier
Electron carrier
Hydrogen carrier
Electron carrier
2H+
Hydrogen carrier
2H+
Electron carrier
Electron Transport Chain
of mitochondria
FADH2 → FAD
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Electron Transport Chain
of E. coli
oxidase test
Aerobic respiration (shown)
Anaerobic respiration
•NO3 as a TEA (different ubiquinol oxidase)
•Quinone used provides humans with vitamin K
FADH2 → FAD
Pathway
Eukaryote
Prokaryote
Glycolysis
Cytoplasm
Cytoplasm
Intermediate step
Cytoplasm
Cytoplasm
TCA cycle
Mitochondrial matrix
Cytoplasm
ETC
Mitochondrial inner
membrane
Plasma
membrane
Overall Maximum Energy Yield
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Overall Maximum Energy Yield
Overall maximum energy yield of aerobic
respiration (ignoring the pentose
phosphate pathway):
Complete oxidation of glucose
4 ATP
10 NADH
2 FADH2
Electron
El
t
transport
t
t
chain (oxidative
phosphorylation)
•3 ATP/NADH
•2 ATP/FADH2
Overall Maximum Energy Yield
Overall maximum energy yield of aerobic
respiration (ignoring the pentose
phosphate pathway):
Complete oxidation of glucose
4 ATP
10 NADH
2 FADH2
Electron
El
t
transport
t
t
chain (oxidative
phosphorylation)
•3 ATP/NADH
•2 ATP/FADH2
38 ATP (maximum theoretical)
Overall Maximum Energy Yield
Overall maximum energy yield of aerobic
respiration (ignoring the pentose
phosphate pathway):
Complete oxidation of glucose
4 ATP
10 NADH
2 FADH2
Electron
El
t
transport
t
t
chain (oxidative
phosphorylation)
•3 ATP/NADH
•2 ATP/FADH2
4 + 34= 38 ATP (maximum theoretical)
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Fermentation
•Used when respiration is not
an option
•
•
Lack of TEA
No electron transport chain
•Oxidation of glucose stops at
pyruvate
Fermentation
•Used when respiration is not
an option
•
•
Lack of TEA
No electron transport chain
•Oxidation of glucose stops at
pyruvate
•Passes electrons from NADH
to pyruvate or a derivative
NAD
NADH
The logic:
•Oxidizes NADH, generating NAD for use in further rounds of glucose breakdown
•Stops short of the transition step and the TCA cycle, which together generate 5X
more reducing power
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Fermentation
Fermentation
Review
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Review
Energy source versus terminal electron acceptor
Glucose + 6 O2 → 6 CO2 + 12 H2O
Enzymes
• A specific, unique, enzyme
catalyzes each biochemical
reaction
• Enzyme activity can be
controlled by a cell
• Enzymes can be exploited
medically, industrially
• Enzyme names usually
reflect the function and end
in -ase
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Enzymes
Enzymes
What are allosteric enzymes and why are they important?
Enzymes
Enzyme inhibition
Non-competitive inhibition - Inhibitor/substrate act at different sites
•Regulation (allosteric)
•Enzyme poisons (example: mercury)
Competitive inhibition - Inhibitor/substrate act at same site
Ex.: → PABA → → folic acid → coenzyme
Sulfa
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Enzymes
Environmental factors influence enzyme activity
temperature, pH, salinity
Enzymes
Cofactors act in conjunction with certain enzymes
Coenzymes are organic cofactors
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