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Cell Respiration
Sources of Energy
• Sunlight and Food
– Both strive to provide cells with a source of
Glucose!
• Glucose holds 90 times the energy of an
ATP molecule.
– Glucose can release 3811 Calories
– Define calorie:
Cellular Respiration
• Instead of releasing all of the energy at
once (would be disastrous for the cell) in a
step-wise fashion.
• Glycolysis is the first step in this release of
energy.
• Glycolysis is the splitting of glucose to
create energy!!
• 6O2 + C6H12O6  6CO2 + 6H2O + Energy
Glycolysis
• Takes place in the cytoplasm.
– This should make sense! Why?
• Plant cell’s glucose is made where?
• Animal cell’s glucose comes from where?
• One molecule of Glucose is spit. 2 Pyruvic
Acid molecules are created.
• 1*(C6) = 6 Carbons
• 2*(C3) = 6 Carbons
Glycolysis – The Energy Carriers
• Creates ATP
• Also creates
NADH
• FADH2
•
Each time NADH or
FADH2 is created,
electrons are
transferred to create
the compound.
Glycolysis
• 1 Glucose
becomes 2
Pyruvic Acids.
• In order to
create energy,
Glycolysis
needs a
jumpstart.
– 2 ATP are put in to fuel
the reactions
– 4 ATP are made
– 2 NADH are made
– Net of 2 ATP
After Glycolysis
• Aerobic vs Anaerobic
• If Oxygen is present  Krebs Cycle + ETC
– Takes place in the mitochondria
• No Oxygen  Anaerobic Respiration
– Remains in the cytoplasm
Krebs Cycle
• In aerobic environments the second stage
of cell respiration takes place in the
mitochondria.
Krebs Cycle
• A. Before
Pyruvate enters
the Krebs Cycle
it has to be
prepared.
– Pyruvate is
brought into the
Mitochondria
– Pyruvate reacts
with Conzyme A
and NAD+ to
make Acetly
CoA, NADH
and releases
CO2
Krebs Cycle
• B. The prepared Pyruvate, now Acetyl CoA,
reacts with a 4C compound to make Citric
Acid(6C). NADH+ is also converted to NADH.
– Acetyl CoA 2C = 2C
– 4C compound = 4C
– Citric Acid Total = 6C
• C. Citric Acid is broken down to a 5C compound,
releasing CO2 and generating more NADH
–
–
–
–
Citric Acid = 6C
5C compound = 5C
1 CO2 = 1C
Total = 6C
Krebs Cycle
Krebs Cycle
• D. The 5C compound is broken down to a 4C
compound, making more CO2, NADH AND ATP.
–
–
–
–
5C compound = 5C
1CO2 = 1C
4C Compound = 4C
Total = 5C
• The 4C compound is transformed back into the
starting 4C compound, and produces FADH2.
Electron Transport Chain
• The molecules of ATP are used by the cell
for activities.
• The NADH and FADH2 made by the Krebs
Cycle are brought to the inner membrane
of the mitochondria where they are passed
down the electron transport chain.
• Ultimately, the end of the ETC ends with
Oxygen accepting the electrons and forms
water.
Electron Transport Chain
Electron Transport Chain
• As each complex passes the electrons
brought in by HADH and FADH2, H+ ions
are pumped into the intermembrane space
of the mitochondria.
• Just like with photosynthesis, these H+
ions are used to power ATP Synthase to
create ATP from ADP and phosphate in
the matrix.
Review
• H+ ions build up
between the
membranes.
• ATP is
synthesized in the
matrix!
• CO2 is released
Totals – 36 ATP FORMED!
• Glycolysis:
– 2 ATP formed
– 2NADH formed  6 ATP
• Each NADH makes 3 ATP
• 6 more ATP
• Krebs Cycle:
– 2 ATP are formed in the cycle
– 8 molecules of NADH are formed  24 ATP
• Each NADH generates 3 ATP
• 24 additional ATP formed
– 2 molecules of FADH2 are formed  4 ATP
• Each FADH2 generates 2 ATP
• 4 additional ATP formed
Fermentation
• When Oxygen is not present Glycolysis is
followed by another process.
Fermentation
Occurs!
During this
process, the lack
of Oxygen
prevents the
Pyruvic Acid from
entering the
mitochondria.
Instead, the
NADH produced
is recycled back
to NAD+
Fermentation
• Alcohol Fermentation: formation of ethyl alcohol
– Carried out by yeast.
– Used to make bread
– Pyruvic acid + NADH  alcohol + CO2 + NAD+
• Lactic Acid Fermentation: formation of lactic acid
– Overworked muscle cells do this!
– Used to make pickles and other foods
– Unicellular organisms use this process to make ATP
– Pyruvic acid + NADH  lactic acid + NAD+
Energy and Exercise
• Cells contain only a small
amount of available ATP.
This can only sustain them
for a few seconds.
• After a few seconds, the
only source of new ATP is
from lactic acid fermentation
(not enough Oxygen getting
to your cells).
• Cell Respiration is a slower
process, and can be used
to sustain energy over
longer periods.
Photosynthesis vs Cell Resp.
Photosynthesis
Function
Location
Reactants
Products
Equation
Cellular
Respiration