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CELLULAR RESPIRATION
Biology 30
Mrs. S. Pipke-Painchaud
CELLULAR RESPIRATION SUMMARIZED
“An active cell in the body requires millions of
molecules of ATP per second to drive its biochemical
machinery.” (Purves, Orian and Heller)
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What is it?
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Where?
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is the process by which cells release energy from food molecules by a type
of controlled burning (food and oxygen enter the cell through the plasma
membrane by diffusion, passive transport, or active transport)
the series of reactions involved are controlled by Enzymes
Inside the mitochondria of a cell
Why?
C.R. releases the energy stored in the form of sugars (it is the opposite of
photosynthesis)
 It is an energy releasing reaction
 C.R. tries to release the greatest amount of energy possible; therefore, C.R.
tries to capture Energy in the form of ATP rather than heat which is a
waste (unusable form of energy)
 To avoid burning up this process captures energy in small, manageable
steps to avoid over heating and killing the cell.
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What organisms go through this process?
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Animals
Plants
THE GENERAL EQUATION . . .
enzymes
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C6H12O6 + 6O2  6 CO2 + 6 H2O + energy
(glucose)
I: GLYCOLYSIS
The First Step . . .
GLYCOLYSIS
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The Reaction:
C6H12O6 + 2 ATP  2 C3H4O3 + 4 ATP + 4 NADH
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it occurs in the Cytoplasm
it is an anaerobic reaction
it is a Reduction/Oxidation Reaction
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C6H12O6(glucose) splits to form 2  3 carbon units = C3H4O3
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Glucose  Pyruvic Acid (pyruvate)
C6H12O6 
C3H4O3
in order for the 6 C sugar to split it requires energy  2 ATP
if a reaction requires energy the energy is called Activation Energy
the breaking of the 6 C molecule and the several other reactions that occur in this step
produce a total of 4 ATP.
Therefore, there is a net gain of 2 ATP per reaction
GLYCOLYSIS . . .
C6H12O6 + 2 ATP  2 C3H4O3 + 4 ATP + 4 NADH
If the glucose molecule is split in half, what would you
expect the formula to be?
C6H12O6 split in half = C3H6O3
Actually = 2 C3H4O3
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** thus, we are missing _2__ hydrogens
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since matter can be neither created nor destroyed, the
cell uses H acceptors (carriers) to keep the H from
escaping.
Hydrogen carriers are called NAD+
(Nicotinamide Adenine Dinucleotide)
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Purpose: to function as a hydrogen acceptor and store the
hydrogen for later use (just like NADPH in photosynthesis)
GLYCOLYSIS REACTION SUMMARY:
II. INTERMEDIATE REACTION
~ OXIDATIVE DECARBOXYLATION
II. INTERMEDIATE REACTION
2 C3H4O3 + 2 O2  2 C2H3O3 + 2 CO2 + 2 NADH
If you examine the reactants what do you notice?
1)
Oxygen is now involved
2)
The carbon molecule in the reactants is the product of the last reaction.
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This reaction occurs in the Mitochondria (because this organelle has enzymes
that enable them to use oxygen safely)
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This is an aerobic reaction.
INTERMEDIATE REACTION
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Focus on . .. .CARBONS
C
C
C
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C
C
C
oxygen is used to remove Carbons from the
pyruvate
How many oxygens are used to do this?
2
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How many Carbon Dioxides does this produce?
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2
INTERMEDIATE REACTION
Focus on . . . HYDROGEN
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The number of Hydrogen in the reactants 8 :
the number of Hydrogens in the carbon
molecule on the products side = 6
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= a difference of 2
Thus, we need 2 hydrogen acceptors.
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2 NADH
INTERMEDIATE REACTION SUMMARY:
III: KREB’S CYCLE
OR
THE
CITRIC ACID CYCLE
III. KREB’S CYCLE
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Is a complex series of reactions, simplified for our
discussion to ….
2 C2H3O3 + 4 O2  4 CO2 + 2 ATP + 6 NADH
This reaction occurs in the
Mitochondria (because this organelle has the
enzymes that enable them to use oxygen)
This is an aerobic reaction.
III. KREB’S CYCLE
2 C2H3O3 + 4 O2  4 CO2 + 2 ATP + 6 NADH
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Focus on the ….. CARBONS
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What element is used to remove the Carbons?
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How many Oxygen are used to remove the
Carbons?
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Oxygen
4
As a result carbon dioxide is released to the
atmosphere through the stomata in the
leaves or when animals exhale.
III. KREB’S CYCLE
2 C2H3O3 + 4 O2  4 CO2 + 2 ATP + 6 NADH
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Focus on the . . . HYDROGENS
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The number of Hydrogen in the reactants
6: the number of Hydrogens in the carbon
molecule on the product side
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Thus, we need 6 hydrogen acceptors
III. KREB’S CYCLE
2 C2H3O3 + 4 O2  4 CO2 + 2 ATP + 6 NADH
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Focus on . . . Oxygen
How many oxygens are on the reactants side
of the equation?
