1. Respiration Transforms Energy
Anaerobically (without O2):
4 ATP
Aerobically:
38 ATP

2. Glycolysis transforms nrg, but not efficiently
Transforms energy –
but low efficiency
2 ATP
• 686 kcal/glucose nets 2 ATP
• 7.3kcal/ATP e- e-
NADH
= < 4% of glucose’s
energy

3. Pyruvate options Anaerobic options EVERY ORGANISM FROM ALL KINGDOMS
E. coli
C. botulinum
YEAST & BACTERIA Staph spp
FROM ALL KINGDOMS
Some are facultative anaerobes – use O2 if present, but can grow without; others obligate anaerobes (no O2 tolerance)
Methanogens are obligate anaerobes (Archaea) that will not tolerate even brief exposure to air (O2). Anaerobic environments are plentiful, however, and include marine and fresh-water sediments, bogs and deep soils, intestinal tracts of animals, and sewage treatment facilities. Methanogens have an incredible type of metabolism that can use H2 as an energy source and CO2 as a carbon source for growth. In the process of making cell material from H2 and CO2, the methanogens produce methane (CH4) in a unique energy-generating process. The end product (methane gas) accumulates in their environment. Methanogen metabolism created most the natural gas (fossil fuel) reserves that are tapped as energy sources for domestic or industrial use.
ANIMAL

4. Mitochondria – Eukaryotic Site of Aerobic Respiration
• Glycolysis here
all organisms
• AEROBIC RESP:
Citric Acid Cycle
(Krebs) in MATRIX
ETC/Chemiosmosis
across CRISTAE

5. Aerobic Respiration Overview
many e-
link
rxn

6. Readying Pyruvate for The Krebs Cycle
In the mitochondria…
Each 3 C Pyruvate is modified into a 2 C Acetyl CoA e- e-
The 2 C are used to make 2 CO2
Pyruvate undergoes decarboxylation, releasing a C to CO2, and an H+ and 2e- to reduce NAD+ to NADH and leaving behind and acetyl group. After a series of modifications, the acetyl group combine with Coenzyme A to make acetyl coA.
Acetyl CoA is also produced from the metabolism of almost all organic fuels, including many lipids and proteins. Acetyl CoA is used in energy storage (lipid synthesis) as well as as Krebs. If ATP levels are high, Acetyl CoA is used to store energy as fats.
two glucose C
Again, e- are carried via NADH

7. The Krebs (aka Citric Acid) Cycle
…each
3 C pyruvate
into
acetyl CoA + oxaloacetate
= 6 C molecule
Each step produces
a modified product
via enzyme action
two more
glucose
C to CO2 per turn
More e- stripped off
for the e- transport
chain
In summary, three major events occur during the Krebs cycle. One GTP (guanosine triphosphate) is produced which eventually donates a phosphate group to ADP to form one ATP; three molecules of NAD are reduced; and one molecule of FAD is reduced. Although one molecule of GTP leads to the production of one ATP, the production of the reduced NAD and FAD are far more significant in the cell's energy-generating process. This is because NADH and FADH2 donate their electrons to an electron transport system that generates large amounts of energy by forming many molecules of ATP.
3 e- e-
ATP
NADH
FADH2

8. Another Electron Transfer Molecule
FAD +2 H  FADH2
• An inorganic cofactor
(recall CoA is an organic coenzyme)
• Both p+ and e- from 2 H are transferred
Transfer involves 2 H, but only 1 + and both e- transfer to NAD+.
H+ leftover is a free proton in the cytosol/whereever
Electron transfer reactions are the main function of NAD+. In cells, most oxidations are accomplished by the removal of hydrogen atoms. Each molecule of NAD+ can acquire two electrons; that is, be reduced by two electrons. However, only one proton accompanies the reduction. The other proton produced as two hydrogen atoms are removed from the molecule being oxidized is liberated into the surrounding medium. For NAD, the reaction is thus:
The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamide.
In metabolism, NAD+ is involved in redox reactions, carrying electrons from one reaction to another. The coenzyme is, therefore, found in two forms in cells: NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction forms NADH, which can then be used as a reducing agent to donate electrons. In organisms, NAD+ can be synthesized from simple building-blocks (de novo) from the amino acids tryptophan or aspartic acid. In an alternative fashion, more complex components of the coenzymes are taken up from food as the vitamin called niacin
Flavin adenine dinucleotide

