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Cellular Respiration
& Fermentation
4.4, 4.5, & 4.6
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4.4 – Overview of Cellular Respiration
 Key
Concept:
 The overall process of cellular respiration
converts sugar into ATP using oxygen.
4.5 – Cellular Respiration in Detail
 Key
Concept:
 Cellular respiration is an aerobic process
with two main stages.
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Purpose of Cellular Respiration
 To
make ATP from the energy stored in
glucose
 Glucose comes from an organism doing
photosynthesis themselves or from eating
foods containing glucose
 Remember: the purpose of
photosynthesis was just to get glucose
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Cellular Respiration has 2 parts
 Anaerobic
(does not require oxygen)
 Glycolysis
 Aerobic
(requires oxygen)
 Kreb’s Cycle (Citric acid Cycle)
 Electron Transport Chain (ETC)
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Glycolysis
 Takes
place in cytoplasm (eukaryotes and prokaryotes
do this step since all cells have cytoplasm)
 Splits
one glucose molecule into two pyruvate
molecules
 Costs the cell 2 ATP molecules to do this
4
ATP molecules are produced (only gain 2 ATP)
2
NADH molecules are formed
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Kreb’s Cycle (Citric Acid Cycle)
 Takes
place in matrix of mitochondria (only
in eukaryotes)
2
pyruvate (made during glycolysis) enter the
mitochondrion
 Each
pyruvate is broken down to create 1 ATP, 3 CO2,
NADH, & FADH2
 Total
products of Kreb’s cycle (because of 2 pyruvates):
 2 ATP
 6 CO2
 NADH
Will carry energy to the next step
 FADH2
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Electron Transport Chain (ETC)
 Takes
place in inner membrane of mitochondria (cristae)
 Folded to create more surface area for reactions to
produce more ATP in a small space
 NADH
& FADH2 (from Kreb’s) donate their energy (electrons)
to the electron transport chain
 Oxygen
ions
is the final electron acceptor and it picks up hydrogen
 Oxygen
and hydrogen ions combine to form water (released
as a waste product)
 32
ATP are made
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ATP from Cellular Respiration
4
from Glycolysis (uses up 2, so really only gain 2 ATP)
2
ATP from Kreb’s cycle
 32
ATP from ETC
 GAIN
36 ATP from one glucose molecule
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Equation for Cellular Respiration
C6H12O6 + 6O2
6CO2 + 6H2O + 36ATP
 Like the reverse of photosynthesis
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What happens when there’s no/not
enough oxygen or there are no
mitochondria?
 Answer: Fermentation
 Two
Kinds:
 Lactic Acid Fermentation
 Alcoholic Fermentation
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Allows glycolysis to continue
making ATP without oxygen
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Lactic Acid Fermentation
 Anaerobic
 Occurs
in muscle cells
 Produces burning feeling in muscles
 Occurs
when body is worked to the point that
more oxygen is being used than what is being
taken in
 This is why you breathe harder when
you’re exercising is to get more oxygen to
keep making ATP
 Produces
Lactic Acid and 2 (net) ATP
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Alcoholic Fermentation
 Anaerobic
 Occurs
in some bacteria and yeast
 Produces
 Used
CO2, ethyl alcohol, and 2 (net) ATP
in food production (bake bread and
make wine)