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How many were used up in the formation of
CO2?
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14
8
How many oxygen are left?
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6
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These oxygen are immediately used in the next
reaction.
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FADH – (Flavin adenine dinucleotide) acts
as a hydrogen carrier of the free energy
produced by other reactions that happen
within the cell.
Depending on the textbook or website that
you read, they will incorporate this molecule
as well. We have just simplified.
INTERMEDIATE REACTION SUMMARY:
IV. ELECTRON TRANSPORT CHAIN
OR
OXIDATIVE
The Final Stage
PHOSPHORLATION
IV: ELECTRON TRANSPORT CHAIN
12 H + 6 O  6 H2O or 6 H2 + 3 O2  6 H2O
basically this transports H ions against the
concentration difference from the inner membrane
to the outer membrane of the mitochondria.
 It acts as a battery charger because the movement
of H+ ions creates a pH difference and causes an
electrical charge to build up
 The inner membrane has the enzyme (ATP
synthase) which allows protons back across the
nucleus and catalyzes the production of ADP to
ATP.
 Collects the most energy
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IV: ELECTRON TRANSPORT CHAIN
12 H + 6 O  6 H2O OR 6 H2 + 3 O2  6 H2O
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all of the carbons were lost in the last stage;
therefore, only Hydrogen and Oxygen remain.
At the end of the last reaction 6 oxygen were set
free
In order to prevent them from escaping, the
oxygen are immediately reused in the final
reaction.
12 H + 6O
IV: ELECTRON TRANSPORT CHAIN
12 H + 6 O  6 H2O OR 6 H2 + 3 O2  6 H2O
Total of Hydrogen Acceptors:
RXN
1:
__4__ NADH
2:
__2__ NADH
3:
__6__ NADH
TOTAL = 12
IV: ELECTRON TRANSPORT CHAIN
12 H + 6 O  6 H2O OR 6 H2 + 3 O2  6 H2O
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If you combine hydrogen and oxygen at a 2:1 ratio
you end up with
water.
*** This reaction releases 34 ATP***
ATP SUMMARY FOR CELLULAR REPIRATION
How much energy is released in total?
RXN
1:
__2__ ATP
2:
__0_ ATP
3:
__2_ ATP
4:
__34_ ATP
TOTAL = _________38___________ATP
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1 molecule of glucose produces 38 ATP
FINAL THOUGHTS
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If you release energy all at once it is similar to burning
glucose.
Just burning glucose all at once would release -686
kcal/mol of energy.
Burning a substances creates a lot of heat energy
Too much heat in the body will raise the body temperature
and cause some cells to be destroyed. (consider enzymes)
However, if each mole of ATP stores 12 Kcal of energy (36 X
12= 432 kcal eukaryotic respiration or 38 X 12 – 456 kcal
prokaryotic respiration)
Thus, the body uses a series of small manageable reactions,
in order to capture as much energy as possible without
harming the cell.
 The body is able to capture 44%of the energy as
ATP, but the other 56% is lost as heat.
ENERGY CONVERSIONS:
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if you look at conversion efficiencies, different phyla
use different amounts of energy.
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Amphibians use 50-75% of the energy from food that
they eat
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Reptiles use 50%
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Birds use 1%
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Mammals use 1.5%
Why the difference?
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Why are reptiles and amphibians 50 times more
efficient?
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Where do they live?
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Usually warm, tropical areas or very controlled environments
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Humans & birds live everywhere.
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Why?
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Reptiles and amphibians are cold blooded
“A poikilotherm is a plant or animal whose internal
temperature varies along with that of the ambient
environmental temperature. Most, but not all, terrestrial
ectotherms are poikilothermic. The opposite of poikilothermy
is homeothermy, referring to animals that maintain a
constant body temperature” (Wikipedia – Poikilotherm)
WHICH IS MORE EFFICIENT AEROBIC
RESPIRATION OR ANAEROBIC RESPIRATION?
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Anaerobic = Glycolysis = 2 ATP
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Aerobic = 34 – 36 ATP
WHAT HAPPENS
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WITHOUT OXYGEN IN OUR BODIES?
if we are deprived of oxygen for to long we will die because the cellular
respiration reactions are dependent on the oxygen carrying molecule.
Thus, without oxygen acceptors for carbon our bodies can’t get rid of the
electrons that are bound to certain compounds. All compounds quickly use up
the oxygen which leaves all the reduced compounds waiting to be oxidized.
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The chain reaction stops  we lack ATP  die
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Except for muscles which can get rid of their H atoms during glycolysis because
the H are passed back to pyruvate and lactic acid is formed.
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Glycolysis occurs at a faster pace when there is no oxygen
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It will continue until the lactic acid reaches toxic levels which will kill the cell.
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Nerve cells cannot do this; therefore, brain damage occurs very quickly.
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The anaerobic production of ATP is called fermentation.
