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 All Organisms plants & animals
yeast
bacteria
muscle
cells

4. The Mitochondria - Site of Aerobic Respiration
• Glycolysis here
all organisms
• Aerobic Resp
Citric Acid Cycle
(Krebs) here
Electron Transport
across here

5. Aerobic Respiration Overview

6. Readying Pyruvate for The Krebs Cycle
Each 3 C Pyruvate is modified
into a 2 C Acetyl CoA
The 2 C are used to make 2 CO2 e-
Again, e- are carried via NADH
two glucose C

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.
ATP
NADH
FADH2

8. Subtotal: ATP ATP ATP ATP ATP ATP At this point: c c c c c c c c c e-

9. Final Step – e- Transport Chain
H from lose e-, build up across membrane
protons (H+) pumped across
the membrane producing a gradient
e- transport chain
through inner
membrane proteins
Chemiosmosis of
ions down the
gradient
ATP
Source of H?
production
of ATP

10. 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.

11. Summary – Know at least this much!
oxidized
Each step generates
e- transport molecules
Extra C become
waste (exhaled)
e- used to create a
concentration gradient
Chemiosmosis
yields most ATP
reduced