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REDOX REACTIONS
Reduction
Oxidation
• Electrons gained
• Electrons lost
• H atoms added
• H atoms lost
• from O > C
• From C to O
• Oxygen removed
• Oxygen gained
• Energy Stored
• Energy released
• Anabolic
• Catabolic
• Simple > complex
• Complex > simple
• Endergonic
• Exergonic
• Photosynthesis
• Cellular Respiration
REDOX REACTIONS
Reduction
∆G = ∆H - T∆S
Oxidation
• Nonspontaneous
• Spontaneous
• ∆ G (+)
• ∆ G (-)
• >H , <S, >G
• <H , >S, <G
Photosynthesis vs. Respiration
• Photosynthesis:
6 H2O + 6 CO2 + energy
C6H12O6 + 6 O2
reduction
oxidation
Respiration:
C6H12O6 + 6 O2
6 H2O + 6 CO2 + energy
reduction
oxidation
Figure 9.4 NAD+ as an electron shuttle
LE 9-5a
Free energy, G
H2 + 1/2 O2
Explosive
release of
heat and light
energy
H2O
Uncontrolled reaction
LE 9-5b
+
2H
1 /2
O2
1/2
O2
(from food via NADH)
Free energy, G
2 H+ + 2 e–
Controlled
release of
energy for
synthesis of
ATP
ATP
ATP
ATP
2 e–
2
H+
H2O
Cellular respiration
LE 9-5
H2 + 1/2 O2
+
2H
1 /2
O2
1/2
O2
(from food via NADH)
Explosive
release of
heat and light
energy
Free energy, G
Free energy, G
2 H+ + 2 e–
Controlled
release of
energy for
synthesis of
ATP
ATP
ATP
ATP
2 e–
2
H+
H2O
Uncontrolled reaction
H2O
Cellular respiration
3 Types of phosphorylation: ADPATP
• Photophosphorylation - in Noncyclic Photosynthesis in
ETC between PSII & PSI;
• using the energy of sunlight to create a high-energy electron donor
and a lower-energy electron acceptor.
• Substrate phosphorylation -in glycolysis and Krebs cycle;
• Direct transfer of Pi to ADP by an enzyme- A KINASE
• In both aerobic and anaerobic respiration – no O2 needed
• Oxidative phosphorylation- at ATP synthase; result of
proton gradient; electrons from NADH or FADH2 transferred
to O2
Figure 9.6 An overview of cellular respiration (Layer 1)
Figure 9.7 Substrate-level phosphorylation
Figure 9.6 An overview of cellular respiration (Layer 2)
Figure 9.6 An overview of cellular respiration (Layer 3)
Chemiosmosis
 Glycolysis
• Glycolysis Animation option I (simple)
• Glycolysis Animation option II (intermediate)
• Glycolysis Animation option III (advanced)
LE 9-9a_1
Glucose
ATP
Hexokinase
ADP
Glucose-6-phosphate
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
LE 9-9a_2
Glucose
ATP
Hexokinase
ADP
Glucose-6-phosphate
Phosphoglucoisomerase
Fructose-6-phosphate
ATP
Phosphofructokinase
ADP
Fructose1, 6-bisphosphate
Aldolase
Isomerase
Dihydroxyacetone
phosphate
Glyceraldehyde3-phosphate
Glycolysis
Citric
acid
cycle
ATP
ATP
Oxidation
phosphorylation
ATP
LE 9-9b_1
2 NAD+
Triose phosphate
dehydrogenase
2 NADH
+ 2 H+
1, 3-Bisphosphoglycerate
2 ADP
Phosphoglycerokinase
2 ATP
3-Phosphoglycerate
Phosphoglyceromutase
2-Phosphoglycerate
LE 9-9b_2
2 NAD+
Triose phosphate
dehydrogenase
2 NADH
+ 2 H+
1, 3-Bisphosphoglycerate
2 ADP
Phosphoglycerokinase
2 ATP
3-Phosphoglycerate
Phosphoglyceromutase
2-Phosphoglycerate
2 H2O
Enolase
Phosphoenolpyruvate
2 ADP
Pyruvate kinase
2 ATP
Pyruvate
GLYCOLYSIS
GLUCOSE
C-C-C-C-C-C
AT
P
IN
CYTOSOL
•Prepartory Steps
•Energy Investment
Phase
ATP
PGAL C-C-C
NADOX
NADre
= NAD+
PGAL C-C-C
NAD+
NAD+
•Energy Payout Phase
•Oxidation of NAD+
•Substrate level
phosphorylation of
ATP
= NADH
NADH2
NADH2
NET GAIN
2 ATP
2 NADH
PYRUVATE
C-C-C
PYRUVATE
C-C-C
ANAEROBIC
RESPIRATION
(WITH OR
WITH OUT O2)
Coupled Reactions -
A chemical reaction having a common intermediate in which energy is
transfered from one side of the reaction to the other.
