Examine the picture above.
1. Describe the cell membrane.
2. Does the above process use ATP?
3. Name the type of cellular transport being
shown above.
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Why do we need oxygen, and what purpose
do we need it for?

Cellular respiration is the process of
harvesting energy (ATP) from food on the
cellular level.

During cellular respiration, oxygen will be
added to glucose to make carbon dioxide and
water. See the formula below:
C6H12O6+ O2 → CO2 + H2O
◦ Note that this equation is almost the opposite of
the formula for photosynthesis!
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Cellular respiration takes place in the
mitochondrion.
Mitochondria are organelles that process ATP
from nutrients.
As stated before, mitochondria were once
living organisms.
◦ They have their own circular DNA.
◦ They can make their own protein, and divide like
bacteria.
◦ They have a double cell membrane.


The mitochondria
have both an outer
and an inner
membrane.
The space inside
the inner
membrane is called
the matrix. This is
the site of cellular
respiration.


The space in between
the outer and inner
membranes is called
the intermembranous
space.
This area is vital for
the electron
transport chain,
which we will talk
about later.

Note that the inner
membrane is folded
in upon itself. This
is to increase the
surface area of the
inner membrane.
◦ This also becomes
important when
discussing the
electron transport
chain.
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Cellular respiration is divided into several
phases, depending on the organism:
Eukaryotes:
◦ Glycolysis, the conversion of glucose to pyruvate.
◦ Krebs or TCA cycle, the oxidation of pyruvate.
(Electrons are loaded unto NADP+ at this time.)
◦ Electron transport chain, where the collected
electrons are used to “kick” protons out of the
matrix. The protons re-enter the matrix, which
charges ADP to ATP.
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Cellular respiration is divided into several
phases, depending on the organism:
Prokaryotes:
◦ Glycolysis, the conversion of glucose to pyruvate.
◦ Fermentation, the process of converting pyruvate to
acid and alcohol.

Prokaryotes conduct fermentation, as they
completely lack mitochondria.
◦ Be aware that eukaryotes also conduct fermentation
in the absence of oxygen. We’ll discuss that later.
Glycolysis
Mitochondria AND
oxygen present
Krebs cycle
Fermentation
No mitochondria, OR
no oxygen
Electron
transport
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Glycolysis is the
process of
converting glucose
to pyruvate.
In the process, both
2 ATP and 2NADPH
will be produced.
ATP is used for
energy, and NADPH
will be used later in
electron transport.
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Notice that ONE
molecule of pyruvate
is converted to TWO
molecules of
pyruvate.
This is important to
keep in mind when
we discuss the Krebs
cycle.
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
The Krebs/TCA/
citric acid cycle is
the set of reactions
that oxidizes
pyruvate.
Oxidation is the
harvesting of
electrons, so our
main product is
NADPH and FADH2.
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Note that this
process also
creates carbon
dioxide (CO2) as a
waste product.
You need to
remember that CO2
is released as a
waste product in
respiration!

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Also, note that each
molecule of
pyruvate makes 3
NADPH, 1 FADH2
and 1 ATP.
Since we had two
molecules of
pyruvate, we end
up with 6 NADPH, 2
FADH2 and 2 ATP.

The electron transport chain is the
process of harvesting energy from
collected electrons.

ALL of our collected electrons (e-) will be used
up to pump protons (p+) OUT of the matrix.
◦ Since we CANNOT destroy matter, the electrons
have to be disposed of. We bind them to oxygen
gas and add hydrogen, which creates water.
◦ This is why respiration requires oxygen!!!

The protons then re-enter the matrix through
an ion channel. This recharges ADP,
converting it to ATP.

Fermentation is the process of converting
pyruvate to acids, alcohols and other
compounds.
◦ This is a way of using up pyruvate WITHOUT the
addition of oxygen.

Fermentation is mainly conducted in bacteria
and yeast, and is the reason why we can
ferment drinking alcohol.
◦ However, eukaryotes can also conduct fermentation
– if they do NOT have access to oxygen!

In bacteria and yeast, alcohol is a very
common byproduct of fermentation.