Chapter 9: Cellular Respiration
and Fermentation
Section 1:
Cellular Respiration: An
Overview
A. Chemical Energy and Food
Respiration- Opposite of
Photosynthesis
– Breaks down the food
we eat into ATP for
cellular activity and
maintenance of
homeostasis
– Energy conversion:
– Sun Photosynthesis Glucose-RespirationEnergy
for Activity
ThereforePhotosynthesis:
Sunlight + CO2+ H2O---------C6H12O6 + 6O2
And……………..
Respiration:
C6H12O6 + 6O2------6CO2 + 6H20 +
ATP
Are energy conversions responsible
for converting……..(Finish this
statement )
B. Aerobic v Anaerobic Respiration
Respiration is responsible for producing
energy for cellular activity
It is much more efficient to break down
food in order to liberate energy in the
presence of OXYGEN
This means it is AEROBIC- with O2
Some organisms live in ANOXIC
environments (Without Oxygen)
These bacteria are known as
OBLIGATE ANAEROBES-oxygen is
harmful to them
Some anaerobes can survive for
short periods of time in the presence
of oxygenThey are called Facultative
Anaerobes
ex- Brewer’s Yeast
Most Aerobes can survive for very
short periods of time in low oxygen
conditions
People/Humans prefer to respire
aerobically- This is why we breathe!!
From time to time we respire
anaerobically- like after intense
exercise, like weight lifting and
sprinting- (This is why we are often
out of breathe afterwards)
When our bodies anaerobically
respire for too long we get cramps
due to build up of lactic acid
This does damage to tissue and will
not sustain us for long
C. Glycolysis!
Both Aerobic and Anaerobic
Respiration begin with Glycolysis!!
Glycolysis- breakdown of Glucose
When Glucose is broken down it
becomes a three Carbon molecule
called Pyruvate a.k.a Pyruvic Acid
• This takes place in the cytoplasm
(outside the Mitochondria)
Glycolysis
2 Phases:
Energy Investment
(It takes money to
make money)
Initial Cost of 2 ATP in
order to break apart
glucose
Energy Payoff- By
breaking down
glucose we form 4 ATP
Net Gain of 2 ATP
Glycolysis
Inputs of Glycolysis:
Glucose- all food is broken down
through digestion into simple
sugars such as glucose
ATP- Initial Energyto break apart
glucose into PGAL- Two 3 Carbon
Intermediates
• Outputs of Glycolysis
ATP- 2 ATP Molecules are produced
Two molecules of Pyruvate- Pyruvic Acid
2 Molecules of NADH- Electron carriers
Glycolysis
Glycolysis
The Fate of Pyruvic Acid depends on
the presence of Oxygen
– If O2 is present Aerobic Respiration
occurs aka Respiration
– If O2 absent- Anaerobic Repiration
occurs- aka Fermentation
D. Aerobic Cellular Repiration
Happens in the Presence of Oxygen
Begins with the products of Glycolysis: two
molecules of Pyruvic Acid (C-C-C)

The Pyruvic Acid diffuses into the Mitochondrial
Matrix and enters the Citric Acid Cycle- aka
Kreb’s Cycle
- In the CAC Pyruvic Acid is broken apart, one
Carbon at a time and released as CO2
- As it is broken energy is converted (2ADP2ATP)
and electron energy is stored (4NAD+--4NADH and FAD+ ----FADH)
- This happens twice ( 8 NADH and 2 FADH
Total- that is 20 Electrons)
1. Citric Acid Cycle
a.
b.
c.
Begins with Pyruvic Acid (C-C-C)
Enzymes remove 1
Carbon- leaving behind
a two carbon
compound called
Acetyl/Acetic Acid
This joins with another
enzyme (Co A) which
is 4 Carbons Long!
Becomes Acetyl Co A
(6 Carbons)
This makes it easier to separate the last two carbons
from Pyruvic Acid and expel them as CO2 while
stealing their energy in the form of electrons- Lots of
NADH and FADH
Citric Acid Cycle
Every time a Carbon
is removed- 2 High
Energy Electrons
are Freed and
stored by NAD and
FAD
Total ATP= 2
Total electron Pairs= 10
Remember- this happens twice!!! Glucose was broken down
into two mols of Pyruvic Acid!
Citric Acid Cycle
Inputs: 2 Pyruvic Acids (Glycolysis)
Outputs: CO2 (Expelled as waste)
2 ATP (very little energyused for cellular activity)
NADH and FADH (To be
used later in order to
make a lot of ATP)
All of these electrons are going to be
used during the next phase (Electron
Transport) to synthesize ATP
2. Electron Transport Chain (ETC)
a.
b.
c.
d.
e.
f.
Electrons carried to the inner
membrane by NADH and FADH
are dropped off at the beginning
As the electrons are passed
along, their energy is used to
pump H+ ions out of the matrix
and into the intermembrane space
creating a Conc. Gradient
The only way back into the matrix for H+ ions is through a
protein called ATP Synthase.
As H+ move through ATP Synthase like water through a dam,
energy is used to convert ADP to ATP.
Each pair of electrons can produce between two and three ATPs
(Depends on if they came from NADH or FADH)
9NADH= 28 ATP
2FADH= 4 ATP
Total of 32 ATPs created during ETC!!!!
Electron Transport Chain
and ATP Synthase
Total ATP Production
Glycolysis- 2 ATP
Citric Acid Cycle- 2ATP
Electron Transport-32 ATP
TOTAL= 36 ATP
Not bad for one molecule of glucose!!
D. Anaerobic Respiration
Occurs without Oxygen Present
Also known as “Fermentation”
Tequila
Beer
What do they all have in
common? (Three Things)
Fermentation
Whiskey
Cramping
Fermentation
1. Alcoholic Fermentation:
a. Occurs in Yeast when Oxygen is not present to
clear the ETC and CAC Cycle
b. Electrons cannot be passed into Kreb’s cycle so
they get passed back to Pyruvic Acid
c. Forms new products Ethyl Alcohol and Carbon
Dioxide
Alcoholic Fermentation
=
Pyruvic Acid
Ethyl Alcohol
Count the Atoms- What goes in
should come out!!!!
Carbon Dioxide
2. Lactic Acid Fermentation
a. Occurs in all animal species
b. When Oxygen is not present- electrons get passed back to
Pyruvic acid and attach in a different location (Look at
H’s)- Forms Lactic Acid
c. Responsible for muscle soreness and cramping
Lactic Acid Fermentation
=
Pyruvic Acid