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Cellular Respiration
• Cellular respiration is the process by which
all organisms break down the food they
consume or create.
• The mitochondria break down food to
produce ATP in the cellular respiration
process. (Powerhouse)
Chemical Rxn of Respiration
6O2 + C6H12O6  6H2O + 6CO2 + Energy
(36 ATP)
Notice it is the opposite rxn of photosynthesis!!!
• 3 Stages of Cellular Respiration
– 1. Glycolysis – Anaerobic – No oxygen
needed
– If there is oxygen, continues to the step 2 & 3.
– If there is no oxygen, fermentation.
– 2. Citric Acid Cycle – Aerobic – Need Oxygen
– 3. Electron Transport Chain – Aerobic – Need
Oxygen
1st Step: Glycolysis
• “the splitting of glucose”
• All respiration processes begin here.
• Takes place in the cytoplasm.
• 2 molecules of ATP break glucose down
into Pyruvic Acid and release 4 molecules
of ATP. (Have to put in ATP to get more
out.)
• If no O  fermentation
Final products of Glycolysis
(per one glucose)
• 2 Pyruvic acids – Krebs Cycle
• 2 NADH – holds e- until Electron Tran
Chain
• 2 ATP
• Aerobic Res. produces a much larger
amount of ATP than fermentation, up to 20
times more ATP produced
Fermentation:
Anaerobic Respiration
• This is the next step, ONLY if no oxygen is
present.
• Fermentation does produce ATP, but only
a small amount. (2)
• Pyruvic Acid  produces Lactic Acid or
ethynol.
2 Types of Fermentation
• 1. Lactic Acid Fermentation: (muscle pain)
– Happens in fatigues muscle cells during periods of
strenuous exercise. The build up of lactic acid causes
a burning pain.
• 2. Alcoholic Fermentation
– Yeast and some bacteria can break down sugar to
produce ethanol, carbon dioxide, and energy
– Makes bread rise, alcoholic beverages, gasoline,
yogurt, cheese.
http://biology.clc.uc.edu/fankhauser
/cheese/CHEESE.HTML
• Dr. Fankhauser has a number of
fermentation-related recipes online,
complete with photographs:
• His main cheese page
http://biology.clc.uc.edu/fankhauser/cheese/CHEESE.HTML
Step 2: Krebs Cycle
or Citric Acid Cycle
• Similar to the Calvin Cycle.
• After Glycolysis, the Pyruvic acid molecules
move into the mito for further breakdown.
• Krebs is a biochemical pathway that breaks
down pyruvic acid, to make acetyl Co A, then
making 1 ATP, H ions, and 3CO2, 4 NADH,
1FADH2.
Continue Krebs Cycle
• In Prokaryotes – Krebs occurs in cell
membrane.
• In Eukaryotes – Krebs occurs in the inner
membrane of mitochondria. (matrix, more
surface area)
Final Products of 2 turns of the
Krebs Cycle from 2 pyruvic acids
So goes around 2 times!!
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2 ATP
8 NADH
2 FADH2
6 CO2
Step 3:
Electron Transport Chain
• Takes place in the inner membrane of the
mitochondria.
• Carrier proteins (blue)
• The ETC creates a high vs. low
concentration allowing the ATP Synthase
to begin working. Creating tons of ATP.
• For every pair of e- in the ETC = 3 ATP
Why do we need the Oxygen
• Oxygen serves as the final e- acceptor on
the ETC.
• Oxygen gets rid of low energy e- and H+
ions, the wastes of cellular res.
ETC Final Product
• 32 ATP
• Much more than any other cycle or system
Final Products of Cellular
Respiration (Aerobic)
• Through Aerobic Respiration a yield of 36
ATP can be produced from 1 glucose.
– 2 – Glycolysis
– 2 - Krebs cycle
– 32 - Electron Transport Chain
• Quick energy – lactic acid fermentation –
anaerobic
• Long lasting energy – aerobic cellular
respiration 3 steps.
• When beginning a race, our bodies will
use all 3 sources of ATP; ATP already in
the muscles, new ATP made by lactic acid
fermentation, and ATP made in Cellular
Respiration.
35-39% efficient.
The rest is lost as heat.
• Plants need to make ATP as well!!
• Other compounds come from the Krebs
Cycle. Example: amino acids, proteins,
ions.
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Plants Use Oxygen Too
You know that plants give off oxygen. But, there is a problem with knowing
that fact. Sometimes knowledge of one thing can interfere with knowing
something else. That's what happens in this case.
People who know that plants give off oxygen often assume that plants must
not also take it in. But this assumption is wrong. All living things--plants
included-- take in oxygen from the air.
Plant cells have special structures called chloroplasts--named for the
chlorophyll they contain. Plants use chlorophyll to capture energy from the
sun, then they use that energy to make food in a process called
photosynthesis.
The food is made by combining small molecules of water with small
molecules of carbon dioxide to make larger molecules of starch and sugar.
(Oxygen is released as a byproduct of photosynthesis.) The starch and
sugar are stored by the plant then used by us when we eat plants.
But feeding us is not why a plant goes to all the trouble of making starch
and sugar. Plants use the food they make to fuel their own growth and
activities. And that's where oxygen comes in again.
To "burn" fuel requires oxygen. Animals breathe in oxygen and use it to
extract energy from food. This process of using oxygen to release energy
from food is called respiration.
Plants use oxygen in exactly the same way! But when you have lots of
phytoplankton growing in water that's too warm to hold much oxygen, there
is little o no oxygen for fish. Algae Bloom.