Examples:
1. The formation of ATP is endergonic and is coupled to the creation
of a proton gradient.
2. The energy of an exergonic reaction can be used to drive an
endergonic reaction
EX: Step 3 of glycolysis yields +3.0 kcal/mol of free energy; Step 4 has
a free energy of -9.0. Together = -6.0, so together they are strongly
exergonic – energy is released - passed to ATP!
END OF GLYCOLYSIS….
2 ATP’S USED -------- 4 ATP’S 2 net gain
+ 2 NAD+---- 2 NADH and 2 H+
1 GLUCOSE ------ 2 C3H4O3 (PYRUVIC ACID)
Prepartory Conversion Step
Prior to Krebs Citric Acid Cycle
Figure 9.10 Conversion of pyruvate to acetyl CoA, the junction between glycolysis and the Krebs cycle
MATRIX
PYRUVATE
C-C-C
MITOCHONDRIAL MEMBRANE
CO2
NAD+
MATRIX
NADH
Co
A
Acetyl CoA
Co
A
KREB’S CITRIC ACID CYCLE
Figure 9.11 A closer look at the Krebs cycle (Layer 1)
GLYCOLYSIS
MOVIE
Conversion
Thru
Krebs
Summary
Figure 9.11 A closer look at the Krebs cycle (Layer 2)
Figure 9.11 A closer look at the Krebs cycle (Layer 3)
Figure 9.11 A closer look at the Krebs cycle (Layer 4)
Figure 9.12 A summary of the Krebs cycle
NET GAIN PER PYRUVATE?
4 NADH
1 FADH2
1 ATP
X 2 TURNS ( 1 PER PYRUVATE)
8 NADH
2 FADH2
2 ATP
NET GAIN PER GLUCOSE? - so far….
10 NADH
2 FADH2
4 ATP
WHERE IS THE BIGGEST
PART OF THE ENERGY
NOW?
ELECTRON
TRANSPORT
SYSTEM
Figure 9.13 Free-energy change during electron transport
Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis
ETS
ETS w/
electrons
Proton/Electron
Accounting
Figure 9.14 ATP synthase, a molecular mill
ATP
SYNTHASE
WHAT’S
HAPPENING?
The Details of ATP
Syntase
COMPLETE CATABOLISM OF GLUCOSE REQUIRES 5 STEPS:
•GLYCOLYSIS-----GLUCOSE CONVERTED TO PYRUVIC ACID
•OXIDATION OF PYRUVIC ACID TO ACETYL CoA
•KREB’S CYCLE -CITRIC ACID CYCLE
•ELECTRON TRANSPORT CHAIN
•CHEMIOSMOSIS
Oxidative PhosphorylationRefers to the coupling of the electron transport chain to ATP
synthesis via the proton gradient and ATP synthase. This occurs
primarily in the presence of oxygen.
Chemiosmosisthe phosphorylation of ADP to ATP occurring when protons that
are following a concentration gradient contact ATP synthase.
From glycolysis
2 NADH
Protons pumped
ATP
8-12*
4-6*
2 ATP (substrate level
phosphorylation)
2
From bridge stage
2 NADH
12
From citric acid cycle
6 NADH
36
2 FADH2
8
2 ATP (substrate level
phosphorylation)
* The NADH that comes6from
glycolysis has to enter the
mitochondrion in order to
hand its electrons over to the
electron transport
18 a
system. There is usually
loss of energy involved in
4
doing this.
2
TOTAL
36-38
Figure 9.16 Review: how each molecule of glucose yields many ATP molecules during cellular respiration
FERMENTATION
Figure 9.x2 Fermentation
Figure 9.17a Fermentation
IN MOST
PLANTS
AND
MANY
MICROBES
Figure 9.17b Fermentation
IN ANIMALS
(MUSCLE)
AND
SOME
MICROBES
• LACTIC ACID AND ALCOHOL ARE STILL
RELATIVELY HIGH IN ENERGY.... AND CAN
EVENTUALLY UNDERGO AEROBIC
RESPIRATION TO RELEASE THIS ENERGY
AND CONVERT THEM TO CO2 AND H20.
• THE NET ENERGY YIELD FROM THE
ANAEROBIC RESPIRATION OF ONE
GLUCOSE MOLECULE IS 2 ATP MOLECULES.
Figure 9.18 Pyruvate as a key juncture in catabolism
Figure 9.19 The catabolism of various food molecules
Figure 9.20 The control of cellular respiration