◦ Pyruvate oxidation
◦ Krebs cycle
◦ Electron Transport chain
All of our energy comes from?
This energy is the form of?
Plants convert this energy to?
The energy is potential (stored) energy stored in?
The energy is released by?
Most living organisms require energy in the form
Oxidation of sugars, primarily glucose.
Key chemical reactions = REDOX reactions,
transfer of electrons and H+
from one substance to
Energy is harvested from electrons and used to
ATP is stored in small quantities in cells but is
primarily produced on demand by cellular
ATP consists of three phosphate groups, ribose, and adenine.
ATP production: ADP + P → ATP; 2 types
◦ Substrate level phosphorylation
◦ Oxidative phosphorylation
2 types of Cellular Respiration
◦ Aerobic - oxygen is used as the final electron acceptor.
◦ Anaerobic – final electron acceptor is an inorganic
molecule; some bacteria and archaea.
Fermentation – is also an anaerobic process.
Summary of aerobic respiration using glucose:
C6H12O6 (glucose) + 6O2 → 6CO2 + 6H2O + energy
4 Steps, fig 9.8:
In the cytosol, 10 reactions, 3 stages, fig 9.13
◦ Glucose (6 C) is primed, using 2 ATP’s, and converted to
fructose 1,6 – bisphosphate.
◦ Fructose is split into two 3-C molecules, glyceraldehyde
◦ Energy extraction: electrons and H+
transferred to 2NAD+
and 4 ATPs produced. Final product – 2 pyruvate
molecules (3 C).
Glycolysis begins with an energy-
investment phase of 2 ATP
All 10 reactions of
What goes in:
What comes out:
The “2” indicates that glucose
has been split into two 3-carbon sugars
During the energy payoff phase, 4 ATP are produced for a net
gain of 2 ATP
Summary: Glucose + 2 NAD+ + 4ADP → 2
pyruvate + 2 NADH + 4ATP.
Note: each G3P is oxidized to produce 1 NADH
and 2 ATP by substrate level phosphoylation.
2 ATP are used to pay back 2 used at the
Net Production: Glucose + 2 NAD+ + 4ADP → 2
pyruvate + 2 NADH + **2ATP.
Fig 9.14. What inhibits glycolysis?Fig 9.14. What inhibits glycolysis?
Takes place in the outer membrane of the
mitochondria, fig 9.16 and 9.17.
Each pyruvate (3 C) is oxidized to an acetyl group
Each acetyl group is combined with Coenzyme A
(CoA) and feeds into the Kreb’s Cycle.
Summary: 2 Pyruvate + 2 CoA + 2 NAD+
+ 2acetyl CoA + 2NADH
Takes place in the matrix of the mitochondria, 9
reactions, 2 stages, fig 9.19.
Each acetyl CoA (2 C) combines with oxaloacetate (4 C) in
Kreb’s cycle to form citrate (6 C).
CoA removed and recycled.
2 stages cont’d
◦ Energy Extraction:
Oxidation reactions transfer electrons and H+
FADH. Each acetyl group that enters produces 3 NADH and
ATP produced by substrate level phosphorylation. Each
acetyl group produces 2 ATP.
Figure 9-19Figure 9-19
THE KREBS CYCLE
In each turn of the
cycle, the two
blue carbons are
converted to CO2
The two red
the cycle via
All 8 reactions of the
Krebs cycle occur in the
outside the cristae
In the next cycle, this
red carbon becomes
a blue carbon
So far we have 4ATP and a bunch of electrons
(energy) and H+
carried by NADH and FADH2.
NADH and FADH2 transfer electrons to the
transport chain (ETC) on the cristae of the
mitochondria, fig 9.24.
The ETC “harvests” the energy from the electrons
as they pass down the chain.
The energy harvested from the electrons is used
to “pump” H+
from the matrix to the intermembrane
space of the mitochondria (energy is stored in the
This produces a concentration gradient for H+
Occurs in the inner membrane
of the mitochondrion
reenter the matrix through the enzyme, ATP
ATP synthase recovers the energy and produces
ATP via oxidative phosphorylation.
Using the H+
gradient to produce ATP is called
transferred to O2 to produce H2O.
Summary: 10 NADH + 2 FADH2 + 3O2 → **26
ATP + 6H2O.
Add the 2 from glycolysis and 2 from the Kreb’s
cycle brings the total to 30 ATPs produced from
every glucose molecule.
Fate of pyruvate in the absence of oxygen.
Allows for ATP production on a small scale by
Metabolism = all of the chemical reactions in an
In the absence of available glucose, fats and
proteins can feed into glycolysis and the Kreb’s
Cycle, fig 9.29.
Products of glycolysis and the Kreb’s cycle can be
used to produce RNA/DNA, proteins and fats, fig