FERMENTATION
~ producing energy without oxygen
ANAEROBIC RESPIRATION ~ FERMENTATION
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Occurs in the cytoplasm
Is similar to the first stage of cellular respiration,
Glycolysis, and does not require oxygen. (therefore it is
anaerobic.
It produces 2 ATP per molecule of glucose
If the body is severely taxed and it cannot supply enough
oxygen to carry out the next two steps of cellular
respiration.
The molecules of pyruvic acid are still being produced
Instead of continuing on to the next stage, Hydrogen is
added to the pyruvic acid, which in turn converts it to lactic
acid.
A lactic acid build up in muscles inhibits the muscle’s
ability to contract which causes fatigue (burning in the
muscles)
HUMANS . . .
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Many organisms will also ferment pyruvic acid
into, other chemicals, such as lactic acid.
Humans ferment lactic acid in muscles where
oxygen becomes depleted, resulting in localized
anaerobic conditions. This lactic acid causes the
muscle stiffness couch-potatoes feel after
beginning exercise programs. The stiffness goes
away after a few days since the cessation of
strenuous activity allows aerobic conditions to
return to the muscle, and the lactic acid can be
converted into ATP via the normal aerobic
respiration pathways.
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“Fermentation also occurs in some muscle cells,
which are also called twitch muscles, because
these muscles cannot store or use much oxygen in
comparison to the other muscles. When we run
the oxygen, supply of these muscles gets short as
a result of which the twitch muscles starts using
the fermentation of lactic acid. Through this
process, the muscles can go on functioning as
ATP is produced by the Glycolysis.”
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Anaerobic Respiration http://www.anaerobicrespiration.net/
LACTIC ACID FERMENTATION
FERMENTATION
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This process is also called anaerobic respiration.
The same process occurs in yeast except enzymes
within the yeast extract carbon dioxide and alcohol is
produced as a result.
What does carbon dioxide do?
 What industry uses fermentation?
 (Humans cannot ferment alcohol in their own bodies, we lack the
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genetic information to do so)
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Other Examples:
bread dough rises from ____________________ (the alcohol
evaporates during the cooking process)
 Bubbles in champagne
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ALCOHOL FERMENTATION
NOTE:
Anaerobic Respiration – works through the
cellular respiration pathway (Glycolysis)
 Fermentation – follows a similar format but ends
with the production of an alcohol which cannot be
transformed back.
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http://www.anaerobicrespiration.net/
FERMENTATION EXAMPLES . . .
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In a general sense, fermentation is the conversion of a carbohydrate such as sugar into an acid or an alcohol.
More specifically, fermentation can refer to the use of yeast to change sugar into alcohol or the use of
bacteria to create lactic acid in certain foods. Fermentation occurs naturally in many different foods given
the right conditions, and humans have intentionally made use of it for many thousands of years.
The earliest uses of fermentation were most likely to create alcoholic beverages such as mead, wine, and
beer. These beverages may have been created as far back as 7,000 BCE in parts of the Middle East. The
fermentation of foods such as milk and various vegetables probably happened sometime a few thousand
years later, in both the Middle East and China. While the general principle of fermentation is the same
across all of these drinks and foods, the precise methods of achieving it, and the end results, differ.
Beer is made by taking a grain, such as barley, wheat, or rye, germinating and drying it, and pulping it into
a mash. This mash is then mixed with hot water, and some fermentation begins. After being further treated,
the liquid is transferred to a fermentation vessel, where yeast is added to the mixture. This yeast “eats” the
sugar present in the mash and converts it into carbon dioxide and alcohol. After a few weeks of fermentation
and a further period of conditioning, the beer is ready to be filtered and consumed.
Wine is created using a similar method that also involves fermentation. Grapes are crushed to release the
sugar-rich juices, which are then either transferred quickly away from the skins or left to rest for a time to
absorb some of the flavor, tannins, and color of the skins. Yeast is then added, and the grape juice is allowed
to ferment for a number of weeks, at which point it is moved to different containers and fermented at a
slower rate, and eventually aged or bottled.
Pickling foods, such as cucumbers, may be accomplished by submerging the vegetable one wants to pickle in
a salty water solution with vinegar added. Over time, bacteria create the lactic acid that gives the food its
distinctive flavor and helps to preserve it. Other foods can be pickled simply by packing them in dry salt and
allowing a natural fermentation process to occur.
Milk can also be cultured, and people have been using fermentation with dairy products for nearly 5,000
years. It is speculated that early fermented dairy, such as yogurt, was the result of a natural process of
fermentation that occurred when the milk was cultured by bacteria that dwelt in skin sacks used to store
dairy. Yogurt these days is made by adding a number of special bacteria, such as L. acidophilus and L.
bulgaricus to milk and keeping it at the proper temperature. The bacteria begin converting the sugar in the
dairy to lactic acid, eventually creating what we know as yogurt.
WiseGeek: http://www.wisegeek.com/what-is-fermentation.htm
ARE YOU STILL ON THE BUS?
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Any Questions