9. Subtotal: 1 glucose through Krebs
ATP
ATP
Krebs/TCA
ATP
ATP
ATP
ATP
Glycolysis
Glucose -> pyruvate e- e- e- e- e- e- e- e- e- e- e- c c
Pyruvate ->acetyl CoA c c c e- c c

11. Final Step – ETC & Chemiosmosis
H from NADH/FADH2 lose e-, H+ build up across membrane
protons (H+) actively transported across
the membrane, producing a gradient
e- transport chain
through inner
membrane proteins
Chemiosmosis of
ions down the
gradient
H ion/NADH & FADH/TP ratios not 1:1; roughly 2.5 ATP/NADH and 1.5 ATP per FADH2.
Toxins can act to disrupt this step – cyanide, for example. Cyanide deactivates the enzyme cytochrome c oxidase. This is the last enzyme of the electron transport chain (the final step of cell respiration). The electron transport chain allows a great concentration of protons (H+ ions) to build up in the matrix of mitochondria so that they can diffuse back through a channel which in turn synthesises ATP. So basically cyanide stops the last step of cell respiration from occurring and as such inhibits ATP synthesis.
ATP
O2 to
H2O
production of ATP via
oxidative phosphorylation

12. Oxidative Phosphorylation requires O2
Production of ATP as OXYGEN is reduced
final electron acceptor
ATP
H ion/NADH & FADH/TP ratios not 1:1; roughly 2.5 ATP/NADH and 1.5 ATP per FADH2.
Toxins can act to disrupt this step – cyanide, for example. Cyanide deactivates the enzyme cytochrome c oxidase. This is the last enzyme of the electron transport chain (the final step of cell respiration). The electron transport chain allows a great concentration of protons (H+ ions) to build up in the matrix of mitochondria so that they can diffuse back through a channel which in turn synthesises ATP. So basically cyanide stops the last step of cell respiration from occurring and as such inhibits ATP synthesis.
O2 to
H2O

13. Result – Mass Production of ATP
(or thereabouts)
In glycolysis of cellular respiration, NADH produces 2ATP because one ATP is used to transport a molecule of NADH into the mitochondria and continue with aerobic respiration. However, in pyruvate decarboxylation and the Krebs cycle, each NADH yields 3ATPs. FADH2 yields 2 ATPs.
It is tempting to try to view the synthesis of ATP as a simple matter of stoichiometry (the fixed ratios of reactants to products in a chemical reaction). But (with 3 exceptions) it is not.
Most of the ATP is generated by the proton gradient that develops across the inner mitochondrial membrane. The number of protons pumped out as electrons drop from NADH through the respiratory chain to oxygen is theoretically large enough to generate, as they return through ATP synthase, 3 ATPs per electron pair (but only 2 ATPs for each pair donated by FADH2).
With 12 pairs of electrons removed from each glucose molecule,
* 10 by NAD+ (so 10x3=30); and
* 2 by FADH2 (so 2x2=4),
this could generate 34 ATPs.
Add to this the 4 ATPs that are generated by the 3 exceptions and one arrives at 38.
But
* The energy stored in the proton gradient is also used for the active transport of several molecules and ions through the inner mitochondrial membrane into the matrix.
* NADH is also used as reducing agent for many cellular reactions.
So the actual yield of ATP as mitochondria respire varies with conditions. It probably seldom exceeds 30.

14. Summary oxidized Each step generates e- transport molecules
net
Each step generates
e- transport molecules
Extra C become
waste (exhaled)
e- used to create a
concentration gradient
34?
Chemiosmosis
yields most ATP
reduced

15. Summary
net

16. Summary
generate
invest
2 ATP
38 ATP
oxidized
reduced

17. Glucose isn’t the only fuel (just the best)
Amino
acids
Sugars
Glycerol
Fatty
Glycolysis
Glucose
Glyceraldehyde-3- P
Pyruvate
Acetyl CoA
NH3
Citric
acid
cycle
Oxidative
phosphorylation
Fats
Proteins
Carbohydrates
Figure 9.19
Organic molecules other than
glucose simply enter the
pathway at different places
Monosaccharides in blood
stored carbs (glycogen)
stored fats (sub-cutaneous)
protein from tissues (!)